Air Mass Patterns for Deep Convective Clouds over Poland in the first and second generation Meteosat retrievals

Deep Convective Clouds (DCCs) are associated with severe weather, where ‘severity’ refers to the potential negative impact of weather systems on human safety and the economy. As a natural hazard, convective storms need to be incorporated into mitigation plans, which is particularly important for mid-latitudes. Additionally, in a warming climate, extreme events are expected to occur more frequently. Motivated by the lack of DCC-focused air mass studies, this work evaluates how changes in circulation (air mass location and transport) relate to DCC activity over Poland.

The two generations of Meteosat observations provide a unique data record for studying the atmosphere and climate variability over Europe since the 1980s. Meteosat data enable the detection and, in a basic form, the tracking of DCCs, but the monitoring is limited to the lifetime of DCCs. While Meteosat data allow for the tracking of DCCs to some extent, identifying and following the air mass associated with their formation is not feasible using Meteosat data alone. One approach to overcoming this obstacle is to track air parcel transport in the atmosphere—i.e., calculating air parcel trajectories.

In this research, we identify cases of Deep Convective Clouds over Poland using the bi-spectral threshold method for DCC detection, which assesses differences in Brightness Temperature (BT) between infrared and water vapor channels. Our analysis is based on Meteosat Visible Infra-Red Imager (MVIRI) and Spinning Enhanced Visible Infra-Red Imager (SEVIRI) retrievals from the summer season of 2005. Thereafter, for each observation time, we determine which cells of a 0.25°×0.25° grid over Poland can be classified as having DCCs present and calculate the backward trajectory of the air mass for the center of each grid cell. For tracking purposes, we use the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, a widely recognized tool developed by the National Oceanic and Atmospheric Administration (NOAA) Air Resources Laboratory. The study examines air mass patterns associated with deep convective clouds forming over Poland and addresses the question: What are the dominant air mass sources and transport pathways leading to the formation of DCCs over Poland?

This research was funded by the National Science Centre of Poland. Grant no. UMO-2023/49/N/ST10/00366.