Abstract
Based on the atmospheric temperature and dew point temperature difference series of mandatory levels in the arid region of northwest China, we calculated the specific humidity of stations at 200, 300, 400, 500, 700, and 850 hPa and analyzed the spatial and temporal distribution. The specific humidity of radiosonde is compared with two sets of reanalysis data (ERA-interim from European Centre for Medium Range Weather Forecasts and Modern Era Retrospective Analysis for Research and Applications: MERRA-2). The annual specific humidity and summer specific humidity show a positive trend in the vertical atmospheric levels during the period 1958–2018. Taking the middle of the 1980s and 2002 as boundaries, the selected levels show the trend of “declining-gentle rising-fluctuation rising”. The maximum specific humidity is observed at the level of 850–700 hPa during the warm months of the year, and the most vertical expansion in specific humidity is in July. In terms of spatial distribution, the specific humidity is greatly influenced by the topography and underlying surface at lower levels. The characteristics of spatial distribution of the trend are well described by the two sets of reanalysis data in the middle and upper levels, but there are some deficiencies in depicting the trend in the lower levels.
Highlights
Water vapor in the atmosphere is the material basis for the formation of clouds and precipitation
Specific humidity is frequently used as a parameter to calculate water vapor transport flux, water vapor transport flux divergence, water vapor budget, and latent heat flux in the atmosphere [10,11,12,13,14,15,16]
Analyzing tropospheric specific humidity is beneficial for deepening the knowledge of climate change, providing a foundation for analyzing regional water vapor content, water vapor budget, and other factors, as well as providing a basis for coping with regional climate change and improving the accuracy of forecasting and early warning
Summary
Water vapor in the atmosphere is the material basis for the formation of clouds and precipitation. Specific humidity is the ratio of mass between water vapor and total air in a cloud of moist air. Specific humidity cannot be affected by pressure change, so it is commonly used to characterize and calculate atmospheric water vapor content [4,5,6,7,8,9]. Analyzing tropospheric specific humidity is beneficial for deepening the knowledge of climate change, providing a foundation for analyzing regional water vapor content, water vapor budget, and other factors, as well as providing a basis for coping with regional climate change and improving the accuracy of forecasting and early warning
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