Saharan dust impact on radiative heating rate errors inherent in reanalysis data in the African easterly wave development region

Abstract

This study thoroughly examines the impact of aerosols on atmospheric heating rates over the North Atlantic Ocean, with a specific focus on developing African easterly waves (AEWs). The analysis leverages data from the National Aeronautics and Space Administration (NASA) DC-8 aircraft, dropsonde profiles, lidar observations, and satellite-based precipitation data obtained during NASA's Convective Processes Experiment – Cabo Verde (CPEX-CV) field campaign, as well as the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) and Copernicus Atmosphere Monitoring Service (CAMS) reanalyses. Using a four-stream radiative transfer model, the research specifically focuses on days characterized by Saharan dust coinciding with a developing AEW and contrasts its findings with a notable dust-only event in June 2020. The findings reveal notable differences in shortwave (SW) heating rates of over 1.5 K d−1 between reanalysis and observations, underlining the persistent challenges in accurately representing aerosol effects in the atmosphere, even after assimilating observational data. These discrepancies were present on days with both background and high dust concentrations, emphasizing the challenges in accurately representing aerosol radiative effects in models and highlighting the urgent need for improved aerosol representation in reanalysis datasets. Differences in heating rates were analyzed in a case study of two developing AEWs, one leading to a Category 4 hurricane (Fiona) and another leading to a short-lived tropical storm (TS; Hermine).