Charateristics of Precipitable Water Vapor in Arid Areas of the Hexi Corridor based on GPS Measurements

Abstract

There are obvious differences in spatial and temporal distribution characteristics of atmospheric water vapor and its relationship with precipitation under different topography and climate background conditions.Hexi Corridor located in inland arid region of Northwest China， so it is necessary to understand deeply and meticulously the changes of atmospheric precipitable water vapor.In this paper， based on precipitable water vapor data derived from ground-based GPS measurements （hereinafter referred to as GPS/PWV）， radiosonde data and ground conventional observation data at Zhangye National Climate Observatory from October 2016 to May 2019， the usability of GPS/PWV data was discussed firstly， then the temporal variation characteristics of PWV and its relationship with precipitation and surface water vapor pressure in arid area of the Hexi Corridor were analyzed.The results are as follows： （1） The GPS/PWV were higher consistent with calculated PWV by using radiosonde data.The root mean square error and average deviation were 2.01 mm and 1.16 mm respectively， and their correlation coefficient reached 0.97 and above.Therefore， GPS/PWV data had higher accuracy and availability.（2） The monthly distribution of atmospheric PWV appeared unimodal pattern， which was in good agreement with monthly precipitation.PWV was the maximum in August （23.24 mm） and the minimum in February （2.55 mm）.Precipitation was not only affected by PWV， but also related to precipitation conversion rate.The monthly precipitation peak behind the PWV peak because the precipitation conversion rate in July was higher than that in August.The diurnal variation of PWV was opposite to temperature， they had significantly negative correlation.The peak value of PWV appeared at 01:00 UTC， while the valley value appeared at 08:00 UTC.（3） The base value of PWV was 8.4 mm in arid area of the Hexi Corridor.When the rainfall occurs， PWV was mostly higher than the base value， and PWV increased sharply 7~11 hours before the precipitation， the increment generally exceeds 3.0 mm.The most rainfall started around the maximum PWV and ended the rapidly decreasing stage of PWV， and the maximum precipitation intensity and PWV appeared concurrently， or the maximum precipitation intensity was typically 1 hour behind the maximum PWV， which could be used as a reference index for precipitation forecast.（4） PWV on rainy days was significantly higher than that on non-rainy days.The analysis also showed that PWV had no obvious significance for the indication of snowy weather in arid areas.（5） There was a quadratic polynomial relationship between PWV and surface water vapor pressure in arid area of the Hexi Corridor.

Keywords

• arid area of the hexi corridor
• precipitable water vapor
• ground-based gps
• temporal variation characteristics