| 1. |
- Chen, H., et al.
(author)
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Intercomparison of ten ISI-MIP models in simulating discharges along the Lancang-Mekong River basin
- 2021
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 765
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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.
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| 2. |
- He, B., et al.
(author)
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Lengthening Dry Spells Intensify Summer Heatwaves
- 2022
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In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 49:19
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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.
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| 3. |
- Chen, A. F., et al.
(author)
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An analysis of the spatial variation of tropical cyclone rainfall trends in Mainland Southeast Asia
- 2023
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In: International Journal of Climatology. - 0899-8418. ; 43:13, s. 5912-26
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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.
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| 4. |
- Chen, Aifang, 1990, et al.
(author)
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Multidecadal variability of the Tonle Sap Lake flood pulse regime
- 2021
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In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 35:9
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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.
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| 5. |
- Liu, B., et al.
(author)
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Global and Polar Region Temperature Change Induced by Single Mega Volcanic Eruption Based on Community Earth System Model Simulation
- 2020
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In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 47:18
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Journal article (peer-reviewed)abstract
- In order to understand the pure long-term influence of single mega volcanic eruption (SMVE) of universal significance on global and polar region temperature changes, the AD 1258 Samalas mega volcanic eruption in Indonesia which is the largest eruption over the past millennium is selected as an ideal eruption for simulation study based on Community Earth System Model. Both reconstructions and simulations show that the Northern Hemisphere experienced nearly two decades of strong cooling after the Samalas mega eruption. The significant cooling in the Arctic lasts for 16 years, while the cooling in the Antarctic lasts only 2 years. As the volcanic aerosol gradually disappears, stronger cooling occurs in Arctic winter, and warming occurs in Antarctic winter. This asymmetric temperature changes over Arctic and Antarctic after SMVE (such as Samalas) are caused by the combined effects of albedo feedback and ocean-atmosphere heat exchange related to sea ice.
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| 6. |
- Sun, W. Y., et al.
(author)
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How Northern High-Latitude Volcanic Eruptions in Different Seasons Affect ENSO
- 2019
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In: Journal of Climate. - : American Meteorological Society. - 0894-8755 .- 1520-0442. ; 32:11, s. 3245-3262
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Journal article (peer-reviewed)abstract
- The impact of northern high-latitude volcanic (NHV) eruptions on El Nino-Southern Oscillation (ENSO) is investigated based on ensemble simulations with the Community Earth System Model. The seasonality of the atmospheric circulation influences the NHV aerosol dispersion, causing stronger (weaker) Northern Hemisphere cooling after the January and April (July and October) eruptions. ENSO's response is found to be more dependent on NHV eruption seasons than that on tropical eruption seasons. The January eruption causes an El Nino in an eruption year [year (0) hereafter] while an El Nino occurs in year (1) after the October eruption. No significant El Nino occurs after the April (July) eruption. A diagnostic analysis reveals that these El Ninos' developments are attributed to the positive zonal, meridional advective, and thermocline feedbacks, triggered by the western Pacific westerly anomalies. The anomalous North Pacific cyclone (NPC) and Asian monsoon are key systems to excite anomalous westerlies, which are caused by the NHV-induced midlatitude cooling and Eurasian continent-North Pacific thermal contrast. After the January eruption, the anomalous NPC develops in early summer and connects with a weakened Asian summer monsoon, which excites anomalous westerlies over the Indo-western Pacific, activating the Bjerknes feedback. For the October eruption, the anomalous NPC and enhanced East Asian winter monsoon bring cold air to the Maritime Continent and warm the subtropical central North Pacific through surface heat flux exchange, exciting the westerly anomalies. These results suggest that the strong dependence on the seasonal timing of NHV should be a critical element of data-model comparisons.
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| 7. |
- Zeng, Z. Z., et al.
(author)
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A reversal in global terrestrial stilling and its implications for wind energy production
- 2019
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In: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 9:12, s. 979-985
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Journal article (peer-reviewed)abstract
- Wind power, a rapidly growing alternative energy source, has been threatened by reductions in global average surface wind speed, which have been occurring over land since the 1980s, a phenomenon known as global terrestrial stilling. Here, we use wind data from in situ stations worldwide to show that the stilling reversed around 2010 and that global wind speeds over land have recovered. We illustrate that decadal-scale variations of near-surface wind are probably determined by internal decadal ocean-atmosphere oscillations, rather than by vegetation growth and/or urbanization as hypothesized previously. The strengthening has increased potential wind energy by 17 +/- 2% for 2010 to 2017, boosting the US wind power capacity factor by similar to 2.5% and explains half the increase in the US wind capacity factor since 2010. In the longer term, the use of ocean-atmosphere oscillations to anticipate future wind speeds could allow optimization of turbines for expected speeds during their productive life spans.
