A quantitative diagnosis for persistent heavy rain in Jiangxi in June 2010

Using operational observation data and National Centers for Environmental Prediction (NCEP) Final operational (FNL) analysis data, a quantitative diagnosis is carried out for the upward branch of a local meridional circulation over Jiangxi during 0200 17 to 1400 18 May (first stage) and 0800 19 to 2000 20 May (second stage). The results show that the upward motion is mainly associated with latent heating in both the two stages. The stimulated omega is large in second stage (-0.353 Pa·s^-1) than first stage (-0.212) Pa·s^-1. The meridional temperature advection, the meridional westerly momentum advection and the boundary conditions have positive contributions, while the vertical transportation of mean temperature and the zonal westerly momentum advection have negative contributions to upward motion in first stage. In addition to the meridional temperature advection, the meridional westerly momentum advection and the boundary conditions, the mean temperature vertical transportation and the zonal westerly momentum advection have turned positive contributions to upward motion in second stage. The corresponding analyses indicate the following results. (1) The 500 hPa shallow rough over southeast Tibetan Plateau moving eastward and deepening, merging to a cut-off low which moved southeastward are the main causes of the upward movement stimulated by the latent heating enhanced in the second stage. (2) The convergence sinking (divergence pumping) of the upper westerly jet exit(entrance) anticyclone shear side is the main reason for positive (negative) contribution of mean westerly momentum zonal advection in the first (second) stage. (3) The upward (downward) transportation of the mean temperature is the main reason for negative (positive) contribution in the first(second) stage. (4) The warm advection is main reason for the positive contribution in two rainfall stages.