Diagnosing Potential Impacts of Tibetan Plateau Spring Soil Moisture Anomalies on Summer Precipitation and Floods in the Yangtze River Basin

Abstract

Soil moisture as a key variable of land processes greatly influences the weather and climate. This study investigates the observed linkage between Tibetan Plateau (TP) spring soil moisture and summer precipitation and floods in the Yangtze River basin during 1988–2008 using satellite and in‐situ observations. A significant (p = 1%) proportion of interannual variations of summer precipitation (about 25%) in the Yangtze River basin can be attributed to spring TP soil moisture anomalies which show a dipole pattern. When spring soil moisture anomalies are positive (negative) over eastern (western) TP, there is more summer precipitation and consequently river discharge in the Yangtze River basin, or vice versa. The possible mechanisms can be explained from the perspectives of surface energy balance and atmospheric thermodynamics. More (less) spring soil moisture over the eastern (western) plateau enhances summer diabatic heating, which may be related to soil moisture memory. The enhanced summer diabatic heating stimulates vigorous ascending motions over TP, which diverge in the upper troposphere (200 hPa) and descend over the western Pacific. This is conducive to the enhancement and mutual proximity of the South Asian High (SAH) and the Western Pacific Subtropical High (WPSH). As a result, the warm and humid air flows from the Bay of Bengal and the western Pacific and the cold and dry air flows from the boreal continent converge in the Yangtze River basin, causing excessive summer precipitation. Therefore, TP spring soil moisture can be considered a seasonal predictor of summer precipitation and possible subsequent floods in the Yangtze River basin.

Preference of Afternoon Precipitation Over Dry Soil in the North China Plain During Warm Seasons

“…Most of the studies related to the effect of SM on precipitation (SM‐P) in China are concerned with large‐scale coupling, usually associated with non‐local effects and long timescale effects (Fan et al., 2019; Liang & Chen, 2010; Ma et al., 2000; Zuo & Zhang, 2007). For example, positive spring SM anomalies over the eastern Tibetan Plateau (TP) lead to more precipitation in the Yangtze River basin (Zhu et al., 2023). There is a positive (negative) correlation between spring SM over the northeastern TP and summer precipitation over North (South) China (Li & Wang, 2016).…”

Long-Term Characteristics of Surface Soil Moisture over the Tibetan Plateau and Its Response to Climate Change

“…It is urgent to fully understand the responses of the water cycle to climate change over the TP and its underlying mechanism. As one of the main hydrological components, TP soil moisture can not only affect local land-atmosphere interactions through surface energy partitioning [16], but also remotely affect weather and climate through large-scale atmospheric circulations [17,18].…”