Impact of climate change on ERA5 cloud cover and convective parameters in Central Europe (1983-2022)

In discussions about climate change, the focus is usually on rising temperatures. However, it is important to understand the significant impact of climate change on the entire weather system. The cloud feedback mechanism is one of the most complex factors in the climate system. This is because clouds can have a heating and cooling effect at the same time, and this balance has a significant influence on the global radiation balance. To understand how all the different factors work together to create a complex system, we need to look closely at how these factors have changed over time.

The aim of this research is to examine changes in cloud cover and convective parameters, as well as the background, causes and effects of these changes in Central Europe between 1983 and 2022. The research uses data from the ERA5 reanalysis database. Aside from the analysis of environmental conditions, an objective cyclone identifying method is used to determine regions under low- or high-pressure weather system influence.  

The statistical analysis shows that in general, the decrease in ERA5 low-level cloud cover is associated with an increase in cloud base. Medium- and high-level cloud cover, however, is influenced by changes in large-scale circulation systems.

Low-level cloud cover decrease in the northern regions of the study area is likely due to increasing temperatures and decreasing boundary layer humidity. Though temperatures in the Mediterranean region also have risen, the increase in the frequency of negative NAO situations, and an increase in Mediterranean cyclone and low-pressure system activity - the latter of which is likely induced by the higher evaporation of the Mediterranean Sea - resulted in the increase in cloud cover over the central Mediterranean region. We have also observed an increase in the CAPE (convective area pressure energy) in the Mediterranean during the summer months, which leads to an increase in the frequency of heavy thunderstorms and extreme precipitation events in this area, contributing to the intensification of weather extremes in the region. Changes over the study area are not linear but show a region dependent 10-20 years periodical pattern which is also investigated.