Analysis of Atmospheric Boundary Layer lnversion Characteristics from 2003 to 2017 in Guiyang

The temperature inversion (TI) in atmospheric boundary layer is one of the main meteorological conditions related to atmospheric pollution. Based on the vertical high resolution sounding data of Guiyang upper air station from 2003 to 2017, the temporal variation characteristics of TI at Guiyang, including the frequency, thickness, intensity and bottom height of both surfacebased TI (SBI) and elevated TI (EI), are comprehensively analyzed. The results show that: (1) The TI exhibits small inter-annual variability in Guiyang is small but shows large seasonality with the most frequent TI in winter but least in summer, as well as the most in January but the least in July. (2) The annual frequency of elevated TI in Guiyang is eight times as large as that of the SBI, indicative of a much more frequent EI compared with SBI, which shows a “more frequent TI at high altitudes but less frequent TI at lower altitudes” pattern. On the whole, the SBI is mainly caused by radiative cooling and generally thought as radiative TI.The average monthly days experiencing TI in the morning and evening are 2.6 d and 0.5 d, respectively, indicating that there is not much SBI in Guiyang, and the weather conditions near the ground surface associated with air pollution are ideal. (3) The annual average intensity of SBI lies between 0.8-2.1 ℃/ 100 m, and the annual average intensity in the morning is less than that in the evening. The annual average intensity of EI is 1.0 ℃/ 100 m with small seasonal change due to the small range of 0.9-1.2 ℃/100m, and the maximum monthly average intensity of TI appears in July. The intensity and amplitude of SBI are both higher than those of EI, irrespective of season. (4) The seasonal and monthly height of the bottom of suspension inversion was lower in the morning than in the evening. The thickness of SBI and EI exhibit large seasonality: winter > spring > autumn > summer.