The Variation Characteristics Of Mascarene High And Its Relationship With The Summer Precipitation In Eastern China

Using the NCEP/NCAR reanalyzed data and the monthly rainfall data at 160stations in China, we analyze the variation characteristic of Mascarene high (MH)and its correlation on summer precipitation in eastern China. The results show that:1) The seasonal characteristics of Mascarene high are obvious in the spatialstructure. From January. to July, MH's intensity is increased with a morenorthwestward position; from July to next January, MH's intensity is decreased witha southeastward position.Nearly 50 years, four seasonal indexes of MH have ascending trends and havean abrupt change at the late of 1970's. The indexes are in negative phase before thelate 1970's and positive phase after that time.2) Results show that MH in April impacts on precipitation in eastern China insummer most. For Mascarene High in April, there is a strong negative correlationwith rainfall in south China in June, positive correlation with the rainfall in themiddle and lower reaches of the Yangtze River from June to July and negativecorrelation with rainfall in north China from July to August.3) When MH in April is strong (weak), MH in summer also becomes strong (weak)because of the continuance and Somalia jet increase (decrease). Meanwhile most ofAsia has positive (negative) anomalies in spring at the lower troposphere level andthe anomalies continue strengthening from spring to summer which extend to theMongolian Plateau region. In the summer, there is a north (south) airflow in the eastof Asia which results in East Asian monsoon weakening (strengthening). At thesame time, the Western Pacific subtropical high trends to be a more southwestward(northeastward) position. All of the above result in rain bands southward (northward),more (less) rainfall in the middle and lower reaches of the YangtzeRiver and less (more) rainfall in north China..The results show that MH's indexes in April can provide a preliminary, sign forthe precipitation forecast of the middle and lower reaches of the Yangtze River andnorth China.