Interannual variability of the evaporation duct over the South China Sea and its relations with regional evaporation

The interannual variability of the evaporation duct over the South China Sea is investigated during the boreal winter and summer seasons using data sets from the National Centers for Environment Prediction Climate Forecast System Reanalysis. During winter, the distribution is characterized by a tripole-like structure, whereas in summer the pattern exhibits a west-east contrast. Special attention is paid to the links of the evaporation duct with the regional evaporation by analyzing the leading empirical orthogonal functions of both elements. Both the structural similarity in spatial patterns and the significant correlation in the principal components imply the inherent relevance between evaporation duct and evaporation. During both the winter and summer seasons, the empirical orthogonal function principal component 1 of the evaporation duct and evaporation are linked significantly with the regional atmospheric dynamics, the primary factor dominating the whole South China Sea. The partial correlation analysis reveals that, similar to the evaporation process, surface wind is a more important factor affecting evaporation duct than sea surface temperature. The results also indicate that the influence of surface wind and SST not only has an obvious seasonal dependence, but also displays a prominent south-north contrast.