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1.	He, Bin, et al. (author) Worldwide impacts of atmospheric vapor pressure deficit on the interannual variability of terrestrial carbon sinks 2022 In: National Science Review. - : Oxford University Press (OUP). - 2095-5138 .- 2053-714X. ; 9:4 Journal article (peer-reviewed)abstract Interannual variability of the terrestrial ecosystem carbon sink is substantially regulated by various environmental variables and highly dominates the interannual variation of atmospheric carbon dioxide (CO2) concentrations. Thus, it is necessary to determine dominating factors affecting the interannual variability of the carbon sink to improve our capability of predicting future terrestrial carbon sinks. Using global datasets derived from machine-learning methods and process-based ecosystem models, this study reveals that the interannual variability of the atmospheric vapor pressure deficit (VPD) was significantly negatively correlated with net ecosystem production (NEP) and substantially impacted the interannual variability of the atmospheric CO2 growth rate (CGR). Further analyses found widespread constraints of VPD interannual variability on terrestrial gross primary production (GPP), causing VPD to impact NEP and CGR. Partial correlation analysis confirms the persistent and widespread impacts of VPD on terrestrial carbon sinks compared to other environmental variables. Current Earth system models underestimate the interannual variability in VPD and its impacts on GPP and NEP. Our results highlight the importance of VPD for terrestrial carbon sinks in assessing ecosystems' responses to future climate conditions.
2.	Wang, Sifan, et al. (author) Fire carbon emissions over Equatorial Asia reduced by shortened dry seasons 2023 In: npj Climate and Atmospheric Science. - 2397-3722. ; 6:1 Journal article (peer-reviewed)abstract Fire carbon emissions over Equatorial Asia (EQAS) play a critical role in the global carbon cycle. Most regional fire emissions (89.0%) occur in the dry season, but how changes in the dry-season length affect the fire emissions remains poorly understood. Here we show that, the length of the EQAS dry season has decreased significantly during 1979–2021, and the delayed dry season onset (5.4 ± 1.6 (± one standard error) days decade−1) due to increased precipitation (36.4 ± 9.1 mm decade−1) in the early dry season is the main reason. The dry season length is strongly correlated with the length of the fire season. Increased precipitation during the early dry season led to a significant reduction (May: −0.7 ± 0.4 Tg C decade−1; August: −12.9 ± 6.7 Tg C decade−1) in fire carbon emissions during the early and peak fire season. Climate models from the Coupled Model Intercomparison Project Phase 6 project a continued decline in future dry season length in EQAS under medium and high-emission scenarios, implying further reductions in fire carbon emissions.
3.	Cai, Z., et al. (author) Amplified wintertime Barents Sea warming linked to intensified Barents oscillation 2022 In: Environmental Research Letters. - : IOP Publishing. - 1748-9318 .- 1748-9326. ; 17:4 Journal article (peer-reviewed)abstract In recent decades, the Barents Sea has warmed more than twice as fast as the rest of the Arctic in winter, but the exact causes behind this amplified warming remain unclear. In this study, we quantify the wintertime Barents Sea warming (BSW, for near-surface air temperature) with an average linear trend of 1.74 °C decade-1 and an interdecadal change around 2003 based on a surface energy budget analysis using the ERA5 reanalysis dataset from 1979-2019. Our analysis suggests that the interdecadal change in the wintertime near-surface air temperature is dominated by enhanced clear-sky downward longwave radiation (CDLW) associated with increased total column water vapor. Furthermore, it is found that a mode of atmospheric variability over the North Atlantic region known as the Barents oscillation (BO) strongly contributed to the BSW with a stepwise jump in 2003. Since 2003, the BO turned into a strengthened and positive phase, characteristic of anomalous high pressure over the North Atlantic and South of the Barents Sea, which promoted two branches of heat and moisture transport from southern Greenland along the Norwegian Sea and from the Eurasian continent to the Barents Sea. This enhanced the water vapor convergence over the Barents Sea, resulting in BSW through enhanced CDLW. Our results highlight the atmospheric circulation related to the BO as an emerging driver of the wintertime BSW through enhanced meridional atmospheric heat and moisture transport over the North Atlantic Ocean.
4.	Chen, Aifang, 1990, et al. (author) Large net forest loss in Cambodia's Tonle Sap Lake protected areas during 1992-2019 2022 In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 51, s. 1889-1903 Journal article (peer-reviewed)abstract Historical land-use practices have caused forest loss in Cambodia's Tonle Sap Lake area (TSLA), the largest freshwater lake in Southeast Asia. However, it remains unclear if this deforestation trend had continued since 2001 when the land was designated as protected areas. Using satellite imagery, we investigated forest conversion flows and fragmentation patterns in the TSLA for 1992-2001, 2001-2010, and 2010-2019, respectively. Results show substantial forest losses and fragmentations occurring at the lower floodplain where the protected areas are located until 2010, with some forest regain during 2010-2019. The land conversions indicated that forest clearing and agricultural farming were the primary causes for observed extensive forest loss during 1992-2010. Hence, despite the creating of protected areas in 2001, our findings reveal the persistence of alarming forest loss in the TSLA until 2010. On the other hand, while net forest loss has stopped after 2010, forest regain during 2010-2019 is way too small to restore the region's total forest area to even the level when the protected areas were established. Thus, more effective planning and implementations of forest management and restoration policies are needed for the TSLA.
5.	Chen, H., et al. (author) Intercomparison of ten ISI-MIP models in simulating discharges along the Lancang-Mekong River basin 2021 In: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 765 Journal article (peer-reviewed)abstract Water resources are of strategic importance for socioeconomic development. Many hydrological models (HMs) and land surface models (LSMs) have been developed for water resources assessment. However, systematic evaluation of discharge simulation from multiple models is still lacking in the Lancang-Mekong River basin. Here, we evaluated the performances of ten HMs and LSMs by evaluating their simulated discharge against observations at the basin scale. The selected models were within the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP2a) framework driven by Global Soil Wetness Project 3 (GSWP3) climate forcing data. Five discharge percentile series were used to evaluate the model performances for low, mean, and high flows. The intercomparison according to four statistical criteria revealed considerable differences exist in model performances for different discharge percentiles, indicating a large uncertainty caused by the choice of models with different degree of physical complexity and sensitivity to the quality of the input data. The models generally performed better for high flow than for low flow. Furthermore, the models generally performed better in downstream than in upstream, with the exception of close to the estuary, where complex processes involving interactions between freshwater and saline water are present. It is not surprising that the two calibrated model (WaterGAP2 and WAYS) are superior over the other models. This systematic intercomparison provides insights into the model behaviours and accuracies in discharges predicting with varying intensities, which can aid in quantifying uncertainties in water resources simulation at the basin scale. (C) 2020 Elsevier B.V. All rights reserved.
6.	Chen, Shiyin, et al. (author) Tree-ring recorded variations of 10 heavy metal elements over the past 168 years in southeastern China 2021 In: Elementa: Science of the Anthropocene. - : University of California Press. - 2325-1026. ; 9:1 Journal article (peer-reviewed)abstract Heavy metal pollution is a serious concern in the urban area of China. Understanding metal pollution history is crucial for setting up appropriate measures for pollution control. Herein, we report a record of concentrations of 10 heavy metals (Fe, Mn, Cu, Zn, Ni, Cr, Cd, Pb, Co, and Sr) in Pinus massoniana tree rings from Fuzhou City over the past 168 years, which represents the longest tree-ring chronology of heavy metals in China. The studied metals displayed contrasting distribution patterns. Among them, Mn and Sr showed the strongest migration trend with peak concentrations at the pith. Co, Cd, and Pb also showed distinctively high concentrations near the boundary between heartwood and sapwood. Ni, Cu, Cr, and Fe showed an increasing trend possibly due to migration toward bark caused by physiological activities and increasing tourism activities and traffic pollution. The other elements (Cr, Fe, and Zn) with low migration revealed the historical pollution possibly discharged by the Fuzhou Shipping Bureau and other anthropogenic activities. Strong correlations between Cu content and temperature were found, which provides an alternative tree-ring proxy for climate reconstruction. This study provides a long-term perspective of the joint impacts of physiological, environmental, and climatological factors on the concentrations of heavy metals in southeastern China.
