21 Jul 2021

21 Jul 2021

Review status: a revised version of this preprint is currently under review for the journal ACP.

Effects of Saharan Dust on African Easterly Waves: The Impact of Aerosol-Affected Satellite Radiances on Data Assimilation

Dustin Francis Phillip Grogan1, Cheng-Hsuan Lu1,2, Shih-Wei Wei1, and Sheng-Po Chen1,3 Dustin Francis Phillip Grogan et al.
  • 1University at Albany, State University of New York, Albany, NY
  • 2Joint Center for Satellite Data Assimilation, Boulder, CO
  • 3Department of Chemistry, National Central University, Taoyuan, Taiwan

Abstract. This study incorporates time-varying aerosols into satellite radiance calculations within the Global Data Assimilation System (GDAS) to investigate its impact on African easterly waves (AEWs) and their environment. Comparison of analysis fields from the aerosol-aware experiment and an aerosol-blind control during August 2017 showed that the aerosol-affected radiances accelerated the African easterly jet and West African monsoon flow; warmed the Saharan boundary layer; and modified the AEW vorticity structure, with increases in the northern circulation and decreases in the southern circulation. Analysis fields from each experiment were used in the Global Forecast System (GFS) to examine differences in forecasting two AEW cases that developed hurricanes over the Atlantic, but were structurally different over North Africa. The aerosol-aware experiment reduced errors in forecasting the AEW case whose northern circulation interacted with a large-scale Saharan dust plume; neutral improvement was found for the other AEW, which did not contain a northern circulation nor interacted with a dust plume.

The changes to the analysis fields by the aerosol-aware assimilation are reminiscent of dust radiative effects that operate on AEWs and their environment. That is, the aerosol-affected radiances produce corrections to the brightness temperatures that modify the analysis fields like dust aerosols that are radiatively coupled to the atmospheric variables in the forecast model. We show qualitatively that dust radiative effects are captured by the aerosol-affected radiances for the AEW case that interacted with a dust plume, which served to improve forecasts of the wave downstream.

Dustin Francis Phillip Grogan et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-129', Anonymous Referee #1, 02 Aug 2021
    • AC1: 'Reply on RC1', Dustin Grogan, 14 Oct 2021
  • RC2: 'Comment on acp-2021-129', Anonymous Referee #2, 06 Aug 2021
    • AC2: 'Reply on RC2', Dustin Grogan, 14 Oct 2021
  • RC3: 'Comment on acp-2021-129', Anonymous Referee #3, 07 Aug 2021
    • AC3: 'Reply on RC3', Dustin Grogan, 14 Oct 2021

Dustin Francis Phillip Grogan et al.

Dustin Francis Phillip Grogan et al.


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Short summary
This study shows that incorporating aerosols into satellite radiance calculations affects the representation of African easterly waves (AEWs), and their environment, over North Africa and the East Atlantic in a numerical weather model. These changes are driven by radiative effects of Saharan dust captured by the aerosol-affected radiances, which modify the initial fields and can improve the forecasting of AEWs.