Intensification and expansion of soil moisture drying in warm season over Eurasia under global warming
Xihui Gu1,5,11, Qiang Zhang2,3,4*, Jianfeng Li5*, Vijay P. Singh6, Jianyu Liu7, Peng Sun8, Chunyang He9,10, Jianjun Wu2,3,4
Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China;
Key Laboratory of Environmental Change and Natural Disaster, Ministry of Education, Beijing Normal University, Beijing 100875, China;
Faculty of Geographical Science, Academy of Disaster Reduction and Emergency Management, Beijing Normal University, Beijing 100875, China;
State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China;
Department of Geography, Hong Kong Baptist University, Hong Kong, China;
Department of Biological & Agricultural Engineering and Department of Civil and Environmental Engineering, Texas A & M University, College Station, Texas 77843-2117, USA;
Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;
School of Geography and Tourism, Anhui Normal University, Wuhu 241002, China;
9. Center for Human-Environment System Sustainability (CHESS), State Key Laboratory of Earth Surface Processes and Resource Ecology (ESPRE), Beijing Normal University, Beijing, China;
10. School of Natural Resources, Faculty of Geographical Science, Beijing Normal University, Beijing, China;
11. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS, China.
Abstract: Soil moisture (SM) is a key hydrological component regulating the net ecosystem energy exchange at the land-atmosphere boundary layer over the continents via heat fluxes and relevant feedback on precipitation. Due to its ecological and meteor-hydrological implications, SM change is of great significance in Eurasia which has the highest population density and fragile ecological environment. Using monthly data from the Global Land Data Assimilation System (GLDAS), this study investigated SM changes over Eurasia during the warm season (May-September). It was found that recent 63 years witnessed widespread decreasing SM across Eurasia during the warm season. Regions with a drying SM tendency kept expanding till the 1990s. Specifically, the largest decreasing magnitude of SM with the Aridity Index (AI) ranging 0.5-0.6 and 1.0-1.1 was found along the semi-arid and dry-humid transition regions, respectively. In addition, more significant drying SM was observed in Sahel, northern Asia, northeastern Asia, and Western Europe. Weakening West African monsoon (WAM)/East Asia summer monsoon (EASM) did not benefit the propagation of water vapor flux to the Sahel regions/northeastern and northern Asia, and hence decreased SM in these regions. Besides, results by the Maximum Covariance Analysis (MCA) highlighted the roles of warming climate in SM variations over Eurasia during the warm season. Global Climate Models (GCMs) also indicate decreased SM due to global warming and projects continuously decreasing SM in the warm season over the 21st century under RCP2.6, RCP4.5, RCP6.0, and RCP8.5 scenarios. Decreasing SM across the Eurasia and related ecological and environmental implications should cause international concern.
Published in Journal of Geophysical Research Atmospheres, DOI:10.1029/2018JD029776, 2019
