Characteristics Of Summer Water Vapor Transport In The Eastern Northwest China And Their Relationship With Precipitation

In this paper,ERA Interim reanalysis data and monthly precipitation observation station data from 160 stations in Summer(JJA) over the eastern Northwest of China(ENC) for the period 1979-2013 are used and the statistical methods are adopted .The main results are as follows :In May,it is the features of change of transport pattern from summer to winter.With the Asian summer monsoon onsets, the water vapor transport over the tropical Indian Ocean and the Bay of Bengal greatly intensifies.The water vapor transport from ground to upper atmosphere obviously are varying with monthly.It is the features of change of transport pattern from winter to summer.The moisture budgets are well related to the precipitation in summer in the ENC.In the eastern border,it has significant effect by northward subtropical high in June to July. In the west boundry, it is greatly influenced by the terrain.In the south,the influence of Asian monsoon in ENC is significant.In the north corridor,it is hardly change.The EOF analysis of the moisture transport showed that,the first EOF distribution pattern of the vapor flux depicts the consistent eastward transport anomaly . It increases from south to north boundary.EOF2 basically reflected the characteristics of north transport.There are three leading modes in the spatio-temporal variations of summertime precipitation anomalies over the ENC.The first leading mode there are positive in ENC.Precipitation is decrease from south to north.The anticyclonic anomaly lies in the southeast of China and the cyclonic anomaly lies in the Baikal-Intense southwesterly water vapor transport prevails in ENC in summer.The second leading mode,the distribution of summertime precipitation anomalies depict southeast-northwest pattern in ENC,exhibited a "+-+"meridional tripole pattern from south to north.The vapor mainly comes from latitudinal transport governed by easterly and longitudinal transport dominated by northeast current.The third leading mode , it displays a southwest-northeast pattern.An anomalous low-pressure is established over the north of China.The ENC stands behind of the middle and high latitude trough.Intense westerly wind prevails in ENC.The results of composite analysis indicate that the more rain had the characteristics of a positive-negative-positive anomalous distribution from west to eastin high latitudes from Europe to Asia. Location of the western Pacific subtropical high was to the north and west as compared with the normal.In 850hPa wind field,show that an anomalous low-pressure is established over the east of Baikal and an anomalous anti-cyclonic circulation is established over the East China Sea.