Remote Sensing of Precipitable Water Vapor using GPS tropospheric delay in Argentina

LAURA FERNANDEZ; PAOLA SALIO; MARIA PAULA NATALI; AMALIA MEZA

Buenos Aires - Argentina

Congreso; IAG (International Association of Geodesy) Meeting: Geodesy for Planet Earth; 2009

International Association of Geodesy

Abstract: Atmospheric Precipitable Water Vapor (PWV) is one of the key components in determining and predicting the global climate system and its changes. These studies are crucial in order to understand the incidence of the humidity on precipitation. In fact water vapor is a highly variable parameter that plays a very important role in atmospheric processes. The operational weather measurements of the water vapor usually show limitations such as deficient temporal and spatial coverage. On the other hand, its determination from satellites measurements is not available on heavy clouds areas. PWV values obtained from ground-based Global Positioning System (GPS) networks have been proposed as an alternative reliable data source. GPS receivers are portable and more economic than the Water Vapor Radiometers (WVR). Besides, the GPS measurements can be obtained under any climatic condition including rain, storms and snow. Thus, although PWV estimated from GPS tropospheric delays (PWV GPS) do not provide the profile of water vapor as other techniques, it improves the temporal resolution. In this work, we present PWV GPS values computed on four GPS permanent stations in Argentina. The stations are located in different climate regimes (i.e. Salta station has a dry winter while Rosario shows high values of moisture during the whole year). In order to represent the four seasons, the study takes minimal periods of two weeks distributed during January to September, 2007. In particular we analyze the behavior of the PWV GPS estimation when applying different strategies for computing the mean tropospheric temperature (Tm): a) the classical Bevis model (Bevis et al., 1992); b) Tm is computed from the Global Assimilation Data System (GADS) and c) Tm is extrapolated from Sapucci model (Sapucci, 2004), which is valid for the southern part of Brazil. In order to validate the obtained results, we analyze the agreement among PWV GPS estimations with respect to PWV values obtained from balloon-borne radio soundings (PWV RS) and computed from satellite data from NOAA 18 mission (PWV NOAA). From the analysis we can conclude that the application of Sapucci model does not represent a significant improvement in precision with respect to the PWV GPS values estimated with Tm computed from GADS (named as PWV GPS Analysis). Besides the PWV GPS values shows a very good agreement with respect to the PWV RS determinations. Keywords: (GPS);(PWV); Mean Tropospheric Temperature (Tm)