In ground-based GPS meteorology, Tm is a key parameter to calculate the conversion factor that can convert the zenith wet delay(ZWD) to precipitable water vapor(PWV). It is generally acknowledged that Tm is in an ...In ground-based GPS meteorology, Tm is a key parameter to calculate the conversion factor that can convert the zenith wet delay(ZWD) to precipitable water vapor(PWV). It is generally acknowledged that Tm is in an approximate linear relationship with surface temperature Ts, and the relationship presents regional variation. This paper employed sliding average method to calculate correlation coefficients and linear regression coefficients between Tm and Ts at every 2°× 2.5° grid point using Ts data from European Centre for Medium-Range Weather Forecasts(ECMWF) and Tm data from "GGOS Atmosphere", yielding the grid and bilinear interpolation-based Tm Grid model. Tested by Tm and Ts grid data, Constellation Observation System of Meteorology, Ionosphere, and Climate(COSMIC) data and radiosonde data, the Tm Grid model shows a higher accuracy relative to the Bevis Tm-Ts relationship which is widely used nowadays. The Tm Grid model will be of certain practical value in high-precision PWV calculation.展开更多
The estimation of Precipitable Water Vapor (PWV) derived from Global Positioning System (GPS) data at the IGS site WUHN is assessed by comparing with PWV obtained from radiosonde data (No.57494) in Wuhan. The ap...The estimation of Precipitable Water Vapor (PWV) derived from Global Positioning System (GPS) data at the IGS site WUHN is assessed by comparing with PWV obtained from radiosonde data (No.57494) in Wuhan. The applicability of Saastamoinen (SAAS), Hopfield and Black models used for estimating Zenith Hydrostatic Delay (ZHD) and Zenith Wet Delay (ZWD) and different models is verified in the estimation of GPS-derived PWV for the applied area. The experimental results demonstrated that : 1 ) the precision of PWV estimated from Black model used for calculating ZHD ( ZHDs ) is lower than that of SAAS ( ZHDsAAs ) model and Hopfield model (ZHDn) with the RMS of 4. 16 ram; 2) the RMS of PWV estimated from SAAS model used for calculating ZWD (SAAS) is 3.78 ram; 3 ) the well-known Bevis model gives similar accuracy compared with the site-specific models for Tm in terms of surface temperature ( Ts ) and surface pressure (Ps), which can reach the accuracy inside 1 mm in the GPS-derived PWV estimates.展开更多
We present preliminary calibration results for Jason-3 and Sentinel-3A altimeters that we set up in the Wanshan Islands in Guandong Province,China.Two campaigns were carried out in 2018,from March 8 to April 16 and fr...We present preliminary calibration results for Jason-3 and Sentinel-3A altimeters that we set up in the Wanshan Islands in Guandong Province,China.Two campaigns were carried out in 2018,from March 8 to April 16 and from November 3 to December 11,2018.Three GPS reference stations and tide gauges were established on the islands of Zhiwan,Dangan,and Wailingding during the campaigns.The in-situ sea surface height(SSH)of the altimeter footprint was determined using the tide gauge.The tidal and geoid connection between the tide gauge locations and the altimeter footprints were computed with the NAO.99Jb tidal prediction system and the EGM 2008 geoid,respectively.The data of the tide gauges were defi ned using the GPS buoy and GPS reference stations during the campaigns.The results show that the waveform of the altimeters was slightly contaminated by the small islands.The bias associated with Jason-3 and Sentinel-3A amounted to approximately+20.7±49.7 mm and+30.1±39.4 mm,respectively,which agreed well with the results from other in-situ calibration fi elds.This indicates that the Wanshan area was very suitable as an in-situ calibration/validation fi eld.The wet zenith delay(WZD)determined from the Microwave Radiometer(MWR)and the GPS measurements diff ered from each other for the Jason-3 and Sentinel-3A by−6.6±7.4 mm and 0±6.8 mm,respectively.展开更多
基金supported by National Natural Science Foundation of China(41301377)by the Fundamental Research Funds for the Central Universities(2014214020202)by Surveying and Mapping Basic Research Program of National Administration of Surveying,Mapping and Geoinformation(13-02-09)
文摘In ground-based GPS meteorology, Tm is a key parameter to calculate the conversion factor that can convert the zenith wet delay(ZWD) to precipitable water vapor(PWV). It is generally acknowledged that Tm is in an approximate linear relationship with surface temperature Ts, and the relationship presents regional variation. This paper employed sliding average method to calculate correlation coefficients and linear regression coefficients between Tm and Ts at every 2°× 2.5° grid point using Ts data from European Centre for Medium-Range Weather Forecasts(ECMWF) and Tm data from "GGOS Atmosphere", yielding the grid and bilinear interpolation-based Tm Grid model. Tested by Tm and Ts grid data, Constellation Observation System of Meteorology, Ionosphere, and Climate(COSMIC) data and radiosonde data, the Tm Grid model shows a higher accuracy relative to the Bevis Tm-Ts relationship which is widely used nowadays. The Tm Grid model will be of certain practical value in high-precision PWV calculation.
