Characteristics of warm clouds under the Köppen climate classification system with contoured frequency by optical depth diagrams

Abstract

This study investigates the impact of atmospheric factors such as humidity, temperature, and aerosol properties on the growth and internal structure of warm clouds, focusing on variations in cloud optical depth (COD) and cloud droplet effective radius (CDR). Using satellite data from Aqua's Moderate Resolution Imaging Spectroradiometer and CloudSat's Cloud Profiling Radar (2006–2014), the study employs Contoured Frequency by Optical Depth Diagrams (CFODD) to analyze cloud evolution as CDR increases. The Köppen climate classification is applied to assess how atmospheric conditions influence warm cloud characteristics. The study finds that regions with similar climates exhibit comparable cloud behaviors. In tropical regions, cloud droplet mode dominates at CDR values between 6 and 15 μm, transitioning to rain as CDR exceeds 15 μm. In arid regions, limited moisture availability results in thinner warm clouds, a smaller CDR range, and fast cloud dissipation. Temperate and continental regions exhibit slower transitions from cloud droplet mode to drizzle and rain, with CDR exceeding 18 μm, while lower surface temperatures promote more drizzle formation. In polar regions, extremely low temperatures exacerbate these limitations by weakening turbulence and vertical motion, which further slow collision and coalescence processes, requiring a much larger CDR exceeding 21 μm for rain formation, with most precipitation occurring as drizzle.