Diurnal variation of GPS precipitable water at Lhasa in premonsoon and monsoon periods

In this study, precipitable water is estimated from GPS data with high time resolution at Lhasa. Mean precipitable water in the premonsoon and the monsoon periods are about 10 mm and 25 mm, respectively, while precipitable water increases in short term at around the onset. Prominent diurnal variation of precipitable water can be observed in both periods. The minima of the diurnal variation appear around 1800 LST and 1500 LST in the premonsoon and the monsoon periods, respectively. These characteristics indicate that the diurnal Variation of water vapor is strongly affected by the local circulation over the deep valley.