Structural variation of an atmospheric heat source over the Qinghai-Xizang Plateau and its influence on precipitation in northwest China |
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Authors: | Na Wei Yuanfa Gong Jinhai He |
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Affiliation: | Shaanxi Provincial Climate Center, Xi'an 710015, Center for Plateau Atmospheric and Environmental Research, Department of Atmospheric Science, Chengdu University of Information Technology, Chengdu 610225,,Center for Plateau Atmospheric and Environmental Research, Department of Atmospheric Science, Chengdu University of Information Technology, Chengdu 610225, College of Atmosphere Sciences, Nanjing University of Information Science and Technology, Nanjing 210044,College of Atmosphere Sciences, Nanjing University of Information Science and Technology, Nanjing 210044 |
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Abstract: | NCEP/NCAR reanalysis data and a 47-year precipitation dataset are utilized to analyze the
relationship between an atmospheric heat source (hereafter called < Q1 >) over the Qinghai-Xizang
Plateau (QXP) and its surrounding area and precipitation in northwest China. Our main conclusions
are as follows: (1) The horizontal distribution of < Q1 > and its changing trend are dramatic over
QXP in the summer. There are three strong centers of < Q1 > over the south side of QXP with obvious
differences in the amount of yearly precipitation and the number of heat sinks predominate in the
arid and semi-arid regions of northwest China (NWC), beside the northern QXP with an obvious higher
intensity in years with less precipitation. (2) In the summer, the variation of the heat source's
vertical structure is obviously different between greater and lesser precipitation years in eastern
northwest China (ENWC). The narrow heat sink belt forms between the northeast QXP and the southwestern
part of Lake Baikal. In July and August of greater precipitation years, the heating center of the
eastern QXP stays nearly over 35oN, and at 400 hPa of the eastern QXP, the strong upward motion of
the heating center constructs a closed secondary vertical circulation cell over the northeast QXP
(40o--46oN), which is propitious to add precipitation over the ENWC. Otherwise, the heating
center shifts to the south of 30oN and disappears in July and August of lesser precipitation years,
an opposite secondary circulation cell forms over the northeast QXP, which is a disadvantage for
precipitation. Meanwhile, the secondary circulation cell in years with more or less precipitation
over the ENWC is also related to the heat source over the Lake Baikal. (3) The vertical structure of
the heat source over the western QXP has obvious differences between greater and lesser precipitation
years in western northwest China in June and July. The strong/weak heat source over the western QXP
produces relatively strong/weak ascending motion and correspondingly constructs a secondary circulation
cell in lesser/greater precipitation years. |
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Keywords: | Qinghai-Xizang Plateau atmospheric heat source/sink greater/lesser precipitation years northwest China |
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