Direct and semi-direct radiative forcing of biomass-burning aerosols over the southeast Atlantic (SEA) and its sensitivity to absorbing properties: a regional climate modeling study

Atmospheric chemistry and physics

article

Mallet, Marc¹  Michou, Martine¹  Zuidema, Paquita²  Flamant, Cyrille³  Redemann, Jens⁴  Formenti, Paola⁵  Solmon, Fabien⁶  Nabat, Pierre¹  Elguindi, Nellie⁶  Waquet, Fabien⁷  Bouniol, Dominique¹  Sayer, Andrew Mark⁸  Meyer, Kerry⁹  Roehrig, Romain¹ 

[1] Centre National de Recherches Météorologiques;Rosenstiel School of Marine and Atmospheric Sciences, University of Miami;Sorbonne Université;School of Meteorology, University of Oklahoma;Université Paris Est Créteil et Université Paris Diderot, Institut Pierre Simon Laplace;Laboratoire d'Aérologie;Université de Lille, LOA – Laboratoire d'Optique Atmosphérique;Universities Space Research Association Columbia;NASA Goddard Space Flight Center

DOI  :  10.5194/acp-20-13191-2020

学科分类：医学（综合）

来源: Copernicus Publications

【 摘 要 】

Simulations are performed for the period 2000–2015 by two different regional climate models, ALADIN and RegCM, to quantify the direct and semi-direct radiative effects of biomass-burning aerosols (BBAs) in the southeast Atlantic (SEA) region. Different simulations have been performed using strongly absorbing BBAs in accordance with recent in situ observations over the SEA. For the July–August–September (JAS) season, the single scattering albedo (SSA) and total aerosol optical depth (AOD) simulated by the ALADIN and RegCM models are consistent with the MACv2 climatology and MERRA-2 and CAMS-RA reanalyses near the biomass-burning emission sources. However, the above-cloud AOD is slightly underestimated compared to satellite (MODIS and POLDER) data during the transport over the SEA. The direct radiative effect exerted at the continental and oceanic surfaces by BBAs is significant in both models and the radiative effects at the top of the atmosphere indicate a remarkable regional contrast over SEA (in all-sky conditions), with a cooling (warming) north (south) of 10  ∘ S, which is in agreement with the recent MACv2 climatology. In addition, the two models indicate that BBAs are responsible for an important shortwave radiative heating of ∼0.5 –1 K per day over SEA during JAS with maxima between 2 and 4 km a.m.s.l. (above mean sea level). At these altitudes, BBAs increase air temperature by ∼0.2 –0.5 K, with the highest values being co-located with low stratocumulus clouds. Vertical changes in air temperature limit the subsidence of air mass over SEA, creating a cyclonic anomaly. The opposite effect is simulated over the continent due to the increase in lower troposphere stability. The BBA semi-direct effect on the lower troposphere circulation is found to be consistent between the two models. Changes in the cloud fraction are moderate in response to the presence of smoke, and the models differ over the Gulf of Guinea. Finally, the results indicate an important sensitivity of the direct and semi-direct effects to the absorbing properties of BBAs. Over the stratocumulus (Sc) region, DRE varies from +0.94  W m −2 (scattering BBAs) to +3.93  W m −2 (most absorbing BBAs).

【 授权许可】

CC BY