Analysis of Wind Field Characteristics within the Lower Atmosphere in Urban and Suburban Areas of Beijing in 2018

Based on the Doppler sodar data observed at the Huabei Xianghe full atmosphere field scientific observation and research station and the wind profiler data obtained from the Beijing national comprehensive meteorological observation and test base during 1 January to 31 December 2018, this study compares and analyzes the wind field characteristics within the lower atmosphere in the urban and suburban areas of Beijing. Results show that in the aspect of the vertical structure, the horizontal wind speed increases gradually with height. At the same altitude, the average horizontal wind speed in the suburban area is more than that in the urban area, and the diurnal variation of the horizontal wind speed in the urban and suburban areas is smaller in the daytime than that in the nighttime. In spring and summer, the horizontal wind direction in the urban area is south–southwest, which is significantly affected by the valley–mountain breeze. The horizontal wind direction in the urban and suburban areas is northwest in autumn and winter, which is affected by the cold air activity. Additionally, the diurnal variation of horizontal wind direction changes seasonally. Vertical wind speed distribution characteristics of the lower atmosphere in the suburban area are the same in the four seasons, the frequencies of positive and negative speeds are similar, and the diurnal variation trend is single-peak. However, there are differences between winter and spring vertical wind speeds in the urban area. The frequency of positive speed below the altitude of 390 m is obviously greater than that of negative speed, and the diurnal variation trends are quite different in the four seasons. Compared with other megacities, the difference in wind field characteristics between urban and suburban areas of Beijing is not special, which is primarily affected by atmospheric circulation, local topography, and land surface environment.