7.	He, B., et al. (author) Lengthening Dry Spells Intensify Summer Heatwaves 2022 In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 49:19 Journal article (peer-reviewed)abstract A lengthening of dry spells (DSLs) has been reported by some regional studies, but its linkage with heatwaves via the feedback between soil moisture and air temperature is still not clear on the global and continental scales. Here we examine increases in the length of DSLs during summer over the global continents using in situ precipitation records. Globally, the average DSL has increased by 0.46 day/decade since the 1970s along with increased high-pressure anomalies which are found to be an important reason for the intensification of heatwaves as suggested by the robust and widespread relationships between the DSL and heatwave duration and severity in the northern extratropics. The average DSL associated with a heatwave declined over lands, implying a strengthening coupling between precipitation anomalies and heatwaves. The findings of this study suggest that the precipitation variations associated with changes in DSLs should be considered in attributions of temperature extremes.
8.	Liu, T., et al. (author) Teleconnections among tipping elements in the Earth system 2023 In: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 13, s. 67-74 Journal article (peer-reviewed)abstract Tipping elements are components of the Earth system that may shift abruptly and irreversibly from one state to another at specific thresholds. It is not well understood to what degree tipping of one system can influence other regions or tipping elements. Here, we propose a climate network approach to analyse the global impacts of a prominent tipping element, the Amazon Rainforest Area (ARA). We find that the ARA exhibits strong correlations with regions such as the Tibetan Plateau (TP) and West Antarctic ice sheet. Models show that the identified teleconnection propagation path between the ARA and the TP is robust under climate change. In addition, we detect that TP snow cover extent has been losing stability since 2008. We further uncover that various climate extremes between the ARA and the TP are synchronized under climate change. Our framework highlights that tipping elements can be linked and also the potential predictability of cascading tipping dynamics.
9.	Tang, R., et al. (author) Increasing terrestrial ecosystem carbon release in response to autumn cooling and warming 2022 In: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 12, s. 380-385 Journal article (peer-reviewed)abstract Despite overall warming, many regions in the Northern Hemisphere have been cooling in autumn. This cooling resulted in an increasing release of net CO2 2004-2018 as primary production decreased more than respiration in cooling and respiration increased more than production in warming areas. Part of the Northern Hemisphere has experienced widespread autumn cooling during the most recent decades despite overall warming, but how this contrasting temperature change has influenced the ecosystem carbon exchange remains unclear. Here, we show that autumn cooling has occurred over about half of the area north of 25 degrees N since 2004, producing a weak cooling trend over the period 2004-2018. Multiple lines of evidence suggest an increasing net CO2 release in autumn during 2004-2018. In cooling areas, the increasing autumn CO2 release is due to the larger decrease of gross primary productivity (GPP) growth than total ecosystem respiration (TER) growth suppressed by cooling. In the warming areas, TER increased more than GPP because the warming and wetting conditions are more favourable for TER growth than GPP increase. Despite the opposite temperature trends, there has been a systematic increase in ecosystem carbon release across the Northern Hemisphere middle and high latitudes.
10.	Wang, X. J., et al. (author) Contrasting characteristics, changes, and linkages of permafrost between the Arctic and the Third Pole 2022 In: Earth-Science Reviews. - : Elsevier BV. - 0012-8252. ; 230 Journal article (peer-reviewed)abstract Permafrost degradation poses serious threats to both natural and human systems through its influence on ecological-hydrological processes, infrastructure stability, and the climate system. The Arctic and the Third Pole (Tibetan Plateau, TP hereafter) are the two northern regions on Earth with the most extensive permafrost areas. However, there is a lack of systematic comparisons of permafrost characteristics and its climate and ecoenvironment between these two regions and their susceptibility to disturbances. This study provides a comprehensive review of the climate, ecosystem characteristics, ground temperature, permafrost extent, and active-layer thickness, as well as the past and future changes in permafrost in the Arctic and the TP. The potential consequences associated with permafrost degradation are also examined. Lastly, possible connections between the two regions through land-ocean-atmosphere interactions are explored. Both regions have experienced dramatic warming in recent decades, characterized by Arctic amplification and elevation-dependent warming on the TP. Permafrost temperatures have increased more rapidly in the Arctic than on the TP, and will likely be reinforced under a future high emission scenario. Near-surface permafrost extents are projected to shrink in both regions in the coming decades, with a more dramatic decline in the TP. The active layer on the TP is thicker and has substantially deepened, and is projected to thicken more than in the Arctic. Widespread permafrost degradation increases geohazard risk and has already wielded considerable effects on the human and natural systems. Permafrost changes have also exerted a pronounced impact on the climate system through changes in permafrost carbon and land-atmosphere interactions. Future research should involve comparative studies of permafrost dynamics in both regions that integrate long-term observations, high-resolution satellite measurements, and advanced Earth System models, with emphasis on linkages between the two regions.
11.	Wei, T., et al. (author) Quantitative Estimation of the Climatic Effects of Carbon Transferred by International Trade 2016 In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6 Journal article (peer-reviewed)abstract Carbon transfer via international trade affects the spatial pattern of global carbon emissions by redistributing emissions related to production of goods and services. It has potential impacts on attribution of the responsibility of various countries for climate change and formulation of carbon-reduction policies. However, the effect of carbon transfer on climate change has not been quantified. Here, we present a quantitative estimate of climatic impacts of carbon transfer based on a simple CO2 Impulse Response Function and three Earth System Models. The results suggest that carbon transfer leads to a migration of CO2 by 0.1-3.9 ppm or 3-9% of the rise in the global atmospheric concentrations from developed countries to developing countries during 1990-2005 and potentially reduces the effectiveness of the Kyoto Protocol by up to 5.3%. However, the induced atmospheric CO2 concentration and climate changes (e.g., in temperature, ocean heat content, and sea-ice) are very small and lie within observed interannual variability. Given continuous growth of transferred carbon emissions and their proportion in global total carbon emissions, the climatic effect of traded carbon is likely to become more significant in the future, highlighting the need to consider carbon transfer in future climate negotiations.
12.	Yao, Tandong, et al. (author) Recent Third Pole’s rapid warming accompanies cryospheric melt and water cycle intensification and interactions between monsoon and environment: multi-disciplinary approach with observation, modeling and analysis 2019 In: Bulletin of The American Meteorological Society. - 0003-0007 .- 1520-0477. ; :March, s. 423-444 Journal article (peer-reviewed)abstract The Third Pole (TP) is experiencing rapid warming and is currently in its warmest period in the past 2,000 years. This paper reviews the latest development in multidisciplinary TP research associated with this warming. The rapid warming facilitates intense and broad glacier melt over most of the TP, although some glaciers in the northwest are advancing. By heating the atmosphere and reducing snow/ice albedo, aerosols also contribute to the glaciers melting. Glacier melt is accompanied by lake expansion and intensification of the water cycle over the TP. Precipitation has increased over the eastern and northwestern TP. Meanwhile, the TP is greening and most regions are experiencing advancing phenological trends, although over the southwest there is a spring phenological delay mainly in response to the recent decline in spring precipitation. Atmospheric and terrestrial thermal and dynamical processes over the TP affect the Asian monsoon at different scales. Recent evidence indicates substantial roles that mesoscale convective systems play in the TP’s precipitation as well as an association between soil moisture anomalies in the TP and the Indian monsoon. Moreover, an increase in geohazard events has been associated with recent environmental changes, some of which have had catastrophic consequences caused by glacial lake outbursts and landslides. Active debris flows are growing in both frequency of occurrences and spatial scale. Meanwhile, new types of disasters, such as the twin ice avalanches in Ali in 2016, are now appearing in the region. Adaptation and mitigation measures should be taken to help societies’ preparation for future environmental challenges. Some key issues for future TP studies are also discussed.
