NUMERICAL SIMULATION OF THE IMPACT OF LATENT HEAT FLUX ANOMALY IN THE TROPICAL WESTERN PACIFIC ON PRECIPITATION OVER SOUTH CHINA IN JUNES

Based on composite analysis and numerical simulations using a regional climate model (RegCM3), this paper analyzed the impact of the LHF anomaly in the tropical western Pacific on the precipitation over the south of China in June. The results are as follows. (1) Correlation analysis shows that the SC precipitation in June is negatively correlated with the LHF of the tropical western Pacific in May and June, especially in May. The SC precipitation in June appears to negatively correlate with low-level relative vorticity in the abnormal area of LHF in the tropical western Pacific. (2) The LHF anomaly in the tropical western Pacific is a vital factor affecting the flood and drought of SC in June. A conceptual model goes like this: When the LHF in the tropical western Pacific is abnormally increased (decreased), an anomalous cyclone (anticyclone) circulation is formed at the low-level troposphere to its northwest. As a result, an anomalous northeast (southwest) air flow affects the south of China, being disadvantageous (advantageous) to the transportation of water vapor to the region. Meanwhile, there is an anomalous anticyclone (cyclone) at the low-level troposphere and an anomalous cyclone (anticyclone) circulation at the high-level troposphere in the region, which is advantageous for downdraft (updraft) there. Therefore a virtual circulation forms updraft (downdraft) in the anomalous area of LHF and downdraft (updraft) in the south of China, which finally leads to the drought (flood) in the region;