Regional disparities in warm season rainfall changes over arid eastern–central Asia

Abstract

Multiple studies have reported a shift in the trend of warm season rainfall over arid eastern–central Asia (AECA) around the turn of the new century, from increasing over the second half of the twentieth century to decreasing during the early years of the twenty-first. Here, a closer look based on multiple precipitation datasets reveals important regional disparities in these changes. Warm-season rainfall increased over both basin areas and mountain ranges during 1961–1998 due to enhanced moisture flux convergence associated with changes in the large-scale circulation and increases in atmospheric moisture content. Despite a significant decrease in warm-season precipitation over the high mountain ranges after the year 1998, warm season rainfall has remained large over low-lying basin areas. This discrepancy, which is also reflected in changes in river flow, soil moisture, and vegetation, primarily results from disparate responses to enhanced warming in the mountain and basin areas of AECA. In addition to changes in the prevailing circulation and moisture transport patterns, the decrease in precipitation over the mountains has occurred mainly because increases in local water vapor saturation capacity (which scales with temperature) have outpaced the available moisture supply, reducing relative humidity and suppressing precipitation. By contrast, rainfall over basin areas has been maintained by accelerated moisture recycling driven by rapid glacier retreat, snow melt, and irrigation expansion. This trend is unsustainable and is likely to reverse as these cryospheric buffers disappear, with potentially catastrophic implications for local agriculture and ecology.

East Asian Study of Tropospheric Aerosols and their Impact on Regional Clouds, Precipitation, and Climate (EAST‐AIRCPC)

“…This ACI effect leads to suppression of shallow liquid clouds and invigoration of warm-base mixed-phase clouds. The orography effect on precipitation cannot be ignored either (e.g., Dong et al, 2018;Fan et al, 2015;Guo, Deng, et al, 2014). In addition to changes in the prevailing circulation and moisture transport patterns, a decrease in precipitation over mountains has occurred mainly because increases in the local water vapor saturation capacity, which scales with temperature, have outpaced the available moisture supply.…”

“…In addition to changes in the prevailing circulation and moisture transport patterns, a decrease in precipitation over mountains has occurred mainly because increases in the local water vapor saturation capacity, which scales with temperature, have outpaced the available moisture supply. This reduces the relative humidity, suppressing precipitation (Dong et al, 2018). The coupling effect of aerosols and orographic lifting has proven to be crucial for precipitation forecasts (Fan et al, 2015;Rosenfeld et al, 2007).…”

Towards understanding the pattern of glacier mass balances in High Mountain Asia using regional climatic modelling

“…Yonsei University (YSU) scheme (Hong et al, 2006) Atmospheric surface layer MM5 Monin-Obukhov scheme (Beljaars, 1995;Dyer and Hicks, 1970;Paulson, 1970;Webb, 1970;Zhang and Anthes, 1982) Land surface Noah-MP (Niu et al, 2011)…”

Detecting human influence on the temperature changes in Central Asia

“…Meanwhile, the precipitation in Central Asia shows significant increasing trend during the past five decades, with the largest increasing trend in Northwest China (Shi et al 2007;Chen et al 2011;Zhao et al 2014;Li et al 2016;Hu et al 2017). Consequently, results from rain gauge observations indicate that the climate over Northwest China shifts from warm and dry to warm and wet (Shi et al 2007;Li et al 2015Li et al , 2016Li et al , 2017bDong et al 2018;Rodell et al 2018).…”