Abstract

China's air has become extremely polluted as a result of temperature inversions, which prevent momentum, heat, and moisture from moving through the atmosphere. Using sounding data from the past four decades, this study examined the spatiotemporal variation in temperature inversions in China. In a single sounding dataset, surfacebased, elevated, and both types of inversion were examined. The inversion parameters were subjected to frequency, strength, and depth statistical analyses. At six stations representing various climate zones Beijing, Harbin, Haikou, Shaowu, Ruoqiang, and Xining the annual frequency of total inversions did not show any significant trend of increasing or decreasing, with mean values of 0.78, 0.33, 0.24, 0.28, 0.5, and 0.36, respectively. There were downward trends in the annual inversion strength and depth. The frequency and strength of the monthly variation in inversion varied between stations. Summertime in Beijing and Harbin saw the weakest surface-based inversion, with mean values of 1 and 1.3°C; winter had the strongest surface-based inversion, with mean values of 3.5 and 3.6°C. The monthly variation in inversion depth, with a minimum at the six respective stations of 165, 334, 135, 267, 363 and 420 meters and a maximum at the six stations of 250, 646, 140, 591, 806 and 664 meters, may be explained by higher surface temperature in the summer and subsidence above the ground in the winter. Absolute reversal was least successive in southwestern China, surface-based reversal was generally continuous in the north, and raised reversal was generally regular in the southeast. In the north, the strongest and deepest surface-based inversion predominated. There were no significant regional differences in elevated inversion strength. The southeast was dominated by the deepest elevated inversion. Accurate model simulations of temperature inversions and the interactions between aerosols and inversions should be the primary focus of future endeavors.