Abstract
The southwest vortex (SWV), a low-pressure system bringing severe rainfall in southwest China, is one of the most important synoptic systems in China. Using both the National Centers for Environmental Prediction Final (NCEP-FNL) operational global analysis dataset and the Weather Research and Forecasting (WRF) model simulation, a sophisticated SWV with dual-core structure (DCSWV) over the Sichuan Basin in 2010 was studied. The DCSWV system consisted of two cores, one near Leshan City (named “C1”) and another near Langzhong City (named “C2”). The high-resolution WRF model reproduced the life cycle of the DCSWV well. The diagnostic analysis of the vorticity budget indicated that the stretching and tilting terms played important roles in the development stage of “C1”, while the stretching and vertical advection of vorticity were the major contributors to the formation and development stage of “C2”, which implied the importance of moisture convergence and ascending motion. Sensitivity experiments showed that the DCSWV was closely associated with the release in latent heat as well as the effect of topography. The great release in latent heat provided significantly positive feedback to the DCSWV system, which was decisive to the formation and development stages of “C2”. The topography of the Tibetan Plateau and the Yun-Gui Plateau affected the location and duration of the DCSWV.
Highlights
Sichuan Basin (SCB), a fertile expanse with low hills and plains almost entirely encircled by mountains, is located in the east of Tibetan Plateau (TP), west of Wu Mountain, north of Yun-Gui Plateau, and south of Daba Mountains, China (Figure 1A)
ZW, HL, KC, KW, and WZ contributed to the discussion of the results
Summary
Sichuan Basin (SCB), a fertile expanse with low hills and plains almost entirely encircled by mountains, is located in the east of Tibetan Plateau (TP), west of Wu Mountain, north of Yun-Gui Plateau, and south of Daba Mountains, China (Figure 1A). Previous studies suggested that the latent heat and topography can largely contribute to the initiation and intensification of the typical SWV (Ye and Gao, 1979; Ye, 1981; Wu and Chen, 1985; Chen and Dell’Osso, 1984; Kuo et al, 1986; Lu, 1986; Wang and Orlanski, 1987; Raymond and Jiang, 1990; Kuo et al, 1988; Fu et al, 2010; Jiang et al, 2012; Li et al, 2017). How about their roles in the DCSWV? The brightness temperature data (hourly, 0.05° × 0.05°) is obtained from Japan’s second Multifunctional Transport Satellite (MTSAT2) IR1 instrument (Takeuchi et al, 2007)
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