Atmospheric water vapour distribution and moisture transport over Europe and their impact on the humidity conditions over Poland

The amount of atmospheric water vapour and its transport were analysed to rate the intensity and main directions of moisture fluxes incoming to Poland. The total column water vapour (TCWV) was used to show the total amount of water vapour in the entire atmosphere, whereas the specific humidity (SH) allow to show vertical variation of the moisture properties. Also, the SH fluxes were applied to verify the main directions of water vapour transport at the pressure level of 925 hPa, 850 hPa and 700 hPa over Europe. The Atlantic Ocean is the relevant source of water vapour, which is advected to Europe due to the western circulation dominant in mid-latitudes. Huge supplies of water vapour and higher wind speeds affect the strongest fluxes there. Thus, the strongest SH fluxes come from the west (the monthly mean in July is up to 61 g∙kg − 1 ∙m∙s − 1 in Lodz). It is also the most frequent direction of atmospheric water vapour supplies over Poland. Simultaneously, long-term trends in TCWV and SH are mostly insignificant. There is a slight increase in the amount of water vapour in the subpolar region in the colder half of the year, and over Central, Eastern and Northern Europe in summer. These results show that the increasing saturation deficit and more frequent dry events are not caused by the change in the amount of water vapour. This provides the ground for claiming that the drying of the atmosphere is affected mainly by increasing temperature.