Search

The southwest vortices (SWVs) are a unique type of mesoscale vortex that frequently induce torrential rainfall in China. In this study, we focused a long‐lived quasi‐stationary SWV, which was the primary system for producing an extremely heavy rainstorm within/around Sichuan (the maximum hourly precipitation was ~103.8 mm) in Mid July 2021. After reproduced the SWV's formation by using Weather Research and Forecasting model, we conducted trajectory analyses and topography sensitivity simulations to understand the effects of complicated topography on the vortex's formation. It is found that, the regions south and southwest of the SWV acted as the most important source regions for the air clusters that formed the SWV (proportion ≥ 65%), and the air clusters originated from the upper layer contributed the most (≥60%). Of these, the air clusters sourced from the upper layer southwest and south of the SWV played the most important role in the SWV's formation, as their increase in cyclonic vorticity and their contributions to trajectory number and vorticity were all much larger than those of the others. Sensitivity simulations indicated that, detailed topography features around the Sichuan Basin were crucial in determining the structure, intensity and precipitation of the SWV, whereas, the topography features were not a decisive factor for the SWV's formation. In summary, our findings are useful to enrich the current understanding of the SWVs' formation, which would be helpful to improve the related forecasts. [ABSTRACT FROM AUTHOR]

Accurate meteorological fields and applicable air quality models are important ways to optimize air pollution simulations. To improve the accuracy of winter air pollution models in the Sichuan basin, we conducted a meteorological field simulation using 25 sets of parameterized scheme combinations in the Weather Research and Forecasting (WRF) Model. Based on the optimal parameters, the air pollution levels were simulated using AERMOD and CALPUFF models in a local large steel plant, and the data were verified by comparing the data from four National Ambient Air Monitoring Stations (NAAMS). The results indicated that the WRF model parameters had substantial effects on the simulation of the ground wind field, high-altitude wind field, and ground humidity field. In contrast, the parameters had no significant effect on the simulation of the ground temperature field, high-altitude temperature field, and high-altitude humidity field. The combination of the SLAB land surface process scheme and Dudhia shortwave radiation scheme with four boundary layer schemes, namely YSU, ACM2, BouLac, and MRF, could well-simulate the trends of winter surface wind, temperature, and humidity fields in Sichuan basin. The simulation results were analyzed by combining the statistical parameters of high-altitude wind, temperature, and humidity. The group 1 parameter scheme was applicable to simulate the meteorological field of Dazhou. Group 13 and Group 17 parameters were applicable to simulate the meteorological fields in Chengdu during the day and night, respectively. The correlation between CALPUFF simulation and monitoring value was better than that for AERMOD. CALPUFF was more accurate than AERMOD when referring to the monitoring data from NAAMS No.3. In addition, the simulation quality of CALPUFF was slightly better than that of AERMOD with reference to data from NAAMS No.2. Using air pollutant monitoring data from NAAMS as a reference, the simulated results of CALPUFF on NO x and PM 10 were improved compared to AERMOD at all four stations. Data from the Q-Q diagram indicated that the simulated results of CALPUFF on SO 2 , NO x , and PM 10 were closer to the monitored values compared to those of AERMOD.