ANALYSIS ON EFFECT OF SOUTH ASIA HIGH ON MID-SUMMER EXTREME DROUGHT AND FLOOD IN SICHUAN-CHONGQING REGION

CHEN Yong-ren; LI Yue-qing; QI Dong-mei

Abstract:

NCEP/NCAR data are utilized to analyze an extreme flood year (1998) and an extreme dry year (2006) in the Sichuan-Chongqing region (SCR) and the results are as follows. The positive divergence of South Asia High (SAH) is stronger in the flood year; the position of the ridge line of SAH is southward compared with the annual average; Western Pacific Subtropical High (WPSH) extends westward and its ridge line is southward. In the drought year, the positive divergence of SAH is weaker, its ridge line is northward, and the position of WPSH is also northward. As shown in the dynamics, in drought (flood) years, negative (positive) vorticity advection in the upper atmosphere can cause the atmosphere to ascend (descend), and anomalous circulation of SAH displays divergence (convergence), and anomalous circulation of the lower atmosphere shows convergence (divergence). Thermal structure of the atmosphere shows that there is warm (cold) temperature advection in the lower atmosphere, and the vertical distribution of diabetic heating causes SAH’s local circulation to display convergence (divergence) and affects vertical motion of the lower atmosphere circulation eventually. To some extent, the two extreme years in the SCR is closely related to the vertical motion of atmosphere circulation and the variation of such vertical motion is caused by differences of interactions between SAH and lower atmosphere circulations.

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CHEN Yong-ren, LI Yue-qing, QI Dong-mei. ANALYSIS ON EFFECT OF SOUTH ASIA HIGH ON MID-SUMMER EXTREME DROUGHT AND FLOOD IN SICHUAN-CHONGQING REGION [J]. Journal of Tropical Meteorology, 2014, 20(2): 163-172.

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ANALYSIS ON EFFECT OF SOUTH ASIA HIGH ON MID-SUMMER EXTREME DROUGHT AND FLOOD IN SICHUAN-CHONGQING REGION

Institute of Plateau Meteorology, China Meteorological Administration, Chengdu 610072 China Sichuan Provincial Meteorological Observatory, Chengdu 610072 China

Rev Recd Date: 2014-03-07

Abstract: NCEP/NCAR data are utilized to analyze an extreme flood year (1998) and an extreme dry year (2006) in the Sichuan-Chongqing region (SCR) and the results are as follows. The positive divergence of South Asia High (SAH) is stronger in the flood year; the position of the ridge line of SAH is southward compared with the annual average; Western Pacific Subtropical High (WPSH) extends westward and its ridge line is southward. In the drought year, the positive divergence of SAH is weaker, its ridge line is northward, and the position of WPSH is also northward. As shown in the dynamics, in drought (flood) years, negative (positive) vorticity advection in the upper atmosphere can cause the atmosphere to ascend (descend), and anomalous circulation of SAH displays divergence (convergence), and anomalous circulation of the lower atmosphere shows convergence (divergence). Thermal structure of the atmosphere shows that there is warm (cold) temperature advection in the lower atmosphere, and the vertical distribution of diabetic heating causes SAH’s local circulation to display convergence (divergence) and affects vertical motion of the lower atmosphere circulation eventually. To some extent, the two extreme years in the SCR is closely related to the vertical motion of atmosphere circulation and the variation of such vertical motion is caused by differences of interactions between SAH and lower atmosphere circulations.

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Reference (22)

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ANALYSIS ON EFFECT OF SOUTH ASIA HIGH ON MID-SUMMER EXTREME DROUGHT AND FLOOD IN SICHUAN-CHONGQING REGION

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