13.	Zhong, Ziqian, 1995, et al. (author) Disentangling the effects of vapor pressure deficit on northern terrestrial vegetation productivity 2023 In: Science Advances. - 2375-2548. ; 9:32 Journal article (peer-reviewed)abstract The impact of atmospheric vapor pressure deficit (VPD) on plant photosynthesis has long been acknowledged, but large interactions with air temperature (T) and soil moisture (SM) still hinder a complete understanding of the influence of VPD on vegetation production across various climate zones. Here, we found a diverging response of productivity to VPD in the Northern Hemisphere by excluding interactive effects of VPD with T and SM. The interactions between VPD and T/SM not only offset the potential positive impact of warming on vegetation productivity but also amplifies the negative effect of soil drying. Notably, for high-latitude ecosystems, there occurs a pronounced shift in vegetation productivity's response to VPD during the growing season when VPD surpasses a threshold of 3.5 to 4.0 hectopascals. These results yield previously unknown insights into the role of VPD in terrestrial ecosystems and enhance our comprehension of the terrestrial carbon cycle's response to global warming.
14.	Cai, Ziyi, et al. (author) Arctic Warming Revealed by Multiple CMIP6 Models: Evaluation of Historical Simulations and Quantification of Future Projection Uncertainties 2021 In: Journal of Climate. - 0894-8755. ; 34:12, s. 4871-4892 Journal article (peer-reviewed)abstract The Arctic has experienced a warming rate higher than the global mean in the past decades, but previous studies show that there are large uncertainties associated with future Arctic temperature projections. In this study, near-surface mean temperatures in the Arctic are analyzed from 22 models participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6). Compared with the ERA5 reanalysis, most CMIP6 models underestimate the observed mean temperature in the Arctic during 1979–2014. The largest cold biases are found over the Greenland Sea the Barents Sea, and the Kara Sea. Under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios, the multimodel ensemble mean of 22 CMIP6 models exhibits significant Arctic warming in the future and the warming rate is more than twice that of the global/Northern Hemisphere mean. Model spread is the largest contributor to the overall uncertainty in projections, which accounts for 55.4% of the total uncertainty at the start of projections in 2015 and remains at 32.9% at the end of projections in 2095. Internal variability uncertainty accounts for 39.3% of the total uncertainty at the start of projections but decreases to 6.5% at the end of the twenty-first century, while scenario uncertainty rapidly increases from 5.3% to 60.7% over the period from 2015 to 2095. It is found that the largest model uncertainties are consistent cold bias in the oceanic regions in the models, which is connected with excessive sea ice area caused by the weak Atlantic poleward heat transport. These results suggest that large intermodel spread and uncertainties exist in the CMIP6 models’ simulation and projection of the Arctic near-surface temperature and that there are different responses over the ocean and land in the Arctic to greenhouse gas forcing. Future research needs to pay more attention to the different characteristics and mechanisms of Arctic Ocean and land warming to reduce the spread.
15.	Cai, Ziyi, et al. (author) Assessing Arctic wetting: Performances of CMIP6 models and projections of precipitation changes 2024 In: Atmospheric Research. - 0169-8095. ; 297 Journal article (peer-reviewed)abstract The Arctic region is experiencing a notable increase in precipitation, known as Arctic wetting, amidst the backdrop of Arctic warming. This phenomenon has implications for the Arctic hydrological cycle and numerous socio-ecological systems. However, the ability of climate models to accurately simulate changes in Arctic wetting has not been thoroughly assessed. In this study, we analyze total precipitation in the Arctic using station data, multiple reanalyses, and 35 models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). By employing the moisture budget equation and an evaluation method for model performance with ERA5 reanalysis as a reference, we evaluated the models' capability to reproduce past Arctic wetting patterns. Our findings indicate that most reanalyses and models are able to replicate Arctic wetting. However, the CMIP6 models generally exhibit an overestimation of Arctic wetting during the warm season and an underestimation during the cold season from 1979 to 2014 when compared to the ERA5 reanalysis. Further investigation reveals that the overestimation of wetting during the warm season is largest over the Arctic Ocean's northern part, specifically the Canadian Arctic Archipelago, and is associated with an overestimation of atmospheric moisture transport. Conversely, the models significantly underestimate wetting over the Barents-Kara Sea during the cold season, which can be attributed to an underestimation of evaporation resulting from the models' inadequate representation of sea ice reduction in that region. The models with the best performance in simulating historical Arctic wetting indicate a projected intensification of Arctic wetting, and optimal models significantly reduce uncertainties in future projections compared to the original models, particularly in the cold season and oceanic regions. Our study highlights significant biases in the CMIP6 models' simulation of Arctic precipitation, and improving the model's ability to simulate historical Arctic precipitation could reduce uncertainties in future projections.
16.	Cai, Z., et al. (author) Review of changes and impacts of the cryosphere under the background of rapid Arctic warming 2021 In: Journal of Glaciology and Geocryology. - 1000-0240. ; 43:3, s. 902-16 Journal article (peer-reviewed)
17.	Cai, Z. Y., et al. (author) Arctic Warming Revealed by Multiple CMIP6 Models: Evaluation of Historical Simulations and Quantification of Future Projection Uncertainties 2021 In: Journal of Climate. - : American Meteorological Society. - 0894-8755 .- 1520-0442. ; 34:12, s. 4871-4892 Journal article (peer-reviewed)abstract The Arctic has experienced a warming rate higher than the global mean in the past decades, but previous studies show that there are large uncertainties associated with future Arctic temperature projections. In this study, near-surface mean temperatures in the Arctic are analyzed from 22 models participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6). Compared with the ERA5 reanalysis, most CMIP6 models underestimate the observed mean temperature in the Arctic during 1979-2014. The largest cold biases are found over the Greenland Sea the Barents Sea, and the Kara Sea. Under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios, the multimodel ensemble mean of 22 CMIP6 models exhibits significant Arctic warming in the future and the warming rate is more than twice that of the global/Northern Hemisphere mean. Model spread is the largest contributor to the overall uncertainty in projections, which accounts for 55.4% of the total uncertainty at the start of projections in 2015 and remains at 32.9% at the end of projections in 2095. Internal variability uncertainty accounts for 39.3% of the total uncertainty at the start of projections but decreases to 6.5% at the end of the twenty-first century, while scenario uncertainty rapidly increases from 5.3% to 60.7% over the period from 2015 to 2095. It is found that the largest model uncertainties are consistent cold bias in the oceanic regions in the models, which is connected with excessive sea ice area caused by the weak Atlantic poleward heat transport. These results suggest that large intermodel spread and uncertainties exist in the CMIP6 models' simulation and projection of the Arctic near-surface temperature and that there are different responses over the ocean and land in the Arctic to greenhouse gas forcing. Future research needs to pay more attention to the different characteristics and mechanisms of Arctic Ocean and land warming to reduce the spread.
18.	Cai, Z. Y., et al. (author) Interdecadal variability of the warm Arctic-cold Eurasia pattern linked to the Barents oscillation 2023 In: Atmospheric Research. - : Elsevier BV. - 0169-8095. ; 287 Journal article (peer-reviewed)abstract Observed winter near-surface air temperature anomalies in the Northern Hemisphere have exhibited a warm Arctic-cold Eurasia (WACE) pattern with interdecadal variation in recent decades, but the exact mechanism behind WACE is still under debate. This study used reanalysis data and climate model simulations to investigate the interdecadal variability of the WACE pattern on a centennial scale, as well as the role of atmospheric circulations. It is found that the second mode of atmospheric variability over the North Atlantic-Arctic region, known as the Barents oscillation (BO), played a dominant role in regulating the interdecadal variability of WACE. The atmospheric circulation associated with the positive phase of the BO corresponds to an anomalous enhancement of the quasi-barotropic anticyclone near the southern Barents-Kara Seas (BKS) and the North Atlantic, as well as a weakening of the mid-latitude westerly jet. This atmospheric circulation anomaly favors the northward transport of atmospheric heat and moisture to the BKS from the mid-latitudes, resulting in an increased air temperature through downward longwave radiation. Concurrently cold air is transported from the polar region to Central Eurasia (CE), decreasing air temperature over CE. The amplified temperature anomaly dipole results in the decadal enhancement of the WACE pattern. The atmospheric circulation anomalies related to the negative phase of the BO are the opposite, which in turn leads to the decadal weakening of the WACE pattern. Our results further support the important role of internal atmospheric variability in the formation of WACE and emphasize that the atmospheric circulation associated with the BO is the main driver of WACE decadal variability over the past century.
