Simulation of Structural Features of Atmospheric Boundary Layer of Chengdu Urban Agglomeration

Abstract

In the present paper, features of the atmospheric boundary layer of Chengdu urban agglomeration were identified and transfer, diffusion and conversion rules of atmospheric pollutants in the boundary layer were analyzed by using the mesoscale meteorological model, WRF(Weather Research & Forecasting)to simulate the temporal and spatial distribution and features of the flow field, temperature field, humidity field, and atmospheric mixed layer height of Chengdu urban agglomeration. As a result, basic data were provided for developing the plan for the coordinated development of the urban agglomeration economy and environment. The simulation show that, in Sichuan Basin, south wind and east wind prevail on the near-ground surface and 850 hPa isobaric surface while west wind and southwest wind prevail on the 700 hPa isobaric surface. Under the influence of the mountains around the basin, the flow field on the near-ground surface forms circulation in the south of the basin. The atmosphere strongly exchanges in the vertical direction below 1500 m and the exchange becomes weaker upwards. The ground temperature field distribution is low in northwest and high in southeast. The urban heat island effect is obvious, and especially the “big heat island” occurs in the urban agglomeration. In winter, temperature inversion frequently happens. In terms of ground humidity field, in winter and spring, it is low in northwest and high in southeast, which is opposite in summer; in autumn, humidity is low in west and high in east. Regarding the mixed layer height of the study area, it reaches the minimum value in winter and the maximum value in summer; the daily mixed layer height reaches the maximum value between 14:00 and 15:00 and reaches the minimum value in the small hours.