Weighted Mean Temperature Modelling Using Regional Radiosonde Observations for the Yangtze River Delta Region in China.

Precipitable water vapor can be estimated from the Global Navigation Satellite System (GNSS) signal's zenith wet delay (ZWD) by multiplying a conversion factor, which is a function of weighted mean temperature ( T m ) over the GNSS station. Obtaining T_m is an important step in GNSS precipitable water vapor (PWV) conversion. In this study, aiming at the problem that T_m is affected by space and time, observations from seven radiosonde stations in the Yangtze River Delta region of China during 2015−2016 were used to establish both linear and nonlinear multifactor regional T_m model (RTM). Compared with the Bevis model, the results showed that the bias of yearly one-factor RTM, two-factor RTM and three-factor RTM was reduced by 0.55 K, 0.68 K and 0.69 K, respectively. Meanwhile, the RMSE of yearly one-factor, two-factor and three-factor RTM was reduced by 0.56 K, 0.80 K and 0.83 K, respectively. Compared with the yearly three-factor linear RTM, the mean bias and RMSE of the linear seasonal three-factor RTMs decreased by 0.06 K and 0.10 K, respectively. The precision of nonlinear seasonal three-factor RTMs is comparable to linear seasonal three-factor RTMs, but the expressions of the linear RTMs are easier to use. Therefore, linear seasonal three-factor RTMs are more suitable for calculating T_m and are recommended to use for PWV conversion in the Yangtze River Delta region. [ABSTRACT FROM AUTHOR]