Anomalous Midsummer Rainfall in Yangtze River-Huaihe River Valleys and Its Association with the East Asia Westerly Jet |
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| Authors: | XUAN Shouli ZHANG Qingyun and SUN Shuqing |
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| Institution: | Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, Graduate University of Chinese Academy of Sciences, Beijing 100049,Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | In this study, the interannual and interdecadal relationship between midsummer Yangtze River-Huaihe River valley (YHRV) rainfall
and the position of the East Asia westerly jet (EAWJ) were investigated. The midsummer YHRV rainfall was found to significantly
increase after the 1980s. Moreover, the location of the EAWJ was found abnormally south of the climatic mean during 1980–2008
(ID2) compared to 1951–1979 (ID1). During ID2, associated with the southward movement of the EAWJ, an anomalous upper-level
convergence occurred over middle-high latitudes (35°-55°N) and divergence occurred over lower latitudes (～30°N) of East Asia.
Correspondingly, anomalous descending and ascending motion was observed in middle-high and lower latitudes along 90°–130°E,
respectively, favoring more precipitation over YHRV. On an interannual time scale, the EAWJ and YHRV rainfall exhibited similar
relationships during the two periods. When the EAWJ was centered abnormally southward, rainfall over YHRV tended to increase.
However, EAWJrelated circulations were significantly different during the two periods. During ID1, the circulation of the
southward-moving EAWJ exhibited alternating positive-negative-positive distributions from low to middle-high latitudes along
the East Asian coast; the most significant anomaly appeared west of the Okhotsk Sea. However, during ID2 the EAWJ was more
closely correlated with the tropical and subtropical circulations. Significant differences between ID1 and ID2 were also recorded
sea surface temperatures (SSTs). During ID1, the EAWJ was influenced by the extratropical SST over the northern Pacific; however,
the EAWJ was more significantly affected by the SST of the tropical western Pacific during ID2. |
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| Keywords: | anomalous rainfall events Yangtze River-Huaihe River valleys East Asian westerly jet wave activity |
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