High-resolution PWV characteristics and response to precipitation in Northwest China based on GNSS

We analyzed the overall variation, spatial distribution, and diurnal variation of precipitable water vapor (PWV) in Northwest China based on ground-based global navigation satellite systems (GNSS) water vapor detection, hourly surface precipitation, and ERA5 reanalysis data from March 2021 to March 2023. Then, we discussed how different meteorological factors influence PWV. The results show that: (1) In Northwest China, PWV is low in the west but high in the east. East of Northwest China frequently has high values, with an annual average of 28.21 mm at the center, whereas the central part of the Qinghai Plateau and Slopes frequently has low values. In Northwest China, especially East of Northwest China, PWV is negatively correlated with altitude. (2) The annual average PWV variation is unimodal in all precipitation climate zones. The average PWV decreases and reaches its minimum from November to March, increases rapidly and reaches its maximum in mid to early July, decreases gradually, decreases rapidly after September, and stabilizes at a low level thereafter. (3) The analysis of diurnal PWV variation at five representative stations in Northwest China indicates that the average diurnal PWV variation is affected by both diurnal and semidiurnal cycles. The semidiurnal cycle is prominent at Zhangye station in Hexi Corridor in autumn, and the diurnal cycle dominates at all other stations, with a variance contribution of the diurnal cycle of greater than 75% and an amplitude of 0.2–0.88 mm. The average diurnal PWV variation reaches its minimum at 08:00–12:00 and reaches its maximum at 16:00–21:00. The exact time that the average diurnal PWV variation reaches its minimum and maximum varies depending on the season. (4) In Northwest China, in summer, the average PWV on days with precipitation is higher than on days without precipitation. PWV increases with the increase in precipitation, most significantly in summer and autumn. However, this increase is not significant when precipitation is smaller than 10 mm. Moreover, the PWV increase with precipitation is not prominent in South and North Xinjiang.