Precipitable water vapor on the Tibetan Plateau estimated by GPS, water vapor radiometer, radiosonde, and numerical weather prediction analysis and its impact on the radiation budget

Abstract

[1] Precipitable water vapor amounts (PW) determined by Global Positioning System (GPS), radiosonde and operational numerical weather prediction (NWP) system analysis at three stations (Naqu, Gaize, and Deqin) on the Tibetan Plateau are compared. PW measured by water vapor radiometer at Naqu and a low-elevation site, Xian, is used for calibration. The results show that the PW determined by NWP analysis in these regions is comparable with that of the radiosonde measurements but that they both are systematically smaller than those determined by the GPS measurements. The averaged difference of PW between GPS and radiosonde estimates is about 1.75 mm, and that between GPS and NWP analysis can be as large as 7.75 mm. These differences are relatively larger than those reported in the literature because the absolute PW in this region is much smaller. The effect of such large differences on the surface radiation budget is evaluated using a radiation model. The results show that both longwave and shortwave radiative fluxes at the surface determined using the model analysis profiles with the water vapor corrected by the GPS PW are closer to the observations compared with those without water vapor correction. The flux difference at the surface with and without water vapor correction is about 20 W m À2 in the shortwave and 30 W m À2 in the longwave. These differences are much larger than that caused by doubling the concentration of carbon dioxide in the atmosphere in this region.Citation: Liu, J., Z. Sun, H. Liang, X. Xu, and P. Wu (2005), Precipitable water vapor on the Tibetan Plateau estimated by GPS, water vapor radiometer, radiosonde, and numerical weather prediction analysis and its impact on the radiation budget,

Evaluation of AIRS Precipitable Water Vapor against Ground-based GPS Measurements over the Tibetan Plateau and Its Surroundings

“…In the monsoon season, the water vapor intrudes into the central and eastern TP, bringing summer precipitation. Moreover, the eastward movement of convective cloud systems developing over the TP may cause severe floods in east and southeast China (Liu et al 2005). Thus, it is very significant to monitor the amount of precipitable water vapor (PWV) and its spatial and temporal variations in this area.…”

“…Many studies showed that PWV data can be continuously derived from GPS signals according to their delays in the atmosphere with high accuracy at relatively low costs (Kuwagata et al 2001). Thus, GPS-based PWV data is often used to validate satellite-based PWV retrievals and PWV reanalysis data from numerical weather prediction models (Bock et al 2007;Liu et al 2005;Noel et al 2005). GPS-based PWV data has already been compared with AIRS PWV product in many validation tasks.…”

Estimation of hourly solar radiation at the surface under cloudless conditions on the Tibetan Plateau using a simple radiation model

“…The observational technique, based on the Global Positioning System (GPS) and is sensitive to the spatial and temporal distribution of the water vapor content in the atmosphere, has made it possible to retrieve precise and continuous estimates of water vapor with spatial density governed by the number of receivers deployed (Bevis et al, 1994;Wang and Zhang, 2008). The accuracy of GPS-derived PW has been shown to be near that of measurements by a water vapor radiometer and better than that of observations from radiosonde (Liou et al, 2001;Sapucci et al, 2005;Guerova et al, 2005;Baelen et al, 2005;Liu et al, 2005;Pacione and Vespe, 2008). The advantages of GPS-derived PW include data available under all weather conditions, high temporal resolution (5-min to 2-h intervals), high accuracy (< 3 mm in PW), and long-term stability (Wang and Zhang, 2008).…”

“…The uncertainties of the water vapor measured by radiosonde and retrieved by Moderate-Resolution Imaging Spectroradiometer (MODIS) on the Plateau have been discussed in many studies (e.g., Takagi et al, 2000;Liu et al, 2005Liu et al, , 2006. Lack of precise and continuous water vapor observations is one of the major sources of error in numerical weather prediction models (Liu et al, 2005).…”

An improved troposphere tomographic approach considering the signals coming from the side face of the tomographic area

“…Atmospheric water vapour only accounts for a small proportion of total atmospheric volume, but it plays an important role in the formation of clouds and rainfall, as well as the evolution of weather systems (Liu et al, 2005;Wang et al, 2014). Knowing precise information about the spatiotemporal distribution of water vapour is a prerequisite for atmospheric research (Emanuel et al, 1995;Park et al, 1999;Bauer et al, 2011;Ducroco et al, 2002).…”