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

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. Plain Language Summary: Spring soil moisture over the Tibetan Plateau (TP) explains a significant proportion of interannual variations of summer precipitation (about 25%) in the Yangtze River basin. When spring soil moisture anomalies are positive (negative) over the 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 attributed to the perspectives of surface energy balance and atmospheric thermodynamics. More (less) spring soil moisture over the eastern (western) plateau enhances summer diabatic heating. The diabatic heating controls the atmospheric circulation changes over the TP and surrounding regions associated with the enhancement and eastward (westward) stretching of the South Asian High (Western Pacific Subtropical High), favoring the convergence of the warm and humid (cold and dry) air flows from Tropical Ocean (boreal continent) to the Yangtze River basin, resulting in excessive summer precipitation. Key Points: Spring soil moisture over the Tibetan Plateau (TP) explains about 25% of interannual variations of summer precipitation in the Yangtze River basinPositive (negative) soil moisture anomalies over eastern (western) TP lead to more precipitation and discharge in the Yangtze River basinMore precipitation is due to moisture‐rich airflow convergence linked to South Asian High and Western Pacific Subtropical High affected by soil moisture‐induced diabatic heating [ABSTRACT FROM AUTHOR]