19.	Chai, C. H., et al. (author) Future snow changes and their impact on the upstream runoff in Salween 2022 In: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 26:18, s. 4657-4683 Journal article (peer-reviewed)abstract Understanding the hydrological processes related to snow in global mountainous regions under climate change is necessary for achieving regional water and food security (e.g., the United Nation's Sustainable Development Goals 2 and 6). However, the impacts of future snow changes on the hydrological processes in the high mountains of the "Third Pole" are still largely unclear. In this study, we aimed to project future snow changes and their impacts on hydrology in the upstream region of the Salween River (USR) under two shared socioeconomic pathway (SSP) scenarios (SSP126 and SSP585) using a physically based cryosphere-hydrology model. We found that the climate would become warmer (0.2 degrees C per decade under SSP126 and 0.7 degrees C per decade under SSP585) and wetter (5mm per decade under SPP126 and 27.8mm per decade under SSP585) in the USR in the future under these two SSPs. In this context, the snowfall, snow cover, snow water equivalent, and snowmelt runoff are projected to exhibit significant decreasing trends during 1995-2100, and the decreases are projected to be most prominent in summer and autumn. The future (2021-2100) snowmelt runoff is projected to significantly increase in spring compared with the reference period (1995-2014), which would benefit the availability of water resources in the growing season. The annual total runoff would significantly increase in all of the future periods due to increased rainfall, which would increase the availability of water resources within the basin, but the high peak flow that occurs in summer may cause rain flooding with short duration and high intensity. Compared with the reference period (the contribution of snowmelt runoff to the total runoff was determined to be 17.5 %), the rain- and snow-dominated pattern of runoff would shift to a rain-dominated pattern after the near term (2021-2040) under SSP585, whereas it would remain largely unchanged under SSP126. Climate change would mainly change the pattern of the snowmelt runoff, but it would not change the annual hydrograph pattern (dominated by increased rainfall). These findings improve our understanding of the responses of cryosphere-hydrological processes under climate change, providing valuable information for integrated water resource management, natural disaster prevention, and ecological environmental protection at the Third Pole.
20.	Chen, Aifang, 1990, et al. (author) Assessing reliability of precipitation data over the Mekong River Basin: A comparison of ground-based, satellite, and reanalysis datasets 2018 In: International Journal of Climatology. - : Wiley. - 0899-8418. ; 38:11, s. 4314-4334 Journal article (peer-reviewed)abstract Accurate precipitation data are the basis for hydro-climatological studies. As a highly populated river basin, with the biggest inland fishery in Southeast Asia, freshwater dynamics is extremely important for the Mekong River Basin (MB). This study focuses on evaluating the reliability of existing gridded precipitation datasets both from satellite and reanalysis, with a ground observations-based gridded precipitation dataset as the reference. Two satellite products (Tropical Rainfall Measuring Mission [TRMM] and the Precipitation Estimation from Remote Sensing Information using an Artificial Neural NetworkClimate Data Record [PERSIANN-CDR]), as well as three reanalysis products (Modern-Era Retrospective analysis for Research and Applications [MERRA2], the European Centre for Medium-Range Weather Forecasts interim reanalysis [ERA-Interim], and the Climate Forecast System Reanalysis [CFSR]) were compared with the Asian PrecipitationHighly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE) over the MB. The APHRODITE was chosen as the reference for the comparison because it was developed based on ground observations and has also been selected as reference data in previous studies. Results show that most of the assessed datasets are able to capture the major climatological characteristics of precipitation in the MB for the 10-year study period (1998-2007). Generally, both satellite data (TRMM and PERSIANN-CDR) show higher reliability than reanalysis products at both spatial and temporal scales across the MB, with the TRMM outperforming when compared to the PERSIANN-CDR. For the reanalysis products, MERRA2 is more reliable in terms of temporal variability, but with some underestimation of precipitation. The other two reanalysis products CFSR and ERA-Interim are relatively unreliable due to large overestimations. CFSR is better positioned to capture the spatial variability of precipitation, while ERA-Interim shows inconsistent spatial patterns but more realistically resembles the daily precipitation probability. These findings have practical implications for future hydro-climatological studies.
21.	Chen, A. F., et al. (author) An analysis of the spatial variation of tropical cyclone rainfall trends in Mainland Southeast Asia 2023 In: International Journal of Climatology. - 0899-8418. ; 43:13, s. 5912-26 Journal article (peer-reviewed)abstract Tropical cyclones (TCs) and the associated rainfall (TCR) have received increasing attention because of their catastrophic damages. Due to the differences in TC characteristics and TCR in different ocean basins, the changes in TCR would be complicated for areas receiving TC landfalling from multi-basins. Therefore, separating TCR and TC characteristics from the formation basins can offer more insights for accurately evaluating TCR in the landfalling areas. Here we selected the TC-prone Mainland Southeast Asia (MSEA) to investigate changes in TCR regarding TC characteristics from the surrounding formation basins from 1983 to 2020. Results show that the interannual variability of the total TCs influencing MSEA (MSEA-ALL-TC) characteristics, including number, total duration, maximum intensity and accumulated cyclone energy, was dominated by the TCs originating from the Western North Pacific (WNP-TC). However, the total TCR was controlled by the TCs originating from the WNP and the South China Sea (SCS-TC), whose influence on TCR was concentrated in the eastern MSEA. TCR associated with TCs originating from the Bay of Bengal was relatively small and concentrated in the western MSEA. For the whole MSEA, the total TCR contributed up to 47% of the annual extreme rainfall amount. Annual TCR presented significant decreasing trends in the southeast MSEA, while increasing trends exist in the northeast. These contrasting trends are attributed to the reduced tendency of WNP-TC track density and the increased SCS-TC rainfall rate. We also found that the SCS-TC induced a higher rainfall rate than the other two basins. The TC characteristics of number, total duration, maximum intensity and accumulated cyclone energy were significantly correlated with TCR in each formation basin, with the highest correlation of the total duration. This study improves our understanding of the influence of changes in TC characteristics on TCR in the TC multi-source region.
22.	Chen, Aifang, 1990, et al. (author) Flood impact on Mainland Southeast Asia between 1985 and 2018 — The role of tropical cyclones 2020 In: Journal of Flood Risk Management. - : Wiley. - 1753-318X. ; 13:2 Journal article (peer-reviewed)abstract Floods are disastrous natural hazards accused of human live losses. As a flood‐prone area, Mainland Southeast Asia (MSEA) has often been hit by floods, resulting in the highest fatality in the world. Despite the destructive flood impacts, how has flood occurrence changed over the past decades, and to what extent did floods affect the MSEA are not yet clear. Using the Dartmouth Flood Observatory large flood data archive, we aim to assess the trend of flood occurrence in the MSEA in 1985–2018, and quantify the associated impacts on humans. Particularly, the contribution of tropical cyclone (TC) landfall induced floods (TCFloods) is quantified, because of the frequent TC landfalls. Results show that (a) occurrence and maximum magnitude of floods by all causes (ALLFloods) significantly increased (p <.01), but not for TCFloods; (b) On average, TCFloods accounted for 24.6% occurrence of ALLFloods; (c) TCFloods caused higher mortality and displacement rate than ALLFloods did. As low flood protection standards in Cambodia and Myanmar is considered a reason for high flood‐induced mortalities, building higher flood protection standards should be taken as a priority for mitigating potential flood impacts. With quantifying flood occurrence and impacts, this study offers scientific understandings for better flood risk management.
