Anomalous Features of Summer Cold Vortex over North China from 1999 to 2008
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Abstract:
Utilizing the monthly average temperature data of 160 stations, MICAPS data (two times per day) and NCEP 1°×1°data (four times per day) of May to August from 1999 to 2008, the conceptual model of severe convection associated with the cold vortex is devised, and the anomalies of the subtropical high pressure, East Asian monsoon, highaltitude jet, and lowlevel vertical motion are studied in the anomalous years of the cold vortex in summer. The results indicate that in the strong anomalous years of summer NCCVI (Nouth China Cold Vortex Index), there is a cyclonic circulation developed at 500 hPa over Lake Baikal, an upper trough from Lake Baikal to North China, and more active cold air; North China is affected by the southspreading steering flow after the trough. Various levels of the troposphere are warmer and wetter; the highaltitude jet in 200 hPa is stronger; the northerly air stream in the rear cold vortex at 700 hPa strengthens at high latitudes, and southerly air stream strengthens at low latitudes; the cold air and warm air converges in North China; ascending motion at lower levels develops over North China and North East. Over the same period, the subtropical high pressure is stronger and more southern; East Asian summer monsoon is stronger, which increases the transport of water vapor.In the weak anomalous years of summer NCCVI, these are on the contrary.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.