Analysis of Precipitable Water Estimates Using Permanent GPS Station Data During the Athens Heavy Rainfall on February 22th 2013

Abstract

The Global Positioning System (GPS) has been used in the remote sensing of the atmosphere. A significant component of the atmosphere that affects the GPS signals is the zenith tropospheric delay (ZTD). The computation of ZTD estimates can directly or indirectly reflect weather variations. Through the analysis of ZTD values the hydrostatic and wet component of the total delay can be determined. For example, the wet tropospheric delay could be derived by subtracting the hydrostatic from the total delay. Hydrostatic delay can be estimated from surface or other meteorological data. The wet tropospheric delay can then be used in the derivation of the amount of precipitable water. Precipitable water plays a significant role in the physical and chemical processes of the atmosphere. It also greatly contributes to studies of weather forecasting and climate change. In this study GPS data from 12 permanent stations covering the broader area of the city of Athens, between February 18th and 24th, were used. This period was selected because of a heavy rainfall event on February 22nd. Data were processed using the GAMIT software and precipitable water (PW) estimates with 1 h time interval were derived. The PW values were analyzed in combination with meteorological data such as cloudiness, wind direction and precipitation obtained from the Hellenic Center for Marine Research and the Hydrological Observatory of Athens. The results indicate consistency between the estimated PW values and the related meteorological observations. This study suggests that a continuous record of PW estimates and meteorological variables is highly recommended for further studies on the behavior of the atmospheric water vapor and its contribution to the climate monitoring.