Variation in Summer Rainfall in North China during the Period 1956--2007 and Links with Atmospheric Circulation |
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| Authors: | LIANG Feng TAO Shiyan WEI Jie and BUEH Cholaw |
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| Institution: | Beijing Meteorological Bureau, China Meteorological Administration, Beijing 100089, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,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: | Using gauge precipitation data and NCEP--NCAR reanalysis data, the
interdecadal changes in summer precipitation during the period 1956--2007 in
North China and the link with atmospheric circulation change over Eurasia
are studied. Results show that precipitation amounts decreased by 16.2 mm
per decade, which was attributable to a significant reduction in
precipitation frequency. Contrary wave trains were found in the subtropical
westerly jet (wave guide) over Eurasia for the wet and dry years of North
China. When the wave trains had a ridge (trough) around the Korean
Peninsula, conditions favored (disfavored) the westward and northward
extension of the West Pacific subtropical high. The westward and northward
extension of the West Pacific subtropical high is, and was, beneficial to
rainfall in North China. The downstream propagation of Rossby waves was
found to favor the maintenance of these wave trains. Sensible heating in the
south of Lake Baikal and latent heating from the Korean Peninsula to the
south of Japan increased during the period 1980--2007, as compared to that
during 1957--1979, the wet period. These changes had positive influences on
the maintenance of Anticyclonic-Cyclonic anomaly centers in the wave trains.
Furthermore, northerly winds were prevalent in the lower troposphere during
the dry period (1980--2007), which prohibited the transportation of water
vapor to North China from the seas and thereby led to a decrease in rainfall
in North China. The weakening of the Indian Monsoon during the dry period
might be one of reasons for the reduction in water vapor transportation. |
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| Keywords: | North China precipitation frequency wave trains downstream development water vapor transportation latent heat sensible heat |
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