资源环境科技发展态势分析平台

Droughts can have devastating societal impacts. Yet, we do not fully understand the mechanisms that control their development, possibly affecting our ability to predict them. Here we run a moisture-tracking analytical model using reanalysis data between 1980 and 2016 to explore the role of reduced moisture transport in drought propagation. We find that agricultural droughts in multiple subregions across North America may be amplified by decreased moisture transport from upwind land areas, which we link to reduced evapotranspiration and dry soil moisture upwind. We also find that decreases in precipitation recycling are correlated with decreases in moisture arriving from upwind areas. We estimate that decreases in moisture contributions from land areas accounted for 62% of the precipitation deficit during the 2012 Midwest drought. Our results suggest that the land surface may contain useful information for drought prediction and highlight the importance of sustainable land use and of regional cooperation for drought risk management.

Plain Language Summary Droughts reduce the availability of water, which affects communities and ecosystems worldwide. Recent studies have shown that droughts may travel up to thousands of kilometers across continents, but it is still unclear what are the reasons behind these observed drought displacements. While there may be several reasons, we study one particular way in which droughts may be able to travel across continents. Our idea is that a drought in one area may decrease evaporation locally, which will reduce water vapor in the air. As the wind blows, it will transport drier air, which may lead to less precipitation downwind. We find links between droughts that take place in different regions across North America, suggesting that droughts may travel in this way, for example, from the U.S. Southwest to the U.S. Midwest. We also show that the lower evaporation that took place over the western United States, likely due to droughts in the region in 2012, increased the severity of the drought in the U.S. Midwest that year. Our study highlights the importance of sustainable land use management and the need for coordination between communities in upwind and downwind regions to reduce drought risks. It may also help improve future drought predictions.