Diagnostic Analysis of Wind Fields and Atmospheric Transport Pathways in the Guanzhong Basin

The characteristics of wind fields and transport pathways in the Guanzhong Basin were revealed based on data from 151 surface meteorological stations in 2017. Wind speed and wind direction data from five representative stations in the basin were analyzed by calculating windy days, daily average wind speed and wind direction frequency in four seasons, and hourly wind field and transport trajectories were calculated by CALMET and trajectory model. The results show that daily average wind speed in the Guanzhong Basin is about 1−3 m s^-1, which is higher in summer but lower in autumn and winter. The dominant wind direction in the center of the basin mainly includes northeast and southwest winds along the terrain, while the dominant wind direction around the basin shows a converging trend along the terrain to the center of the basin. Seasonal changes in dominant wind direction at each station are not significant. The wind fields in the basin can be classified into three types, namely, systematic wind field, feeblish systematic wind field, and local atmospheric circulation. The local atmospheric circulation occurs most frequently in the year (74.7%), followed by feeblish systematic wind field (17.3%), and systematic wind field (8%). Airflows of systematic wind field are mainly transported northeasterly, while airflows of feeblish systematic wind field or local atmospheric circulation are transported northeasterly, westerly (including southwesterly), and southeasterly. Trajectories of the local atmospheric circulation are limited to a small area, concentrated between the central basin and southern mountains, which indicates that this wind field is not conducive to air pollution dispersion.