Annual cycle of rainfall in the western North Pacific and East Asian sector

Chia Chou, Li Fan Huang, Lishan Tseng, Jien Yi Tu, Pei Hua Tan

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The annual cycle of precipitation over the western North Pacific and East Asian (WNP-EA) sector has five major periods: spring, the first and second wet periods, fall, and winter. In this study, processes that induce precipitation in each period are examined from a large-scale point of view. The wet phase over this sector has two distinct periods,which are dominated by theAsian summermonsoon circulation induced by the land-ocean contrast of net energy into the atmospheric column (Fnet). In the first wet period, the pre-mei-yu/mei-yu rainband is directly associated with a moisture flux convergence caused by the southwesterly Asian summer monsoon flow and the southeasterly trade winds, and indirectly associated with a dynamic feedback induced by this horizontal moisture convergence. The tropical convection, in the meantime, is associated with a rising motion that is induced by positive Fnet. In the second wet period, the WNP summer monsoon gyre dominates the rainfall of this region, which is partially associated with warmer local sea surface temperature (SST) via positive Fnet. The land-sea contrast of Fnet and the atmosphere-ocean interaction also play an important role in establishing the monsoon gyre. The dry phase over the WNP-EA region is the winter period in which precipitation is associated with winter stormactivities and large-scale lifting associated with a pressure surge. In the two transition phases, due to a difference in heat capacity, the atmosphere and ocean have distinct impacts on precipitation, albeit similar solar insolations during the two periods. In the spring period, the atmospheric condition is favorable for convection, while the ocean surface is relatively colder, so the horizontal moisture advection associated with the westward extent of the Pacific subtropical high, which is different from a typical winter frontal system, is a major source for the spring rain. In the fall period, however, the atmospheric conditions dominated by the Asian winter monsoon circulation suppress convection, while relatively warmer SST stillmaintains tropical convection over the southern part of theWNP-EAregion.Over the northern part of the WNP-EA region, the fall precipitation is associated with frontal systems, similar to those in winter.

Original languageEnglish
Pages (from-to)2073-2094
Number of pages22
JournalJournal of Climate
Volume22
Issue number8
DOIs
Publication statusPublished - 2009 Jun 16

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annual cycle
rainfall
winter
monsoon
convection
gyre
ocean
sea surface temperature
moisture
rainband
moisture flux
atmosphere
trade wind
heat capacity
summer
insolation
phase transition
sea surface
advection
energy

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Annual cycle of rainfall in the western North Pacific and East Asian sector. / Chou, Chia; Huang, Li Fan; Tseng, Lishan; Tu, Jien Yi; Tan, Pei Hua.

In: Journal of Climate, Vol. 22, No. 8, 16.06.2009, p. 2073-2094.

Research output: Contribution to journalArticle

Chou, Chia ; Huang, Li Fan ; Tseng, Lishan ; Tu, Jien Yi ; Tan, Pei Hua. / Annual cycle of rainfall in the western North Pacific and East Asian sector. In: Journal of Climate. 2009 ; Vol. 22, No. 8. pp. 2073-2094.
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