Error analysis of precipitable water vapor by GPS/MET and its application in precipitation forecast
WANG Hong, ZHANG Enhong, MENG Jin, XU Xiaolin
1. Shandong Provincial Meteorological Information Center, 250031, Jinan, China; 2. Guangdong Meteorological Observation Data Center, 510080, Guangzhou, China
Abstract:[Background] The products of Precipitable Water Vapor (PWV) retrieved by GPS/MET (GPS/Meteorology) have the advantages of near real-time and for all-weather, etc., which provide more data sets for network monitoring in soil and water conservation field, thus, the data quality and the role of PWV is particularly important in precipitation forecast. [Methods] Comparing the PWV retrieved by GPS/MET with those observed by sounding and microwave radiometer, the data quality of GPS/MET was analyzed. The relationship of PWV retrieved by GPS/MET and ground precipitation was analyzed, and the role of PWV in precipitation forecast was investigated. The PWV data sets used in the paper which contained GPS/MET, sounding and microwave radiometer detections were observed in 2015 at Zhangqiu station located at Jinan, capital of Shandong province, an eastern city of China. The data set of rain intensity recorded by ground automatic weather stations was also used. [Results]1) The evolution trend of PWV retrieved by GPS/MET, sounding and microwave radiometer in 2015 was consistent, and peaks and troughs presented a well correspondence. Throughout the year, there was a clear monthly variation of PWV, showing a single peak distribution with time. Therefore, GPS/MET may reflect the variation of PWV in the atmosphere over time. 2) Although the biases between GPS/MET, microwave radiometer and sounding were large, the dispersion degree was not large, indicating that there was a systematic error between GPS/MET and the other two methods. 3) PWV started to increase about 10 hours before precipitation to the ground, and then maintained at a large value, indicating that the there was an obvious process of water vapor accumulation before rainfall. PWV reached the max value while precipitation started, the max rain intensity corresponded to max PWV well. After precipitation ended, the PWV fell rapidly. 4) The max PWV was the prerequisite of rainfall. The greater PWV value observed by GPS than average was, the larger the probability of precipitation was. For Zhangqiu station, considering the times and probability of precipitation comprehensively, the PWV increasing more than 6mm in consecutive 4 hours was selected to be an evidence of the precipitation happening. [Conclusions]Based on the well matching of PWV observed by GPS with the other two detections (sounding and microwave radiometer), PWV data set retrieved by GPS/MET was reliable,and played an indicative role in precipitation forecast by analyzing the relationship between PWV and rain intensity. As an interdisciplinary link between meteorology and soil and water conservation field, GPS/MET may provide data support for decision-making section and in soil and water conservation practice.
王洪1, 张恩红2, 孟金1, 徐晓琳1. GPS/MET误差分析及其在降水预报中的应用[J]. 中国水土保持科学, 2017, 15(2): 85-91.
WANG Hong, ZHANG Enhong, MENG Jin, XU Xiaolin. Error analysis of precipitable water vapor by GPS/MET and its application in precipitation forecast. SSWC, 2017, 15(2): 85-91.
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