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Proceedings Paper

Orographic effects on South China Sea summer climate
Author(s): Haiming Xu; Shang-Ping Xie; Yuqing Wang; Wei Zhuang; Dongxiao Wang
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Paper Abstract

New satellite observations reveal several distinct features of the South China Sea (SCS) summer climate: an intense low-level southwesterly wind jet off the coast of south Vietnam, a precipitation band on the western flank of the north-south running Annam mountain range, and a rainfall shadow to the east in the western SCS off the east coast of Vietnam. A high-resolution full-physics regional atmospheric model is used to investigate the mechanism for the formation of SCS summer climate. A comparison of the control model simulation with a sensitivity experiment with the mountain range artificially removed demonstrates that the aforementioned features form due to orographic effects of the Annam mountains. Under the prevailing southwesterly monsoon, the mountain range forces the ascending motion on the windward and subsidence on the lee side, giving rise to bands of active and suppressed convection, respectively. On the south edge of the mountain range, the southwesterlies are accelerated to form an offshore low-level wind jet. The mid-summer cooling in the SCS induced by this wind jet further helps reduce precipitation over the central SCS. A reduced-gravity ocean model is used to investigate the ocean response to the orographically induced wind forcing, which is found to be important for the formation of the double-gyre circulation observed in the summer in SCS, in particular for the northern cyclonic circulation. Thus, orography is a key to shaping the SCS summer climate both in the atmosphere and in the ocean.

Paper Details

Date Published: 13 September 2007
PDF: 12 pages
Proc. SPIE 6685, Assimilation of Remote Sensing and In Situ Data in Modern Numerical Weather and Environmental Prediction Models, 66850K (13 September 2007); doi: 10.1117/12.730375
Show Author Affiliations
Haiming Xu, Nanjing Univ. of Information Science & Technology (China)
Shang-Ping Xie, Univ. of Hawaii (United States)
Yuqing Wang, Univ. of Hawaii (United States)
Wei Zhuang, South China Sea Institute of Oceanology (China)
Dongxiao Wang, South China Sea Institute of Oceanology (China)

Published in SPIE Proceedings Vol. 6685:
Assimilation of Remote Sensing and In Situ Data in Modern Numerical Weather and Environmental Prediction Models
Xiaolei Zou; Dale Barker; Francois-Xavier Le Dimet, Editor(s)

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