Change Of Precipitable Water Vapor Research Articles

Remote sensing of atmospheric water vapor variation from GPS measurements during a severe weather event

Abstract The Global Positioning System (GPS) provides a relatively inexpensive method to remotely sense atmospheric water vapor in all weather conditions. In this study, we applied the GPS meteorology technique to monitor the precipitable water vapor (PWV) variation during a severe weather event (typhoon EWINIAR). The Korean weighted mean temperature equation (KWMTE), customized for the Korean Peninsula, was used to improve the accuracy of the GPS PWV estimation. The time series and the comparison with the images of MTSAT/CMAX and the GPS PWV contour maps indicated that the temporal change of GPS PWV was closely related to the progress of the typhoon. The correlation between the maximum GPS PWV and the maximum rainfall caused by the typhoon was also higher than that for the quiet weather period. Furthermore, the peak in the time series of GPS PWV was generally in good agreement with the time when the maximum rainfall was recorded. Our results therefore confirm that GPS meteorology is an efficient PWV sensing technique, capable of capturing the complex characteristics of water vapor distribution and its temporal variation during a period of severe weather events.

Retrieval of the change of precipitable water vapor with zenith tropospheric delay in the Chinese mainland

As a preliminary step for assessing the impact of global positioning system (GPS) refractive delay data in numerical weather prediction (NWP) models, the GPS zenith tropospheric delays (ZTD) are analyzed from 28 permanent GPS sites in the Chinese mainland. The objectives are to estimate the GPS ZTD and their variability in this area. The differences between radiosonde precipitable water vapor (PWV) and GPS PWV have a standard deviation of 4 mm in delay, a bias of 0.24 mm in delay, and a correlation coefficient of 0.94. The correlation between GPS ZTD and radiosonde PWV amounts to 0.89, indicating that the variety of tropospheric zenith delay can reflect the change of precipitable water vapor. The good agreement also guarantees that the information provided by GPS will benefit the NWP models. The time series of GPS ZTD, which were derived continuously from 2002 to 2004, are used to analyze the change of precipitable water vapor in Chinese mainland. It shows that the general trend of GPS ZTD is diminishing from the south-east coastland to the north-west inland, which is in accordance with the distribution of Chinese annual amount of rainfall. The temporal distribution of GPS ZTD in the Chinese mainland is that the GPS ZTD reaches maximum in summer, and it reaches minimum in winter. The long term differences between the observational data sources require further study before GPS derived data become useful for climate studies.

Retrieval of the change of precipitable water vapor by GPS technique

The feasibility of GPS precipitable water vapor (PWV) is discussed based on the comparison of Radiosonde and GPS PWV where the correlation coefficient is 0.94 and the RMS is 4.0 mm. PWV change in the Chinese mainland in 2004 is graphed with the gridding method of splines in tension, according to the GPS data of the crust monitor observation network in China, combined with relevant meteorology information. According to the distribution of the annual amount of rainfall in the country, it can be concluded that the total trend of the PWV is diminishing from the south-east coastland to the north-west inland. The PWV reaches its maximum during July and August, and the minimum is reached during January and February. According to the PWV, from high to low, all districts can be ranked as south-east coastland, the inland and the tableland.