基金supported by the National Natural Science Foundation of China(4106400141071294)+1 种基金Guangxi Key Laboratory of Spatial Information and Geomatics(GuiKeJi 1103108-06)the Natural Science Foundation of Guangxi(2012GXNSFAA053183)
文摘The estimation of Precipitable Water Vapor (PWV) derived from Global Positioning System (GPS) data at the IGS site WUHN is assessed by comparing with PWV obtained from radiosonde data (No.57494) in Wuhan. The applicability of Saastamoinen (SAAS), Hopfield and Black models used for estimating Zenith Hydrostatic Delay (ZHD) and Zenith Wet Delay (ZWD) and different models is verified in the estimation of GPS-derived PWV for the applied area. The experimental results demonstrated that : 1 ) the precision of PWV estimated from Black model used for calculating ZHD ( ZHDs ) is lower than that of SAAS ( ZHDsAAs ) model and Hopfield model (ZHDn) with the RMS of 4. 16 ram; 2) the RMS of PWV estimated from SAAS model used for calculating ZWD (SAAS) is 3.78 ram; 3 ) the well-known Bevis model gives similar accuracy compared with the site-specific models for Tm in terms of surface temperature ( Ts ) and surface pressure (Ps), which can reach the accuracy inside 1 mm in the GPS-derived PWV estimates.
基金Supported by the National Key R&D Program of China(No.2018YFB0504904)the National Natural Science Foundation of China(Nos.41406204,41501417)the Operational Support Service System For Natural Resources Satellite Remote Sensing。
文摘We present preliminary calibration results for Jason-3 and Sentinel-3A altimeters that we set up in the Wanshan Islands in Guandong Province,China.Two campaigns were carried out in 2018,from March 8 to April 16 and from November 3 to December 11,2018.Three GPS reference stations and tide gauges were established on the islands of Zhiwan,Dangan,and Wailingding during the campaigns.The in-situ sea surface height(SSH)of the altimeter footprint was determined using the tide gauge.The tidal and geoid connection between the tide gauge locations and the altimeter footprints were computed with the NAO.99Jb tidal prediction system and the EGM 2008 geoid,respectively.The data of the tide gauges were defi ned using the GPS buoy and GPS reference stations during the campaigns.The results show that the waveform of the altimeters was slightly contaminated by the small islands.The bias associated with Jason-3 and Sentinel-3A amounted to approximately+20.7±49.7 mm and+30.1±39.4 mm,respectively,which agreed well with the results from other in-situ calibration fi elds.This indicates that the Wanshan area was very suitable as an in-situ calibration/validation fi eld.The wet zenith delay(WZD)determined from the Microwave Radiometer(MWR)and the GPS measurements diff ered from each other for the Jason-3 and Sentinel-3A by−6.6±7.4 mm and 0±6.8 mm,respectively.