Verification on the precipitable water vapor of GPS satellite signals

• Main Authors: Chine -Yung Shih, 許家維
• Other Authors: 葉大綱
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/81630778582625690566

碩士 === 清雲科技大學 === 空間資訊與防災研究所 === 98 === Abstract Water vapor is part of the evaporation process—a long existing physical phenomenon on earth. It transfers energy in the Nature as the weather changes, and is therefore less stable than other types of gasses in the atmosphere. Because of its instability, it affects people’s lives in both good and bad ways. If we can more effectively obtain information on Precipitable Water Vapor (PWV) in the atmosphere, we will be able to conduct more detailed researches and analyses about the weather and give more accurate forecasts. This research aims to measure water vapor in tropospheric zenith delay through signals received from the global positioning system (GPS). It also seeks to understand the relations between GPS and PWV through precipitation data. Bernese 5.0 is used to measure water vapor, and the wet delay data obtained through Water Vapor Radiometer (WVR) is used to verify such calculation. Results show that, in terms of measurement accuracy, WVR and GPS works just as well as one another, with their correlation coefficients standing over 0.9 and average errors between -1 and -2 mm. If comparing GPS measurement with that of the National Center for Atmospheric Research (NCAR), however, the NCAR statistics appear to have an underestimation of 5 to 6 mm. In other words, based on the WVR measurement, GPS appears to underestimate PWV by only 1 to 2 mm, while NCAR appears to underestimate PWV by 4 to 6 mm. In addition, there is often rain when PWV is high, such as 60 mm in plain areas and 40 mm in the mountains. We hope the statistical results of this research can not only help researchers understand more about the weather, but help improve the quality of weather forecasting in the future.