Dominance of climate warming effects on recent drying trends over wet monsoon regions

Abstract. Understanding changes in continental surface dryness is key information for adapting to climate change because of the critical socioeconomic consequences. Recent studies reveal that spatial patterns of continental dryness trends are in contrast to the "dry gets drier, wet gets wetter" paradigm. Causes of the complexity in dryness trends remain uncertain because various climate parameters control continental dryness. Here, we quantify the relative effects of dominant climate drivers on dryness trends over continental East Asia, which is characterized by diverse hydro-climate regimes ranging from humid to arid, by analyzing observed data from 189 weather stations for the period of 1961–2010. Since the early 1980s, monsoon climate zones (east of 100° E) have been getting significantly drier, but the related mechanisms vary according to the hydro-climate regime. Drying trends in arid regions are mostly explained by reduced precipitation. In contrast, in humid areas, the increase in evapotranspiration due to increased atmospheric water-holding capacity, a secondary impact of warming, is the primary condition for the increase in dryness. This drying impact of atmospheric moisture deficiency is much stronger in humid areas than in arid areas. Our results suggest that enhanced atmospheric water demands caused by warming can threaten water resources in wet monsoon areas and possibly in other warm and water-sufficient regions.