23.	Chen, Aifang, 1990, et al. (author) Multidecadal variability of the Tonle Sap Lake flood pulse regime 2021 In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 35:9 Journal article (peer-reviewed)abstract Tonle Sap Lake (TSL) is one of the world's most productive lacustrine ecosystems, driven by the Mekong River's seasonal flood pulse. This flood pulse and its long-term dynamics under the Mekong River basin's (MRB) fast socio-economic development and climate change need to be identified and understood. However, existing studies fall short of sufficient time coverage or concentrate only on changes in water level (WL) that is only one of the critical flood pulse parameters influencing the flood pulse ecosystem productivity. Considering the rapidly changing hydroclimatic conditions in the Mekong basin, it is crucial to systematically analyse the changes in multiple key flood pulse parameters. Here, we aim to do that by using observed WL data for 1960-2019 accompanied with several parameters derived from a Digital Bathymetry Model. Results show significant declines of WL and inundation area from the late 1990s in the dry season and for the whole year, on top of increased subdecadal variability. Decreasing (increasing) probabilities of high (low) inundation area for 2000-2019 have been found, in comparison to the return period of inundation area for 1986-2000 (1960-1986). The mean seasonal cycle of daily WL in dry (wet) season for 2000-2019, compared to that for 1986-2000, has shifted by 10 (5) days. Significant correlations and coherence changes between the WL and large-scale circulations (i.e., El Nino-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Indian Ocean Dipole (IOD)), indicate that the atmospheric circulations could have influenced the flood pulse in different time scales. Also, the changes in discharge at the Mekong mainstream suggest that anthropogenic drivers may have impacted the high water levels in the lake. Overall, our results indicate a declining flood pulse since the late 1990s.
24.	Chen, Aifang, 1990, et al. (author) Rising future tropical cyclone-induced extreme winds in the Mekong River Basin 2020 In: Science Bulletin. - : Elsevier BV. - 2095-9273 .- 2095-9281. ; 65:5, s. 419-424 Journal article (peer-reviewed)abstract © 2019 Science China Press The societal impact of extreme winds induced by tropical cyclones (TCs) is a major concern in the Mekong River Basin (MRB). Though no clear trend of landfalling TC intensity along the Vietnam coastline has been observed since the 1970s, climate models project an increasing TC intensity in the 21st century over the Western North Pacific, which is the primary TC source region influencing the MRB. Yet, how future TC activities will affect extreme winds quantitatively in the MRB remains unclear. By employing a novel dynamical downscaling technique using a specialized, coupled ocean-atmospheric model, shorter return periods of maximum wind speed in the MRB for 2081–2100 compared with 1981–2000 are projected based on five global climate models under the RCP8.5 scenario, suggesting increases in the future tropical cyclone intensity. The results point to consistently elevated future TC-related risks that may jeopardize sustainable development, disrupt food supply, and exacerbate conflicts in the region and beyond.
25.	Chen, Aifang, 1990, et al. (author) Tropical cyclone rainfall in the Mekong River Basin for 1983–2016 2019 In: Atmospheric Research. - : Elsevier BV. - 0169-8095. ; 226, s. 66-75 Journal article (peer-reviewed)abstract As home to about 70 million people, the Mekong River Basin (MRB), located in Mainland Southeast Asia, is often influenced by tropical cyclones (TCs) landfalling. The TCs not only cause flood and storm hazards, but also play important roles in providing freshwater resource and welcomed sediment transports. Our study focuses on the climatology of TCs and associated rainfall (TCR) in the MRB for 1983–2016. Results show that: (i) the mean landfall occurrence of TCs is 6.2 yr −1 , leading to 36.7 mm yr −1 of annual mean TCR (2.5% of the annual total precipitation), which mainly occur in monsoon-TC season (i.e., June–November); (ii) TCs highly concentrate on the lower eastern MRB, generating the largest TCR contribution of 12.4% to the annual total precipitation; (iii) the annual mean contribution of TCs induced extreme precipitation - R20mm and R50mm (days of heavy precipitation rate ≥20 mm day −1 and ≥50 mm day −1 , respectively) - to that from annual total precipitation is large in the lower eastern MRB; (iv) over 60% of the basin area is influenced by TCR on average; and (v) a significant weakening trend of the TC frequency has been observed. The present findings lay a foundation for further in-depth research of the potential influence of the dynamic TCs and the associated rainfall in the MRB. © 2019
26.	Chen, Deliang, 1961, et al. (author) Assessment of past, present and future environmental changes on the Tibetan Plateau 2015 In: Chinese Science Bulletin. - 1001-6538. Journal article (peer-reviewed)
27.	Chen, Deliang, 1961, et al. (author) Association between winter temperature in China and upper air circulation over East Asia revealed by Canonical Correlation Analysis 2003 In: Global and Planetary Change. ; 37, s. 315-325 Journal article (peer-reviewed)
28.	Chen, Deliang, 1961, et al. (author) Development and verification of a multiple regression downscaling model for monthly temperature in Sweden, in "Preliminary analysis and statistical downscaling of monthly temperature in Sweden" 1999 Reports (other academic/artistic)
29.	Chen, Deliang, 1961, et al. (author) Using the Köppen classification to quantify climate variation and change: an example for 1901-2010 2013 In: Environmental Development. - : Elsevier BV. - 2211-4645. ; 6, s. 69-79 Journal article (peer-reviewed)abstract The Köppen climate classification was developed based on the empirical relationship between climate and vegetation. This type of climate classification scheme provides an efficient way to describe climatic conditions defined by multiple variables and their seasonalities with a single metric. Compared with a single variable approach, the Köppen classification can add a new dimension to the description of climate variation. Further, it is generally accepted that the climatic combinations identified with the Köppen classification are ecologically relevant. The classification has therefore been widely used to map geographic distribution of long term mean climate and associated ecosystem conditions. Over the recent years, there has also been an increasing interest in using the classification to identify changes in climate and potential changes in vegetation over time. These successful applications point to the potential of using the Köppen classification as a diagnostic tool to monitor changes in the climatic condition over various time scales. This work used a global temperature and precipitation observation dataset to reveal variations and changes of climate over the period 1901–2010, demonstrating the power of the Köppen classification in describing not only climate change, but also climate variability on various temporal scales. It is concluded that the most significant change over 1901–2010 is a distinct areal increase of the dry climate (B) accompanied by a significant areal decrease of the polar climate (E) since the 1980s. The areas of spatially stable climate regions for interannual and interdecadal variations are also identified, which have practical and theoretical implications.
30.	Chen, Hans, 1988, et al. (author) A robust mode of climate variability in the Arctic: The Barents Oscillation 2013 In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 40:11, s. 2856-2861 Journal article (peer-reviewed)abstract The Barents Oscillation (BO) is an anomalous wintertime atmospheric circulation pattern in the Northern Hemisphere that has been linked to the meridional flow over the Nordic Seas. There are speculations that the BO has important implications for the Arctic climate; however, it has also been suggested that the pattern is an artifact of Empirical Orthogonal Function (EOF) analysis due to an eastward shift of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). In this study, EOF analyses are performed to show that a robust pattern resembling the BO can be found during different time periods, even when the AO/NAO is relatively stationary. This BO has a high and stable temporal correlation with the geostrophic zonal wind over the Barents Sea, while the contribution from the AO/NAO is small. The surface air temperature anomalies over the Barents Sea are closely associated with this mode of climate variability.
