Abstract:In southern China the terrain is high in the west and low in the east, and there are differences between the coast and the inland. Using 19 sounding stations in southern China from 2015-2017, we analyze the relationship between Tm and station height, ground temperature, seasonal variation and latitude. For the annual sounding data, we establish a linear model (Tm-SC1) that only considers ground temperature and a new Tm model (Tm-SC2) related to ground temperature, elevation, seasonal changes, and latitude on the basis of the Bevis formula. Using the sounding data in 2018 as a reference, we analyze the accuracy of the models. We compare the accuracy with the widely used Bevis formula and GPT3 model. The results show that the average annual deviation and root mean square error (RMS) of the Tm-SC1 model are 0.76 K and 2.57 K, respectively. Compared with the Bevis model and the GPT3 model, the accuracy (RMS value) is increased by 13.8% and 2.2%, respectively. The annual average deviation and root mean square error (RMS) of the Tm-SC2 model are -0.10 K and 1.64 K, respectively. Compared with the Bevis model and the GPT3 model, the accuracy (RMS value) is increased by 44.9% and 37.6%, respectively. The theoretical RMS error and relative error of water vapor calculation caused by the Tm-SC2 model used in GNSS water vapor calculation are 0.16 mm and 0.43%, respectively. Therefore, the Tm-SC2 model is more suitable for GNSS water vapor detection and meteorological research in southern China.