Diagnostic Study of Summer Moisture Sinks over the Yangtze-Huaihe River Basin in 2011 Based on High-Resolution ERA-Interim Reanalysis Data

The summer moisture sink and its components in the Yangtze-Huaihe River basin (YHRB) in 2011 were investigated using high-resolution ERA-Interim reanalysis data at a horizontal resolution of approximately 0.7°×0.7° with 60 σ vertical levels. The associated large-scale general circulation and synoptic disturbances were also investigated. The results can be summarized as follows. 1) Summer water vapors over the YHRB are well matched based on the water vapor balance equations used for the ERA-Interim data. The moisture sink derived from water vapor convergence minus the local moisture tendency is highly consistent with its counterpart derived from precipitation minus evaporation (P-E), indicating good performance of the ERA-Interim reanalysis in describing moisture sinks for the YHRB region. 2) On a monthly mean basis, the YHRB area was a moisture sink in summer 2011, and its evolution exhibits a pronounced 2-6-day synoptic fluctuation. The contribution of precipitation to the moisture sink is notably larger than that of evaporation during the rainy season. Conversely, both moisture convergence and the local moisture tendency play an important role in the moisture sink, with a 1-2-day predictable skill for its daily change. 3) Combined with water vapor transport associated with moisture convergence, both the large-scale circulation and local synoptic weather systems contribute greatly to the YHRB regional moisture sink. In particular, the position of the western Pacific subtropical high is closely related to the regional moisture sink on a monthly mean basis, whereas local weather disturbances over the YHRB and southwestern China primarily impact the regional moisture sink on a synoptic basis.