31.	Chen, L.-J., et al. (author) Regionalization of Precipitation Regimes in China 2009 In: Atmospheric and Oceanic Science Letters. ; 2:5, s. 301-307 Journal article (peer-reviewed)
32.	Chen, Tao, et al. (author) Comprehensive applicability evaluation of multi-source snow depth datasets over the Tibetan Plateau 2022 In: Journal of Glaciology and Geocryology. - 1000-0240. ; 44:3, s. 795-809 Journal article (peer-reviewed)abstract Snow cover over the Tibetan Plateau has an important impact on the regional climate and water cycle. At present, the existing snow cover datasets have great uncertainty across this region, so the applicability assessment is indispensable in order to make best use of the advantages and bypass the disadvantages. In this study, a comprehensive quantitative evaluation of multiple variables and multiple evaluation indicators was carried out for three snow depth datasets over the Tibetan Plateau against the meteorological station observations（OBS）. The three snow depth datasets include one passive microwave remote sensing dataset（CHE）and two reanalysis datasets（ERA5-Land and MERRA2）. The variables are the annual mean snow depth, the annual maximum snow depth, and the annual snow cover days. In addition, the evaluation indicators are seasonal cycle, climatology, maximum value, standard deviation, interannual variation, and trend. A rank score（RS）value of 0~1 is computed for each evaluation indicator of each variable, the larger value of RS indicate relatively better performance of a snow depth dataset. Assessment results imply that, comprehensively considered, MERRA2 exhibits best agreement with OBS, followed by ERA5-Land, and finally CHE. Evaluate based on the RS of each variable, MERRA2 shows better performance on annual maximum snow depth and annual snow cover days, CHE shows better performance on annual mean snow depth. Evaluate based on the RS of each evaluation indicator, CHE shows advantages in describing trend, ERA5-Land exhibits better agreement with OBS on interannual variation, and MERRA2 show better performance on the rest of the indicators including seasonal cycle, climatology, maximum value and standard deviation. The RS statistics in terms of regional average and spatial distribution show that CHE performs better in the former, and ERA5-Land performs better in the latter. On the other hand, there are obvious deficiencies in all three snow depth datasets. MERRA2 has insufficient ability to characterize the interdecadal variation in snow cover, and its qualitative results for trend in snow cover is inconsistent with OBS, the reason for the first deficiency needs to be further studied and the second deficiency may be mainly related to its simulation capability to precipitation trend. ERA5-Land significantly overestimates the snow cover over the Tibetan Plateau, this may be mostly related to its data assimilation scheme. CHE has poor ability to characterize the spatial distribution of snow cover, coarse spatial resolution of passive microwave remote sensing may be the main reason. The conclusions are only applicable to the central and eastern part of the Tibetan Plateau due to the scarcity of meteorological station in west part of the Tibetan Plateau. Based on the remote sensing and reanalysis data, there is great uncertainty in the trend of snow cover in the western part of the Tibetan Plateau. These systematic classification evaluation of the three representative snow depth datasets provides information on data selection and data refinement.
33.	Chen, Xuelong, et al. (author) Investigation of Precipitation Process in the Water Vapor Channel of the Yarlung Zsangbo Grand Canyon 2024 In: BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY. - 0003-0007 .- 1520-0477. ; 105:2 Journal article (peer-reviewed)abstract The Yarlung Zsangbo Grand Canyon (YGC) is an important pathway for water vapor transport from southern Asia to the Tibetan Plateau (TP). This area exhibits one of the highest frequencies of convective activity in China, and precipitation often induces natural disasters in local communities, which can dramatically affect their livelihoods. In addition, the produced precipitation gives rise to vast glaciers and large rivers around the YGC. In 2018, the Second Tibetan Plateau Scientific Expedition and Research Program tasked a research team to conduct an "investigation of the precipitation process in the water vapor channel of the Yarlung Zsangbo Grand Canyon" (INVC) in the southeastern TP. This team subsequently established a comprehensive observation system of land-air interaction, water vapor, clouds, and rainfall activity in the YGC. This paper introduces the developed observation system and summarizes the preliminary results obtained during the first two years of the project. Using this INVC observation network, herein, we focus on the development of rainfall events on the southeastern TP. This project also helps to monitor geohazards in the key area of the Sichuan-Tibet railway, which traverses the northern YGC. The observation datasets will benefit future research on mountain meteorology.
34.	Chen, Z., et al. (author) Deep learning projects future warming-induced vegetation growth changes under SSP scenarios 2022 In: Advances in Climate Change Research. - : Elsevier BV. - 1674-9278. ; 13:2, s. 251-257 Journal article (peer-reviewed)abstract Climate warming has been projected to enhance vegetation growth more strongly in higher latitudes than in lower latitudes, but different projections show distinct regional differences. By employing big data analysis (deep learning), we established gridded, global-scale, climate-driven vegetation growth models to project future changes in vegetation growth under SSP scenarios. We projected no substantial trends of vegetation growth change under the sustainable development scenario (SSP1-1.9) by the end of the 21st century. However, the increase of vegetation growth driven by climate warming shows distinct regional variability under the scenario representing high carbon emissions and severe warming (SSP5-8.5), especially in Northeast Asia where growth could increase by (6.00% ± 4.21%). This may be attributed to the high temperature sensitivities of the deciduous needleleaf forests and permanent wetlands in these regions. When the temperature sensitivity that is defined as permutation importance in deep learning is greater than 0.05, the increase in vegetation growth will be more prominent. In addition, an extreme temperature increase across grasslands, as well as changing land-use management in northern China may also influence the vegetation growth in the future. The results suggest that the sustainable development scenario can maintain stable vegetation growth, and it may be a reliable way to mitigate global warming due to potential climate feedbacks driven by vegetation changes in boreal regions. Deciduous needleleaf forests will be a centre of greening in the future, and it should become the focus of future vegetation dynamics modelling studies and projections. © 2022 The Authors
35.	Chen, Z., et al. (author) Modeling vegetation greenness and its climate sensitivity with deep-learning technology 2021 In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11:12, s. 7335-7345 Journal article (peer-reviewed)abstract Climate sensitivity of vegetation has long been explored using statistical or process-based models. However, great uncertainties still remain due to the methodologies’ deficiency in capturing the complex interactions between climate and vegetation. Here, we developed global gridded climate–vegetation models based on long short-term memory (LSTM) network, which is a powerful deep-learning algorithm for long-time series modeling, to achieve accurate vegetation monitoring and investigate the complex relationship between climate and vegetation. We selected the normalized difference vegetation index (NDVI) that represents vegetation greenness as model outputs. The climate data (monthly temperature and precipitation) were used as inputs. We trained the networks with data from 1982 to 2003, and the data from 2004 to 2015 were used to validate the models. Error analysis and sensitivity analysis were performed to assess the model errors and investigate the sensitivity of global vegetation to climate change. Results show that models based on deep learning are very effective in simulating and predicting the vegetation greenness dynamics. For models training, the root mean square error (RMSE) is <0.01. Model validation also assure the accuracy of our models. Furthermore, sensitivity analysis of models revealed a spatial pattern of global vegetation to climate, which provides us a new way to investigate the climate sensitivity of vegetation. Our study suggests that it is a good way to integrate deep-learning method to monitor the vegetation change under global change. In the future, we can explore more complex climatic and ecological systems with deep learning and coupling with certain physical process to better understand the nature. © 2021 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
36.	Collier, Emily, et al. (author) The first ensemble of kilometer-scale simulations of a hydrological year over the third pole 2024 In: Climate Dynamics. - 0930-7575 .- 1432-0894. Journal article (peer-reviewed)abstract An accurate understanding of the current and future water cycle over the Third Pole is of great societal importance, given the role this region plays as a water tower for densely populated areas downstream. An emerging and promising approach for skillful climate assessments over regions of complex terrain is kilometer-scale climate modeling. As a foundational step towards such simulations over the Third Pole, we present a multi-model and multi-physics ensemble of kilometer-scale regional simulations for the hydrological year of October 2019 to September 2020. The ensemble consists of 13 simulations performed by an international consortium of 10 research groups, configured with a horizontal grid spacing ranging from 2.2 to 4km covering all of the Third Pole region. These simulations are driven by ERA5 and are part of a Coordinated Regional Climate Downscaling EXperiment Flagship Pilot Study on Convection-Permitting Third Pole. The simulations are compared against available gridded and in-situ observations and remote-sensing data, to assess the performance and spread of the model ensemble compared to the driving reanalysis during the cold and warm seasons. Although ensemble evaluation is hindered by large differences between the gridded precipitation datasets used as a reference over this region, we show that the ensemble improves on many warm-season precipitation metrics compared with ERA5, including most wet-day and hour statistics, and also adds value in the representation of wet spells in both seasons. As such, the ensemble will provide an invaluable resource for future improvements in the process understanding of the hydroclimate of this remote but important region.