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| 8. |
- Chai, J., et al.
(author)
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A robust equatorial Pacific westerly response to tropical volcanism in multiple models
- 2020
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In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 55
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Journal article (peer-reviewed)abstract
- After each of the 1963 Agung, 1982 El Chichon, and 1991 Pinatubo eruptions, an El Nino was observed. The increased likelihood of an El Nino after a tropical eruption has also been found in long-term reconstructed proxy data. Through examining simulations over the last millennium by 11 different models, we show that a tropical volcano eruption can robustly excite a western-to-central equatorial Pacific (WCEP) westerly anomaly at 850 hPa in eight out of the 11 models; such a westerly anomaly is favorable for El Nino development. Under the volcanic forcing, there are significant extratropical continent surface cooling and tropical drying with negative precipitation anomalies over the South-South East Asia (SSEA), West African monsoon, and Intertropical Convergence Zone (ITCZ) regions. This common precipitation suppression response occurs in most of the models. Sensitivity experiments show that a WCEP westerly anomaly can be excited by the tropical land cooling, especially the SSEA cooling induced precipitation suppression rather than by the extratropical land surface cooling. Theoretical results show that a WCEP westerly anomaly is excited due to a Gill response to reduced precipitation over the SSEA and West African monsoon regions; and the SSEA contributes more than the West African monsoon does. The ITCZ weakening, however, excites an easterly wind anomaly. The models with more sensitive convective feedback tend to simulate an El Nino more easily, while a failed simulation of an El Nino after a robust westerly anomaly in some models calls for further studies on these models' delayed responses to radiative forcing induced by volcano eruptions.
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| 9. |
- Gu, X., et al.
(author)
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Impacts of anthropogenic warming and uneven regional socio-economic development on global river flood risk
- 2020
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 590
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Journal article (peer-reviewed)abstract
- Employing a multi-model framework, we estimate the impacts of contrasting warming levels and uneven regional socio-economic development on area, population and gross domestic product (GDP) exposures to flood magnitude and variability in global Flood-Affected Regions (FARs). These exposures to flood variability show persistent increases in FARs, but to flood magnitude only in East and South Asia. Globally, the increases in these exposures are not projected in moderate but extreme floods. Specifically, the areal exposure would be decreased (increased) by 1.8%/°C (1.9%/°C) for moderate (extreme) floods; the reduced population exposure to extreme floods can be three times higher than that to moderate floods when limiting 2 °C to 1.5 °C warming. Rapid regional economic growth of East and South Asia (whose GDP accounts for 9.8% of FARs in year 2000 to 18.5% in year 2025) would shift global GDP exposure from a decrease of 2.5%/°C to an increase of 1.7%/°C. © 2020 Elsevier B.V.
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| 10. |
- Guo, L. L., et al.
(author)
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Links between global terrestrial water storage and large-scale modes of climatic variability
- 2021
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 598
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Journal article (peer-reviewed)abstract
- Large-scale states of ocean and atmosphere control the quantity and routine of vapor transported into land and the land water storage pattern. However, the contributions of leading climatic modes, or teleconnections (TCs), to global terrestrial water storage (TWS) variations are poorly understood. Here, we use measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to study 14 main TC controls on river basins and continental and global water storage patterns. Variations in terrestrial water storage anomaly (TWSA) in>97.5% of the global land surface are significantly correlated with at least 1 studied climatic mode. Among the 14 leading climatic modes, the El Ni no-Southern Oscillation(ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and Indian Ocean Dipole (IOD) affect terrestrial water storage in 76.5%, 74.6%, 59.7% and 46.4% of the global land surface, respectively. By associating each TC contribution, ENSO appears to have a weaker control on global land water storage than previously thought for dominating TWSA in 31.8% of global land, in contrast to PDO dominating TWSA in 36.6%. Our results suggest that the phase combination of TCs adjusts the response degree and time lag of land water storage via different hydrological cycle components, while the processes remain dynamic and highly uncertain.
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