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

Abstract

Saharan dust outbreaks strongly impact the atmosphere’s energy balance, as their radiative effects can alter atmospheric heating rates by several degrees per day. However, numerical weather prediction models often struggle to accurately represent aerosol vertical distribution, leading to forecast errors driven by biases in heating rates. Utilizing a four-stream radiative transfer model and data from reanalysis as well as dropsonde profiles and lidar observations from NASA’s CPEX-CV field campaign, this study examines the impact of Saharan dust on atmospheric heating rates over the North Atlantic Ocean, with a specific focus on the African Easterly Wave (AEW) development region. The performance of two reanalyses, MERRA-2 and CAMS, is evaluated, and results reveal notable differences in aerosol-induced shortwave heating of over 1.5 K/day between reanalysis and field observations. These findings underline the persistent challenges in accurately representing aerosol effects in the atmosphere, even after the assimilation of observational data. A case study of three developing AEWs during the CPEX-CV field campaign highlights a difference in aerosol-induced heating on the order of 1 to 2 K/day between two AEWs developing into major hurricanes and one developing into a short-lived tropical storm, raising the question of the role of dust-induced heating in AEW development.