Recent studies have identified several statistically significant trends in cloud genera frequency over Poland. Notably, there has been an increase in high and convective clouds, along with a decrease in Stratus, Altostratus and Nimbostratus. These earlier studies were, however, only based on traditional, surface data. As the ability to observe mid and high-level clouds from the ground is limited, due to overlapping, we address the question of whether these trends are confirmed by other sources of cloud data, such as satellite records. In this paper, we analyse cloud data from two fully independent sources to characterize the cloud type climatology over Poland for the period 2003–2021: cloud optical thickness (COT) and cloud top pressure (CTP) parameters retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS), and surface (SYNOP) observations of cloud genera from the country’s 27 ground-based stations. The International Satellite Cloud Climatology Project (ISCCP) COT–CTP classification was used to define MODIS cloud types. We explore the hypothesis that MODIS data, classified using the ISCCP philosophy, confirms the changes in cloud type frequencies found in SYNOP observations. Our analysis is based on the application of the Spearman rank correlation test to mean monthly SYNOP and MODIS cloud type frequencies, and we compare per decade trends for two time series. Our hypothesis was confirmed, but only for Cirrus, Altostratus + Nimbostratus and Cumulus. We therefore conclude that the two analysed data sources are not fully consistent, and cannot substitute for each other in cloud type climatologies. Hence, at least for Poland, they should be treated as independent rather than complementary. We also demonstrate that the increase in high-level cloud frequency over Poland, which has been observed by other authors who based their research on synoptic data, is not due to a decrease in the frequency of low- and mid-level clouds. Our findings are confirmed by satellite records.
Wojciechowska, I., Kotarba, A. Z., & Żmudzka, E. (2023). Cloud type frequency over Poland (2003–2021) revealed by independent satellite-based (MODIS) and surface-based (SYNOP) observations. International Journal of Climatology, 1– 19.