Abstract
The vertical structure of water vapor content in the atmosphere strongly affects the amount of solar radiation reaching the Earth’s surface and processes associated with the formation of clouds and atmospheric precipitation. The purpose of this study was to assess the vertical differentiation of water vapor over Europe on a seasonal basis and also to evaluate the role of atmospheric circulation in changes therein. Daily values of specific humidity (SHUM) for the time period 1981–2015 were obtained from pressure levels available from ECMWF Era-Interim reanalysis data and used in the study. Eight grid points were analyzed in detail. Each point is representative of a region with different moisture conditions. SHUM profiles were then used to identify cases of moisture inversion. Horizontal flux of specific humidity (SHUMF) was analyzed for principal pressure levels that occur in both inversion-type and inversion-free situations. In addition, SHUM and SHUMF anomalies were identified for advection directions. The research results showed the existence of differences in the vertical structure of water vapor content in the troposphere over Europe, and the Northeastern Atlantic and the presence of moisture inversions not only in areas north of 60°N but also in temperate and subtropical zones. Inversions can occur in two different forms—surface-based and elevated. The occurrence of inversions varies with the seasons. The role of atmospheric circulation is observable in the winter and triggers both surpluses and shortages of moisture via the effect of specific pressure system types (significant role of seasonal pressure high) and via advection directions. In addition, there exists a clear difference between the structure of moisture in the atmospheric boundary layer and in the free atmosphere.
Highlights
Academic Editor: Stefania Bonafoni e vertical structure of water vapor content in the atmosphere strongly affects the amount of solar radiation reaching the Earth’s surface and processes associated with the formation of clouds and atmospheric precipitation. e purpose of this study was to assess the vertical differentiation of water vapor over Europe on a seasonal basis and to evaluate the role of atmospheric circulation in changes therein
A large in ux of solar energy along with strong air temperature inversions, cloud cover that is sensitive to multiple factors, and mesoscale circulation determining moisture transport through meridional in ows cause large di erences in water vapor content across geographic space and in the vertical pro le in polar areas. is subject is examined in multiple studies that emphasize the importance of the vertical structure of water vapor content in energy balances [9, 10]
Water vapor content in the air varies over time and across geographic space, which is closely linked with changes in temperature conditions. e relationship between air temperature and water vapor pressure is described by the Clausius–Clapeyron equation
Summary
Received 28 November 2017; Revised 8 May 2018; Accepted 7 June 2018; Published 12 July 2018. E complexity of relationships between air temperature and water vapor content affects the radiation balance and water circulation patterns For these very reasons, studies on the vertical structure of water vapor in the atmosphere, its variability over time, and differentiation across geographic space play a key role in the analysis of climate change including parametrization of climate models and weather forecasting [3, 4]. Ese studies show that given the signi cance of water vapor content in key atmospheric processes, detailed analysis of the vertical structure of water vapor content in Arctic and Antarctic areas may provide additional information on factors modifying changes in moisture content in the atmosphere. They are representative of latitudinal (50.25°N) and longitudinal (15.75°W, 20.25°E) cross sections of the study area manifesting the e ect of geographic
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