Role of land-atmosphere coupling in summer droughts and floods over eastern China for the 1998 and 1999 cases

Droughts and floods are the two most costly climate disasters over China. However, our ability to predict droughts and floods is limited by poor understanding of the atmospheric response to long memory climate drivers such as sea surface temperature and soil moisture. In this study, we investigate soil moisture feedbacks on summer droughts and floods over eastern China for the 1998 and 1999 cases using the Weather Research and Forecasting (WRF) model simulations. Soil moisture climatology, derived from a 20-year-long control run, is used to replace soil moisture evolution in uncoupled simulations for 1998 and 1999 summers. Eastern China experienced severe floods during the summer of 1998, while 1999 summer is characterized by a "southern flood and northern drought" pattern. The WRF model generally simulates relatively well the droughts and floods in the two summers. It is found that land-atmosphere coupling contributes substantially to both droughts and floods over northern China while it plays a relatively small role in precipitation anomalies over southern China. Our findings suggest that soil moisture memory help contribute skill to seasonal prediction of droughts and floods over northern China.