The Temporal and Spatial Variability of Cloud Properties Over Poland Based on Satellite Data (2003–2021)

Abstract

Cloud cover is a key meteorological element that plays a crucial role in Earth's climate system and remains a significant source of uncertainty in climate estimations. Over recent decades, changes in the frequency of certain cloud types have been observed in Poland, including increases in high and convective clouds and a decrease in stratiform clouds. These trends underscore the need for detailed regional analyses of cloud properties. In this study, we present a comprehensive 19-year analysis of cloud top pressure (CTP), cloud optical thickness (COT), cloud effective radius (CER) and cloud water path (CWP). We investigate the Moderate Resolution Imaging Spectroradiometer (MODIS) Cloud Product Collection 6.1 Level 2 data from both the Terra and Aqua spacecraft, covering the period from 2003 to 2021. Our findings indicate that, over the past two decades, CTP over Poland has consistently decreased by 7.3–9.7 hPa per decade. This decline primarily affects northern and north-western Poland, with local decreases reaching up to −40.0 hPa per decade. High clouds (CTP < 440 hPa) exhibited the most pronounced changes, with a statistically significant negative trend observed over 25%–35% of the area of Poland. While area-averaged monthly means for cloud microphysical and optical characteristics did not change over the analysed period, a detailed investigation of clouds with different CTP or COT revealed additional phenomena. In particular, COT declined by 1.15–2.25 every 10 years for low-to-mid level cloud (CTP 560–800 hPa), CER and CWP decreased in cloud with COT < 9.4 during morning passes, and CER and CWP increased in cloud with COT ≥ 9.4 during afternoon passes. These findings are particularly important for understanding the radiative properties of clouds and their role in atmospheric energy balance.