Water vapor transport for spring persistent rains over southeastern China based on five reanalysis datasets

Abstract

In this study, atmospheric water vapor transport was analyzed to study the changes in spring persistent rainfall (SPR) over southeastern China from 1980 to 2012. The performances of five sets of reanalysis data in reproducing the climatology, the long-term trend and interannual variability of the SPR were synthetically evaluated. To understand the mechanisms dominating SPR variation, the major components of moisture budget, including vertical moisture advection, horizontal moisture advection and evaporation, were examined based on the five reanalysis datasets. The results show that all five reanalysis datasets reproduce the climatology of the SPR reasonably well. Strong westerly wind flow over the southern Tibetan Plateau and southwest wind flow over the western North Pacific are the two main channels remotely supplying water vapor for the SPR. Locally, moisture budget diagnosis shows that the SPR is primarily contributed by the evaporation and vertical moisture advection terms. The SPR shows a decreasing tendency [−0.38 mm day−1 (10 year)−1] during 1980–2012 along with strong interannual variation, which is reasonably captured by all five reanalysis datasets. Vertical moisture advection dominates the SPR variation, and the decreasing trend of the SPR is mainly due to the weakening of ascending motion during this period. In an El Niño decaying spring, the anomalous lower-tropospheric anticyclone over the western North Pacific intensifies vertical upward motion and leads to more precipitation. Both the Japanese 55-year reanalysis (JRA55) and the European Centre for Medium-Range Weather Forecast interim reanalysis (ERAIM) show higher skill in reproducing the climatology and changes of the SPR.