Dynamics of key climate variables over Europe

Temperature and humidity are key climatic variables for the assessment of climate variability. This study focuses on the climatic trends of temperature, specific and relative humidity both at the surface and in multiple pressure levels in the atmosphere. We present the first results of the analysis the dynamics of some key climate variables over Europe. The analysis was conducted for Europe, but it is focusing also on Greece. The main purpose of this study is to investigate whether possible changes in the basic climate variables exist over the recent years. 

Data from the ERA5 reanalysis product are used for the period 1979-2018 (40 years) with spatial resolution of 0.25° x 0.25°. The Sen’s slope estimator is used to identify the climate trends at each grid point and the Mann-Kendall statistical test was applied to detect statistically significant spatial and temporal changes for the examined domain. The results indicate statistically significant warming trends at the 99% level over land and sea at surface. Regarding Greece, statistically significant warming trends at the 99% level occur during summer. In addition, positive temperature trends are also presented over land and sea, in the troposphere, over the particular domain. In contrast, in the stratosphere, statistically significant cooling trends at the 99% level are observed. Additionally, the stratospheric cooling trends increase with increasing altitude in the atmosphere. Regarding the climatic trends of the specific humidity, mainly positive values prevail up to mid-troposphere. Finally, the climatic trends of the relative humidity exhibit positive and negative values due to the relationship of humidity and temperature.