37.	Du, W. T., et al. (author) Can summer monsoon moisture invade the Jade Pass in Northwestern China? 2020 In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 55, s. 3101-3115 Journal article (peer-reviewed)abstract Heavy precipitation events are increasingly concerned because their significant contribution to annual precipitation in the Northwestern China, which might be related to invasion of summer monsoon moisture. It is interest whether or not the same is Jade Pass as being outside the control of the Asian summer monsoon. In this work, six heavy precipitation events were selected based on the 95 percentiles of the daily precipitation at the 12 weather stations around the Jade Pass from 1970-2000, with consideration of the influences of elevation. The event on June 19th, 2013 was chosen for a detailed examination due to the fact that the day has a large-scale precipitation as revealed by a gridded precipitation dataset over a large region. Using a Weather Research and Forecasting Model (WRF) simulation with high spatiotemporal resolution and in situ isotopic tracing (delta O-18, delta D), under a large-scale heavy precipitation event, this study provides ambitious view at the synoptic scale. A dramatic decrease in the delta O-18, delta D and deuterium (d)-excess of precipitation, very high relative humidity (98%), and reduced air temperature indicate that the precipitation was a result of long-distance-transported monsoon vapor. In addition, the slope of the local water meteoric line (LWML) of the precipitation for this event was very close to that of the global meteoric water line (GWML), indicating the source of moisture was from the ocean. Meanwhile, the WRF simulation confirms that the precipitation at the Jade Pass was not caused by local convection, but by summer monsoon. Both WRF simulation and isotopic tracing support the view that the monsoon moisture could invade Jade Pass at the synoptic scale and impact on precipitation, which need be further investigated.
38.	Ehlers, Todd A., et al. (author) Past, present, and future geo-biosphere interactions on the Tibetan Plateau and implications for permafrost 2022 In: Earth-Science Reviews. - : Elsevier BV. - 0012-8252. ; 234 Journal article (peer-reviewed)abstract Interactions between the atmosphere, biosphere, cryosphere, hydrosphere, and geosphere are most active in the critical zone, a region extending from the tops of trees to the top of unweathered bedrock. Changes in one or more of these spheres can result in a cascade of changes throughout the system in ways that are often poorly understood. Here we investigate how past and present climate change have impacted permafrost, hydrology, and ecosystems on the Tibetan Plateau. We do this by compiling existing climate, hydrologic, cryosphere, biosphere, and geologic studies documenting change over decadal to glacial-interglacial timescales and longer. Our emphasis is on showing present-day trends in environmental change and how plateau ecosystems have largely flourished under warmer and wetter periods in the geologic past. We identify two future pathways that could lead to either a favorable greening or unfavorable degradation and desiccation of plateau ecosystems. Both paths are plausible given the available evidence. We contend that the key to which pathway future generations experience lies in what, if any, human intervention measures are implemented. We conclude with suggested management strategies that can be implemented to facilitate a future greening of the Tibetan Plateau.
39.	Fang, Keyan, et al. (author) Co-varying temperatures at 200hpa over the Earth’s three poles 2021 In: Science China Earth sciences. - : Springer Science and Business Media LLC. - 1674-7313 .- 1869-1897. ; 64, s. 340-350 Journal article (peer-reviewed)abstract The Earth’s three poles, the North Pole, South Pole, and Third Pole (i.e., the Tibetan Plateau and its surroundings), hold the largest amount of fresh water on Earth as glaciers, sea ice, and snow. They are sensitive to climate change. However, the linkages between climate variations of the three poles, particularly between the South Pole and Third Pole, remain largely unknown. The temperatures at 200 hPa over the three poles are the highest in the summer and are less affected by surface conditions, which could reflect large-scale dynamic linkages. Temperatures at 200 hPa peak the three poles during their respective hemispheric summer and exhibit in-phase variations on interdecadal timescales (10-100 years). The 200 hPa temperatures over the North Pole and South Pole were significantly correlated with the Brewer-Dobson circulation (BDC), which transports stratospheric ozone poleward, heating the air at 200 hPa. Tropopause warming over the Third Pole was found to enhance the poleward BDC, particularly to the South Pole, linking the Third Pole’s climate to the other two poles. Additionally, the Interdecadal Pacific Oscillation (IPO) also exhibits links with the 200 hPa temperatures of the three poles.
40.	Fang, M., et al. (author) Arctic amplification modulated by Atlantic Multidecadal Oscillation and greenhouse forcing on multidecadal to century scales 2022 In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1 Journal article (peer-reviewed)abstract Enhanced warming in the Arctic (Arctic amplification, AA) in the last decades has been linked to several factors including sea ice and the Atlantic Multidecadal Oscillation (AMO). However, how these factors contributed to AA variations in a long-term perspective remains unclear. By reconstructing a millennial AA index combining climate model simulations with recently available proxy data, this work determines the important influences of the AMO and anthropogenic greenhouse gas forcing on AA variations in the last millennium, leading to identification of a significant downward trend of AA on top of a sustained strong AMO modulation at the multidecadal scales. The decreased AA during the industrial era was strongly associated with the anthropogenic forcing, proving the emerging role of the forcing in reducing the AA strength. Reconstructed Arctic amplification shows a significant downward trend over the past millennium which can to a large part be explained by the strength of the Atlantic Multidecadal Oscillation and recent anthropogenic greenhouse gas forcing.
41.	Gao, Ge, 1972, et al. (author) Spatial and temporal variations and controlling factors of potential evapotranspiration in China: 1956-2000 2006 In: Journal of Geographical Sciences. ; 16:1, s. 3-12 Journal article (peer-reviewed)
42.	Gao, Ge, 1972, et al. (author) Trend of potential evapotranspiration over china during 1956 and 2000 2006 In: Geographical Research. ; 25:3, s. 378-387 Journal article (peer-reviewed)
43.	Gao, Yanhong, et al. (author) Quantification of the relative role of land-surface processes and large-scale forcing in dynamic downscaling over the Tibetan Plateau 2017 In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 48:5, s. 1705-1721 Journal article (peer-reviewed)abstract © 2016 Springer-Verlag Berlin HeidelbergDynamical downscaling modeling (DDM) is important to understand regional climate change and develop local mitigation strategies, and the accuracy of DDM depends on the physical processes involved in the regional climate model as well as the forcing datasets derived from global models. This study investigates the relative role of the land surface schemes and forcing datasets in the DDM over the Tibet Plateau (TP), a region complex in topography and vulnerable to climate change. Three Weather Research and Forecasting model dynamical downscaling simulations configured with two land surface schemes [Noah versus Noah with multiparameterization (Noah-MP)] and two forcing datasets are performed over the period of 1980–2005. The downscaled temperature and precipitation are evaluated with observations and inter-compared regarding temporal trends, spatial distributions, and climatology. Results show that the temporal trends of the temperature and precipitation are determined by the forcing datasets, and the forcing dataset with the smallest trend bias performs the best. Relative to the forcing datasets, land surface processes play a more critical role in the DDM over the TP due to the strong heating effects on the atmospheric circulation from a vast area at exceptionally high elevations. By changing the vertical profiles of temperature in the atmosphere and the horizontal patterns of moisture advection during the monsoon seasons, the land surface schemes significantly regulate the downscaled temperature and precipitation in terms of climatology and spatial patterns. This study emphasizes the selection of land surface schemes is of crucial importance in the successful DDM over the TP.
44.	Gong, Lebing, et al. (author) Sensitivity of the Penman–Monteith reference evapotranspiration to key climatic variables in the Changjiang (Yangtze River) basin 2006 In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 329:3-4, s. 620-629 Journal article (peer-reviewed)abstract Sensitivity analysis is important in understanding the relative importance of climatic variables to the variation of reference evapotranspiration (ETref). In this study, a non-dimensional relative sensitivity coefficient was employed to predict responses of ETref to perturbations of four climatic variables in the Changjiang (Yangtze River) basin. ETref was estimated with the FAO-56 Penman–Monteith equation. A 41-year historical dataset of daily air temperature, wind speed, relative humidity and daily sunshine duration at 150 national meteorological observatory stations was used in the analysis. Results show that the response of ETref can be precisely predicted under perturbation of relative humidity or shortwave radiation by their sensitivity coefficients; the predictive power under perturbations of air temperature and wind speed depended on the magnitude of the perturbation, season and region. The prediction errors were much smaller than the seasonal and regional variation of their sensitivity coefficients. The sensitivity coefficient could also be used to predict the response of ETref to co-perturbation of several variables. The accuracy of the prediction increases from the lower to the upper region. Spatial variations of long-term average monthly and yearly sensitivity coefficients were obtained by interpolation of station estimates. In general, relative humidity was the most sensitive variable, followed by shortwave radiation, air temperature and wind speed. The actual rank of the four climatic variables in terms of their sensitivity varied with season and region. The large spatial variability of the sensitivity coefficients of all the climatic variables in the middle and lower regions of the basin was to a large extent determined by the distinct wind-speed patterns in those two regions.
