Trends and Variability in Precipitable Water Vapor throughout North China from 1979 to 2015

Wang Peng,Wu Yanling,Dai Xin,Song Qingli,Dai Jiageng,Song Dejun,Zhao Jinrong,Xie Tongchuan,Sun Jingmin,Yuan Hongliang

doi:10.1155/2017/7804823

Abstract

This study analyzed the variability and trends in precipitable water vapor (PWV) in North China from 1979 to 2015. The spatial distribution of annual mean PWV was generally characterized by two high PWV centers in Eastern China and the Tarim Basin and two low PWV centers in Northern Tibet and Qinghai Province and in Inner Mongolia. The levels of seasonal mean PWV were highest in summer, followed by autumn and spring, and lowest in winter. The maximum monthly mean PWV occurred in July and August, while the minimum occurred in December to February. Increasing trends in PWV, with the trend magnitude ranging from 0.1 to 1.2 mm decade−1 over North China, were observed in the radiosonde, ERA-interim, and MERRA-2 PWV data from 1979 to 1999; but a slightly decreasing trend of −0.4 mm decade−1 from radiosonde was found in most regions of North China from 1979 to 2007. A monotonically increasing PWV trend was detected throughout North China between 1979 and 1999, with the maximum trend occurring in summer and the minimum occurring in winter. For the period of 1979–2007, a slightly but less marked decreasing trend was found at most stations in North China in all four seasons.

Highlights

Water vapor plays a crucial role in climate change, hydrological processes, Earth’s energy balance, and weather systems [1,2,3]
Over the past few years, various studies have been performed to detect the changes in precipitable water vapor (PWV) using a variety of PWV datasets, which can be retrieved from various sensors such as Global Positioning System (GPS) receivers [10], radiosondes [6, 11], microwave radiometers [12, 13], Raman radar [14], multifilter rotating shadow band radiometers (MFRSR) [15], satellite remote sensing [16, 17], and ground-based sun photometry [18, 19]
The highest PWV level in North China occurred in July and August, with a PWV value of greater than 45 mm in Eastern China, greater than 18 mm in Xinjiang Province and Inner Mongolia, and greater than 9 mm in Northern Tibet and Qinghai Province, which was closely related to the enhanced intensity of the East Asian summer monsoon and increased evaporation resulting from increased temperature during this period

Summary

Introduction

Water vapor plays a crucial role in climate change, hydrological processes, Earth’s energy balance, and weather systems [1,2,3]. The long-term PWV observation records from radiosondes represent an important resource for monitoring the variation of atmospheric water vapor. It is difficult to quantify an accurate PWV trend from radiosonde PWV due to limitations such as incomplete and inhomogeneous observations and sparse spatial distributions [6, 23] Several factors such as changes in instrumentation, uncontrollable balloons, upgrades to instruments, and temporal inhomogeneities often cause spurious shifts in the radiosonde PWV time series [24]. The expected error in ground and satellite observations that are assimilated into a reanalysis system may propagate large biases in reanalysis products These errors may induce spurious long-term changes in reanalysis water vapor. The latest ERA-interim reanalysis products from ECMWF and the second Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) between 1979 and 2015 are exploited to derive PWV trends for a direct comparison with radiosonde data

Data and Method

Spatial Distribution and Variability of PWV throughout North China

Trends in PWV throughout North China

Conclusion