Mechanistic Analysis of the Influence of the Latent Heat Associated with the Kuroshio Current on Chinese Rainfall Anomalies in Spring

Using NCEP/NCAR reanalysis data, Hadley Centre SST data, station precipitation data, and Objectively Analyzed Air-sea Fluxes (OAFlux) latent and sensible heat flux data, the impacts of Kuroshio Current latent heat flux on Chinese precipitation anomalies in spring during 1960-2010 are investigated. Firstly, the results of air-sea interaction in the Kuroshio region indicate a forcing of the atmosphere to the ocean in the summer, and a forcing of the ocean to the atmosphere in the winter and spring. There is no clear signal for the air-sea interaction in the autumn. In spring, the sensible heat and latent heat fluxes in the Northwest Pacific are sensitive to the Kuroshio Current, and the maximum of both the sensible and latent heat appears in the region of the Kuroshio Current. The climate mean sensible and latent heat fluxes in the Kuroshio Current area are 30 and 120 W m^-2, respectively. Large standard deviation values of latent heat flux in spring are mainly distributed in the East China Sea and to the southeast of Japan, which is the Kuroshio Current region. However, large standard deviation values of sensible heat flux are mainly distributed to the west of Japan. The spatial pattern of the first EOF mode for the latent heat flux in the East China Sea and surrounding areas shows a large-value area located just inside the Kuroshio Current region. Further linear correlation analysis and composite studies confirm that the spring rainfall is above normal in South China and below normal in central China when the Kuroshio Current Latent Index (KLI) is larger than 0.8. The atmospheric circulation associated with the KLI indicates a significant change in the wind anomaly over China. When the KLI is larger than 0.8, northerly wind anomalies occur over China. The southwesterly wind in the northwest of the subtropical high is mainly distributed in southern China. Hence, water vapor cannot be transported northward, resulting in accumulation of water vapor in southern China. In this case, more rainfall is observed in southern China and less rainfall in central China. The situation is roughly the opposite when the KLI is smaller than -0.8.