The sources and transportation of water vapor in persistent heavy rainfall events in the Yangtze-Huaihe River Valley

The HYSPLIT model and NCEP/NCAR reanalysis data were used to analyze the sources and transportation of water vapor and dry air during periods of persistent heavy rainfall events (PHREs) over the Yangtze-Huaihe River Valley (YHRV). Main results are as follows. There are two dry air invasion paths during PHREs to the south of the YHRV. One is the northwesterly path from Mediterranean-European plain, and the other one is northeasterly path from Mongolia plateau. But during PHREs in the north of the YHRV, the dry air invasion path is mainly from the northwesterly path. Dry air is transported to the YHRV through the activities of trough, ridge and jet on the middle-upper troposphere. There are two moisture transportation paths in PHREs to the south of the YHRV. One is the southwesterly path originating from the tropical India Ocean, and the other one is the southerly path originating from Indonesia and the South China Sea. There are three moisture transportation paths during PHREs to the north of the YHRV. Two paths out of the three are similar to those to the south of YHRV during PHREs, and are the major water vapor transport paths. The third path is the southeasterly path from the western Pacific Ocean. During the PHREs of YHRV, the water vapor transport is controlled by the Somali cross-equatorial jet and cross-equatorial flow near the Bay of Bengal and Indonesian archipelago, and affected by the western Pacific subtropical high pressure.