| 1. |
- Li, Y., et al.
(författare)
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Widespread spring phenology effects on drought recovery of Northern Hemisphere ecosystems
- 2023
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 13, s. 182-188
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Tidskriftsartikel (refereegranskat)abstract
- The authors reveal complex drought recovery responses to phenology shifts, in that early spring can shorten or lengthen recovery, while delayed spring following drought events delays it. These effects suggest a need to incorporate phenology aspects into resilience models. The time required for an ecosystem to recover from severe drought is a key component of ecological resilience. The phenology effects on drought recovery are, however, poorly understood. These effects centre on how phenology variations impact biophysical feedbacks, vegetation growth and, ultimately, recovery itself. Using multiple remotely sensed datasets, we found that more than half of ecosystems in mid- and high-latitudinal Northern Hemisphere failed to recover from extreme droughts within a single growing season. Earlier spring phenology in the drought year slowed drought recovery when extreme droughts occurred in mid-growing season. Delayed spring phenology in the subsequent year slowed drought recovery for all vegetation types (with importance of spring phenology ranging from 46% to 58%). The phenology effects on drought recovery were comparable to or larger than other well-known postdrought climatic factors. These results strongly suggest that the interactions between vegetation phenology and drought must be incorporated into Earth system models to accurately quantify ecosystem resilience.
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| 2. |
- Wang, L., et al.
(författare)
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Development of a land surface model with coupled snow and frozen soil physics
- 2017
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Ingår i: Water Resources Research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 53:6, s. 5085-5103
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Tidskriftsartikel (refereegranskat)abstract
- Snow and frozen soil are important factors that influence terrestrial water and energy balances through snowpack accumulation and melt and soil freeze-thaw. In this study, a new land surface model (LSM) with coupled snow and frozen soil physics was developed based on a hydrologically improved LSM (HydroSiB2). First, an energy-balance-based three-layer snow model was incorporated into HydroSiB2 (hereafter HydroSiB2-S) to provide an improved description of the internal processes of the snow pack. Second, a universal and simplified soil model was coupled with HydroSiB2-S to depict soil water freezing and thawing (hereafter HydroSiB2-SF). In order to avoid the instability caused by the uncertainty in estimating water phase changes, enthalpy was adopted as a prognostic variable instead of snow/soil temperature in the energy balance equation of the snow/frozen soil module. The newly developed models were then carefully evaluated at two typical sites of the Tibetan Plateau (TP) (one snow covered and the other snow free, both with underlying frozen soil). At the snow-covered site in northeastern TP (DY), HydroSiB2-SF demonstrated significant improvements over HydroSiB2-F (same as HydroSiB2-SF but using the original single-layer snow module of HydroSiB2), showing the importance of snow internal processes in three-layer snow parameterization. At the snow-free site in southwestern TP (Ngari), HydroSiB2-SF reasonably simulated soil water phase changes while HydroSiB2-S did not, indicating the crucial role of frozen soil parameterization in depicting the soil thermal and water dynamics. Finally, HydroSiB2-SF proved to be capable of simulating upward moisture fluxes toward the freezing front from the underlying soil layers in winter.
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| 3. |
- Zeng, Z. Z., et al.
(författare)
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A reversal in global terrestrial stilling and its implications for wind energy production
- 2019
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 9:12, s. 979-985
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Liang, E. Y., et al.
(författare)
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Strong link between large tropical volcanic eruptions and severe droughts prior to monsoon in the central Himalayas revealed by tree-ring records
- 2019
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Ingår i: Science Bulletin. - : Elsevier BV. - 2095-9273. ; 64:14, s. 1018-1023
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Tidskriftsartikel (refereegranskat)abstract
- Large tropical volcanic eruptions can cause short-term global cooling. However, little is known whether large tropical volcanic eruptions, like the one in Tambora/Indonesia in 1815, cause regional hydroclimatic anomalies. Using a tree-ring network of precisely dated Himalayan birch in the central Himalayas, we reconstructed variations in the regional pre-monsoon precipitation back to 1650 CE. A superposed epoch analysis indicates that the pre-monsoon regional droughts are associated with large tropical volcanic eruptions, appearing to have a strong influence on hydroclimatic conditions in the central Himalayas. In fact, the most severe drought since 1650 CE occurred after the Tambora eruption. These results suggest that dry conditions prior to monsoon in the central Himalayas were associated with explosive tropical volcanism. Prolonged La Nina events also correspond with persistent pre-monsoon droughts in the central Himalayas. Our results provide evidence that large tropical volcanic eruptions most likely induced severe droughts prior to monsoon in the central Himalayas. (C) 2019 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.
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| 5. |
- Park, C. E., et al.
(författare)
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Keeping global warming within 1.5 degrees C constrains emergence of aridification
- 2018
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Aridity-the ratio of atmospheric water supply (precipitation; P) to demand (potential evapotranspiration; PET)-is projected to decrease (that is, areas will become drier) as a consequence of anthropogenic climate change, exacerbating land degradation and desertification(1-6). However, the timing of significant aridification relative to natural variability-defined here as the time of emergence for aridification (ToEA)-is unknown, despite its importance in designing and implementing mitigation policies(7-10). Here we estimate ToEA from projections of 27 global climate models (GCMs) under representative concentration pathways (RCPs) RCP4.5 and RCP8.5, and in doing so, identify where emergence occurs before global mean warming reaches 1.5 degrees C and 2 degrees C above the pre-industrial level. On the basis of the ensemble median ToEA for each grid cell, aridification emerges over 32% (RCP4.5) and 24% (RCP8.5) of the total land surface before the ensemble median of global mean temperature change reaches 2 degrees C in each scenario. Moreover, ToEA is avoided in about two-thirds of the above regions if the maximum global warming level is limited to 1.5 degrees C. Early action for accomplishing the 1.5 degrees C temperature goal can therefore markedly reduce the likelihood that large regions will face substantial aridification and related impacts.
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| 6. |
- Yin, Y. Y., et al.
(författare)
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Quantifying Water Scarcity in Northern China Within the Context of Climatic and Societal Changes and South-to-North Water Diversion
- 2020
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Ingår i: Earths Future. - : American Geophysical Union (AGU). - 2328-4277. ; 8:8
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Tidskriftsartikel (refereegranskat)abstract
- With the increasing pressure from population growth and economic development, northern China (NC) faces a grand challenge of water scarcity, which can be further exacerbated by climatic and societal changes. The South-to-North Water Diversion (SNWD) project is designed to mitigate the water scarcity in NC. However, few studies have quantified the impact of the SNWD on water scarcity within the context of climatic and societal changes and its potential effects on economic and agricultural food in the region. We used water supply stress index (WaSSI) to quantify water scarcity within the context of environmental change in NC and developed a method to estimate the economic and agricultural impacts of the SNWD. Focuses were put on alleviating the water supply shortage and economic and agricultural benefits for the water-receiving NC. We find that societal changes, especially economic growth, are the major contributors to water scarcity in NC during 2009-2099. To completely mitigate the water scarcity of NC, at least an additional water supply of 13 billion m(3)/year (comparable to the annual diversion water by SNWD Central Route) will be necessary. Although SNWD alone cannot provide the full solution to NC's water shortage in next few decades, it can significantly alleviate the water supply stress in NC (particularly Beijing), considerably increasing the agricultural production (more than 115 Tcal/year) and bringing economic benefits (more than 51 billion RMB/year) through supplying industrial and domestic water use. Additionally, the transfer project could have impacts on the ecological environment in the exporting regions.
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