Observed Cloud Type‐Sorted Cloud Property and Radiative Flux Changes With the Degree of Convective Aggregation From CERES Data

• Published in: Journal of geophysical research. Atmospheres 2023-10, Vol.128 (19)
• Main Authors: Xu, Kuan‐Man, Zhou, Yaping, Sun, Moguo, Kato, Seiji, Hu, Yongxiang
• Format: Article
• Language: English
• Subjects: Aggregation; Climate; Climate and weather; Climate models; Cloud properties; Cloud types; Clouds; Geophysics; I.R. radiation; Infrared radiation; Low clouds; Meteorological conditions; Radiation-cloud interactions; Radiative cooling; Rain; Rainstorms; Satellite data; Satellites; Solar radiation; Subgroups; Thermal radiation; Weather
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2023JD039152

Cloud‐radiation interactions are a critical mechanism for convective self‐aggregation, especially the longwave radiative cooling of low clouds and environments. In this study, two data products from CERES observations combined with MERRA‐2 reanalysis are used to understand the changes of cloud properties and radiative fluxes by cloud type with the degree of convective aggregation at the 1000‐km scale, which is represented by the number of cloud objects ( N ), simple convective aggregation index (SCAI), modified SCAI (MCAI) or convective organization potential (COP). The changes with SCAI are similar to those with N as an index, agreeing with previous studies using grid‐averaged properties. For changes from weak to strong degrees of aggregation using N and SCAI, area fractions of middle‐ and high‐level cloud types decrease by up to 4% but those of low‐level cloud types increase by up to 2%, and more infrared radiation is emitted to space (2–8 W m −2 ) from optically thin cloud types but more solar radiation is reflected (2–4 W m −2 ) from optically‐thick cloud types. However, using COP (MCAI to lesser extent), area fractions of optically‐thick cloud types increase, which emit less infrared radiation and reflect more solar radiation, whereas the area fractions of low‐level clouds decrease. These results can be explained by greater expansion of cloud object sizes for COP than MCAI/SCAI as the degree of convective aggregation increases, which also explains the difference between SCAI and MCAI pertaining to the opposite changes of optically‐thick high‐level clouds. These results can have implications for understanding convective self‐aggregation. Rainstorms are often clustered in ways that depend upon meteorological conditions; this is known as “convective aggregation.” The amount of aggregation has a large influence on both weather and climate, so being able to understand how the properties of rainstorms change with the strength of convective aggregation is important for weather and climate modeling. Previous studies used satellite data that only characterized the cold and deep parts of rainstorms. This study provides an analysis of 42 cloud types using the latest satellite data. We assess the changes of cloud area coverage, solar radiation and thermal radiation between two subgroups of data samples with vastly different strengths of aggregation. We find that two of four aggregation measures produce nearly identical changes for cloud area coverages of low‐ and