Cloud radiative effects due to deep convective clouds in the tropics: Insights from Himawari-8 observations

Understanding Earth’s equilibrium sensitivity remains one of the key challenges of climate science, with cloud feedbacks representing a major source of uncertainty. High clouds associated with deep convective systems in the tropics have been shown to make a large contribution to this uncertainty. With a goal of improving our understanding of radiative properties of tropical high clouds, we investigate cloud radiative effects (CREs) of high clouds within mesoscale convective systems (MCSs) in the tropical western Pacific. The study uses a novel high-resolution (3-km), hourly dataset derived from the advanced Himawari imager onboard the Himawari-8 satellite. Cloud properties are retrieved with Optimal Retrieval of Aerosol and Cloud (ORAC) and the top-of-the-atmosphere CREs are calculated using the Broadband and Narrowband Radiative Transfer Model (BUGSrad). We identify and track MCSs during 2018–2022 using 11.2 μm brightness‑temperature data with a 233 K threshold and a minimum cloud‑top area of 1000 km², employing the ‘simple-track’ cloud-tracking algorithm. The analysis shows that, on an average, larger storms have more negative net CRE than smaller storms. Moreover, shorter-lived storms have a net CRE close to zero. Results based on all tracked MCSs across the 3-year period indicate that MCSs have a net CRE of -12.80 W m-2, though there exists a negative bias in Himawari-derived net CRE (that stems from bias in shortwave CRE) when compared to CERES-EBAF dataset. Further analysis separates clouds into low-brightness-temperature and high-brightness-temperature regimes, and show how these two cloud regimes evolve throughout the 3-year period.