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A summer weather index in the East Asian pressure field and associated atmospheric circulation and rainfall
Author(s) -
Zhao Ping,
Zhu Yani,
Zhang Qin
Publication year - 2010
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.2276
Subject(s) - subtropical ridge , climatology , atmospheric circulation , environmental science , east asia , ridge , precipitation , monsoon , china , geography , geology , meteorology , cartography , archaeology
Using the daily rainfall from rain gauge stations in China and the daily data from the National Centers for Environmental Prediction‐National Center for Atmospheric Research (NCEP‐NCAR) reanalysis for each year of 1981–2008, a relationship between daily rainfall over the Yangtze‐Huaihe River basin (YHB) and surface pressure over East Asia was statistically investigated and a summer weather index ( I SW ) was defined from surface pressure for describing the daily variations of the atmospheric circulation and rainfall over the monsoon region of eastern China. The results show that the daily I SW is significantly correlated with the YHB rainy weather during summer. In higher‐ I SW days, there is usually more YHB rainfall. This link may be explained by the East Asian atmospheric circulation well. When I SW is higher, a low‐pressure system frequently occurs over the land of southern China and an enhanced ridge appears over the South China Sea (SCS)–subtropical western Pacific region, which strengthens the seaward pressure gradient and southwesterly winds over southern China. Accordingly, the transport of water vapour toward the YHB and the ascending motion over the YHB strengthen remarkably. These variations in the daily atmospheric circulation finally lead to the frequent occurrence of the YHB rainy weather. Thus, I SW can represent the variations of the atmospheric circulation and rainy weather for most of the years of 1981–2008. For some extremely dry years over the YHB, however, I SW does not indicate the local large‐scale rainfall well. This suggests an asymmetric descriptive ability of this index. Copyright © 2010 Royal Meteorological Society