Establishment Of Atmospheric Precipitable Vapor Empirical Formula In LRGR (Longitudinal Range-Gorge Region), The Southeastern Extending Zone Of The Tibetan Plateau

Based on daily GPS remote sensing atmospheric precipitable water vapor data on 6 ground-based GPS stations in Longitudinal Range-Gorge Region (LRGR) from JICA(Japan International Cooperation Agency) program during the period of 2010-2013, tropospheric precipitable water vapor data calculated by observed data on 3 radiosonde stations at the same time and monthly average surface vapor pressure data on 17 ground stations from 1979 to 2014, firstly, error between ground-based GPS precipitable water vapor data at Tengchong, the representative station in LRGR, and its sounding atmospheric precipitable water vapor data is examined. Then empirical formula between surface vapor pressure and precipitable water vapor is established in both dry and wet season according to local climate characteristic. Also the accuracy of the fitting precipitable water vapor data by two empirical formula is tested. Finally, spatial and temporal distribution characteristics of precipitable water vapor in LRGR are analyzed based on fitting precipitable water vapor data. The main conclusions are as follows:(1)Ground-based GPS precipitable water vapor data almost coincides with the sounding precipitable water vapor data at Tengchong, Root mean square error (RMSE) between them is only 3.3mm, demonstrating GPS precipitable water vapor data in LRGR is highly reliable.(2)Error between GPS precipitable water vapor and sounding precipitable water vapor varies from wet to dry seas. That is, there is a high value of error during rich water vapor time (i.e. wet season or 12:00 UTC) and a low value in poor water vapor time (i.e. dry season or 00:00 UTC).And the error almost quadratically increases with air temperature rises.(3)Error of fitting precipitable water vapor data in dry and wet season is smaller than error of precipitable water vapor data fitted by other empirical formulas, as same as the results of reanalysis precipitable water vapor data, especially in dry season.(4) Error of fitting precipitable water vapor increases as a quadratic curve during dry season and as a power function during wet season with altitude’s rising.(5) Precipitable water vapor decreases with the increase of latitude in LRGR, evident zonal (meridional) distribution is found in dry (wet) season. Additionally, precipitable water vapor in dry season linearly increases in southern and northern area of LRGR, but decreases in medium area, while linearly increases in northwestern area and decreases in southeastern area in wet season from 1979-2014.