Analysis Of Water-vapor Transport And Related Circulation Anomalies Before Persistent Heavy Rainfall Events Over Southeast Coastal Area

Based on the NCEP/NCAR reanalysis data,16 cases of Persistent Heavy Rain events(PHR)over Southeast Coastal Area during 1951-2010 are selected to study the mechanism of PHR,associated with water vapor transport and related circulation anomalies.The HYSPLIT model is used to simulate the trajectories of air particles,also associated the vapor fluxes to analyze the characteristics of water vapor transport and related circulation backgrounds.Based on these results,confirm the critical circulation systems which are important for the establishment and maintenance of water vapor transport.At the same time,according to the results of correlation analysis,identify the circulation anomalies which are important for the PHR process.Then combined with the method of weather analysis,the mechanism of circulation anomalies on critical circulation systems are preliminary revealed.The results show the water vapor mainly comes from Indian Ocean,the South China Sea and Northwest Pacific during the process.There are 5 passages:the Arabian passage,the Somali passage,the Bay of Bengal passage,the South China Sea passage and western Pacific passage.The abnormal water vapor from the Bay of Bengal and Western Pacific play an important role for the occurrence and maintenance of PHR process.They convergence in South China Sea and transport northward to Southeast Coastal Area.Western Pacific Subtropic High,Indian Monsoon Depression and several cross equatorial flow are systems that have a significant impact on the establishment and maintenance of water vapor transport.The intensity,location and morphological evolution of these systems are effected by the circulation anomalies from different regions.The main mechanisms include the interaction of the northern and southern hemispheres,the adjustment of large-scale circulation,and so on.