45.	Gu, W., et al. (author) Development of a downscaling method in China regional summer precipitation prediction 2011 In: Acta Meteorlogica Sinaca. - : Springer Science and Business Media LLC. - 0894-0525 .- 2191-4788. ; 25:3, s. 303-315 Journal article (peer-reviewed)
46.	He, J., et al. (author) Development and Evaluation of an Ensemble-Based Data Assimilation System for Regional Reanalysis Over the Tibetan Plateau and Surrounding Regions 2019 In: Journal of Advances in Modeling Earth Systems. - 1942-2466. ; 11:8, s. 2503-2522 Journal article (peer-reviewed)abstract The Tibetan Plateau is regarded as the Earth's Third Pole, which is the source region of several major rivers that impact more 20% the world population. This high‐altitude region is reported to have been undergoing much greater rate of weather changes under global warming, but the existing reanalysis products are inadequate for depicting the state of the atmosphere, particularly with regard to the amount of precipitation and its diurnal cycle. An ensemble Kalman filter (EnKF) data assimilation system based on the limited‐area Weather Research and Forecasting (WRF) model was evaluated for use in developing a regional reanalysis over the Tibetan Plateau and the surrounding regions. A 3‐month prototype reanalysis over the summer months (June−August) of 2015 using WRF‐EnKF at a 30‐km grid spacing to assimilate nonradiance observations from the Global Telecommunications System was developed and evaluated against independent sounding and satellite observations in comparison to the ERA‐Interim and fifth European Centre for Medium‐Range Weather Forecasts Reanalysis (ERA5) global reanalysis. Results showed that both the posterior analysis and the subsequent 6‐ to 12‐hr WRF forecasts of the prototype regional reanalysis compared favorably with independent sounding observations, satellite‐based precipitation versus those from ERA‐Interim and ERA5 during the same period. In particular, the prototype regional reanalysis had clear advantages over the global reanalyses of ERA‐Interim and ERA5 in the analysis accuracy of atmospheric humidity, as well as in the subsequent downscale‐simulated precipitation intensity, spatial distribution, diurnal evolution, and extreme occurrence.
47.	Hu, Zengyun, et al. (author) CCHZ-DISO: A Timely New Assessment System for Data Quality or Model Performance From Da Dao Zhi Jian 2022 In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 49:23 Journal article (peer-reviewed)abstract With the rapid development of big data, assessment of data quality or model performance has become a hot scientific question. However, most existing lots of metrics focus on specific aspects of the assessment, and comprehensive assessment is rare. Therefore, it is very necessary to develop new assessment system. To address this problem, a new assessment system is constructed which is named after Chen, Chen, Hu, and Zhou (CCHZ)-distance between indices of simulation and observation (DISO) according to the contributions of Xi Chen, Deliang Chen, Zengyun Hu, and Qiming Zhou. CCHZ-DISO system builds on the Euclidean Distance and flexible determination of statistical metrics and their numbers. Due to its simplicity and flexibility, CCHZ-DISO can be readily and widely applied to any subject of science. Therefore, it follows the principle of the Chinese philosopher Lao Zi's Da Dao Zhi Jian which means that the most basic truth is very simple.
48.	Hu, Zengyun, et al. (author) DISO: A rethink of Taylor diagram 2019 In: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 39:5, s. 2825-2832 Journal article (peer-reviewed)abstract Climate models use quantitative methods to simulate the interactions of the important drivers of climate system, to reveal the corresponding physical mechanisms, and to project the future climate dynamics among atmosphere, oceans, land surface and ice, such as regional climate models and global climate models. A comprehensive assessment of these climate models is important to identify their different overall performances, such as the accuracy of the simulated temperature and precipitation against the observed field. However, until now, the comprehensive performances of these models have not been quantified by a comprehensive index except the existed single statistical index, such as correlation coefficient (r), absolute error (AE), and the root‐mean‐square error (RMSE). To address this issue, therefore, in this study, a new comprehensive index Distance between Indices of Simulation and Observation (DISO) is developed to describe the overall performances of different models against the observed field quantitatively. This new index DISO is a merge of different statistical metrics including r, AE, and RMSE according to the distance between the simulated model and observed field in a three‐dimension space coordinate system. From the relationship between AE, RMSE, and RMS difference (RMSD) (i.e., standard deviation [SD] of bias time series), the new index also has the information of RMSD which is the statistical index in Taylor diagram. An example is applied objectively to display the applications of DISO and Taylor diagram in identifying the overall performances of different simulated models. Overall, with the strong physical characteristic of the distance in three dimensional space and the strict mathematical proof, the new comprehensive index DISO can convey the performances among different models. It can be applied in the comparison between different model data and in tracking changes in their performances.
49.	Hu, Zengyun, et al. (author) “Dry gets drier, wet gets wetter”: A case study over the arid regions of central Asia 2019 In: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 39:2, s. 1072-1091 Journal article (peer-reviewed)abstract © 2018 Royal Meteorological Society The “dry gets drier, wet gets wetter” (DGDWGW) paradigm well describes the pattern of precipitation changes over the oceans. However, it has also been usually considered as a simplified pattern of regional changes in wet/dry under global warming, although GCMs mostly do not agree this pattern over land. To examine the validity of this paradigm over land and evaluate how usage of drought indices estimated from different hydrological variables affects detection of regional wet/dry trends, we take the arid regions of central Asia as a case study area and estimate the drying and wetting trends during the period of 1950–2015 based on multiple drought indices. These indices include the standardized precipitation index (SPI), the standardized precipitation evapotranspiration index (SPEI), the Palmer drought severity index (PDSI) and self-calibrating PDSI (sc_PDSI) with both the Thornthwaite (th) and Penman–Monteith (pm) equations in PDSI calculation (namely, PDSI_th, PDSI_pm, sc_PDSI_th and sc_PDSI_pm). The results show that there is an overall agreement among the indices in terms of inter-annual variation, especially for the PDSIs. All drought indices except SPI show a drying trend over the five states of central Asia (CAS5: including Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan). The four PDSIs and SPEI reveal a wetting tendency over the northwestern China (NW; including Xinjiang Uygur Autonomous Region and Hexi Corridor). The contrasting trends between CAS5 and NW can also be revealed in soil moisture (SM) variations. The nonlinear wet and dry variations are dominated by the 3–7 years oscillations for the indices. Relationships between the six indices and climate variables show the major drought drivers have regional features: with mean temperature (TMP), precipitation total (PRE) and potential evapotranspiration (PET) for CAS5, and PRE and PET for NW. Finally, our analyses indicate that the dry and wet variations are strongly correlated with the El Niño/Southern Oscillation (ENSO).
50.	Hu, Z. Y., et al. (author) Evaluation of three global gridded precipitation data sets in central Asia based on rain gauge observations 2018 In: International Journal of Climatology. - : Wiley. - 0899-8418. ; 38:9, s. 3475-3493 Journal article (peer-reviewed)abstract The accuracies of gridded precipitation data sets are important for regional climate studies and hydrological models. In this study, the performances of Global Precipitation Climatology Centre (GPCC) V7, Climatic Research Unit (CRU) TS 3.22 and Willmott and Matsuura (WM) precipitation data sets were examined over central Asia by comparing them against observed precipitation records (OBS) from 586 meteorological stations during 1901-2010. The results show that all the three gridded data sets underestimated the observed precipitation at annual and monthly scales, especially in mountainous areas. Both GPCC and WM underestimated seasonal precipitation, especially for spring precipitation. Among the three gridded data sets, GPCC had the highest correlation and lowest bias compared with CRU and WM when against the OBS. WM had a higher correlation than that of CRU, and its bias was larger than that of CRU. In terms of the drought and heavy rainfall events, CRU had the best performance in capturing drought events, and GPCC was best at representing heavy rainfall events. These differences in the performances between the three gridded data sets were primarily induced by their different interpolation methods and the numbers of available meteorological stations used in the interpolations of the three gridded data sets. Therefore, compared to the other two data sets, GPCC is more suitable for studies of long-term precipitation variations over central Asia.

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