The Global Spatial and Temporal Distribution of Ice Cloud Optical Thickness Based on MODIS Satellite Data during 2000-2021

Ice cloud optical thickness (IOT) is an important parameter to characterize ice cloud properties and in the determination of cloud-radiation parameterization schemes, and the variation trend of ice clouds is more concerned with the study of weather and climate. In this paper, we analyzed the spatial and temporal distributions of IOT over the region between & PLUSMN;60 & DEG; latitude. Cloud product data from March 2000 to February 2021 acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Aqua satellite were used in this study. Theil-Sen median trend analysis and EOF analysis methods were used to study the variation trend of IOT. The research results indicate that the monthly average IOT shows a "W" distribution from January to December, with a maximum reached in July (12.15) and a double bottom reached in March (10.7) and October (10.99), respectively. The average global IOT reaches the maximum in June-August, it tends to decrease with time, and its slope is -0.01 year(-1). The statistical analysis results show that the area with an increase accounted for 49.4% of the total ice cloud coverage area; the area with a trend of significant increased and decreased is both 2.2%. The probability distribution of IOT reaches the maximum, around 3.25%, when the IOT is larger than 1.5 and less than or equal to 2.