Home Articles Application of Global Positioning system in Water Vapor Estimation

Application of Global Positioning system in Water Vapor Estimation

Prof. M.N. Kulkarni Professor
Indian Institute of Technology ,Powai Mumbai.,
India
Email: [email protected]

Prof.M.N.Kulkarni
Professor
IIT Mumbai
Email: [email protected]

Dr.S.S.Gedam
Professor
Centre for Studies in Resources Engineering
Email: [email protected]

Rajiv G.Kurekar
IIT Mumbai
Email: [email protected]

Global Positioning System (GPS) is a satellite based navigation system, designed to provide instantaneous position, velocity and time information on the surface of the Earth at any time in any weather condition. GPS has become an effective tool in various applications related to the earth observation. GPS radio waves are delayed due to the ionosphere and troposphere. For positioning this is the source of error, but it has been found that tropospheric delay is due to the composition of gases and water vapor present in the troposphere.GPS can be used effectively for determining the amount of total water vapor, which in turn can be used for monitoring the flood, short-term weather forecast, and various atmospheric studies. The total water vapor content can be determined by using the GPS data and formulating suitable model of the troposphere. The temperature, pressure, and the relative humidity can be measured by using precise meteorological instrument called MET3A on the surface of the earth. The integrated total water vapor content can be computed from the zenith equivalent total path delay affecting the radio signal propagation in the troposphere. The zenith total delay will be decomposed in to the zenith wet delay (ZWD) and zenith hydrostatic delay (ZHD). The ZWD is found out by subtracting ZHD, from zenith total delay (ZTD). ZHD is computed by using suitable atmospheric model. ZWD can be converted in to precipitable water vapor (PWV). The objective of this study is the integration of the GPS Receiver with meteorological instrument called the MET3A. To determine the zenith total troposphere delay using GAMIT software in near real time. The validation of the Saastamonion model for ZHD determination has been carried out. Regression model has been developed for the determination of the ZHD for IIT Bombay station using radiosonde data for year 2005.ZWD has been calculated by subtracting ZHD from the ZTD.ZWD has been converted into PWV using the function ¡Ç which is defined by the atmospheric mean temperature. The comparison is made between the observed radiosonde values and the one which are obtained using GPS data.
Form the study it can be concluded that GPS methodology for the estimation of the PWV near real time solutions is possible as well as this is the more economical method for short term weather forecast over the traditional methods like radiosonde, sun photometer which are available for the estimation of the PWV.