The relationship between the low-frequency oscillation atmospheric heating source/sink and the drought in the Sichuan-Chongqing region in summer of 2006
In the summer of 2006, the severe drought occurred in the Sichuan-Chongqing region. In order to investigate the cause, using the NCEP/NCAR reanalysis data and the observed daily rainfall from the gauge stations, the relationship of the low-frequency oscillation (LFO) atmospheric heating source/sink with the severe drought in the Sichuan-Chongqing region in the summer of 2006 has been studied. The results show that the summer rainfall in 2006 over the Sichuan-Chongqing region was dominated by the about 60 day oscillation; during the period of the severe drought in the Sichuan-Chongqing region from late July to early August, longitudinally, due to the influences of the LFO heat sink over the Sichuan-Chongqing region and the LFO heat source over the Guangxi, Hainan and west of the region, there was a low-frequency meridional circulation cell formed over the region between the 15°N and 40°N, whose downward branch of the circulation cell is just located over the Sichuan-Chongqing region; latitudinally, under the joint influences of the LFO heat sink over the Taiwan and its surrounding areas and the LFO heat source west of the Taiwan and its surrounding areas, the low-frequency zonal circulation cell was formed over the region between 105°E and 130°E and another secondary low-frequency zonal circulation cell emergenced over the region between 85°E and 105°E, which strengthened the low-frequency upward motion over the Guangxi and Hainan and west of the region, and thus further strengthened the low-frequency meridional circulation that was formed over the region between the 15°N and 40°N. As a result, on the one hand, it strengthened the low-frequency downward flow over the Sichuan-Chongqing region and, on the other hand, also strengthened the low-frequency divergence of the low-level flow over the Sichuan-Chongqing region. The difference of zonal distribution of the LFO further strengthened the downward flow over the Sichuan-Chongqing region, which might be the important cause why over the Sichuan-Chongqing region the severe drought occurred in the summer of 2006.
国家科技期刊平台
NSTL
万方数据
维普
