Preprints
https://doi.org/10.5194/acp-2022-233
https://doi.org/10.5194/acp-2022-233
 
30 Mar 2022
30 Mar 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Acceleration of the southern African easterly jet driven by radiative effect of biomass burning aerosols and its impact on transport during AEROCLO-sA

Jean-Pierre Chaboureau1, Laurent Labbouz1, Cyrille Flamant2, and Alma Hodzic3 Jean-Pierre Chaboureau et al.
  • 1Laboratoire d’Aérologie (LAERO), Université de Toulouse, CNRS, UPS, Toulouse, France
  • 2LATMOS/IPSL, Sorbonne Université, CNRS, UVSQ, Paris, France
  • 3National Center for Atmospheric Research, Boulder, CO, USA

Abstract. The direct and semi-direct radiative effects of biomass burning aerosols (BBA) are investigated over southern Africa and the southeast Atlantic during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) field campaign in September 2017. A reference convection-permitting simulation has been performed using the Meso-NH model with an on-line dust emission scheme, a BBA tracer emitted using the daily Global Fire Emissions Database and online-computed backward Lagrangian trajectories. The simulation captures both the aerosol optical depth and the vertical distribution of aerosols as observed from airborne and space-borne lidars. It also reproduces the occurrence of stratocumulus over the southeast Atlantic, deep convective clouds over equatorial Africa and the large-scale circulation. In contrast, a sensitivity experiment where the radiative effect of BBA is not taken into account shows the smoke plume that is predicted too low in altitude, low-cloud cover that is too weak, deep convective activity that is too frequent but not intense enough, a Benguela jet that is too strong and a southern African easterly jet that is too weak. The Lagrangian analysis indicates that BBA are transported to higher altitudes, farther southwest and with a stronger diurnal oscillation when accounting of the radiative effects of BBA. The higher smoke plume altitude can be explained by a combination of three factors: increased upward motion induced by the stronger southern African easterly jet, self-lofting of BBA and reduced subsidence associated with a less frequent deep convective activity over equatorial Africa.

Jean-Pierre Chaboureau 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-2022-233', Anonymous Referee #1, 22 Apr 2022
  • RC2: 'Comment on acp-2022-233', Anonymous Referee #2, 22 Apr 2022

Jean-Pierre Chaboureau et al.

Jean-Pierre Chaboureau et al.

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Short summary
Ground-based, space-borne and rare airborne observations of biomass burning aerosols (BBA) during the AEROCLO-sA field campaign in 2017 are complemented with convection-permitting simulations with online trajectories. The results show that the radiative effect of the BBA accelerates the southern African easterly jet and generates upward motions that transport the BBAs to higher altitudes and farther southwest.
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