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Preprints
https://doi.org/10.5194/amt-2024-121
https://doi.org/10.5194/amt-2024-121
01 Aug 2024
 | 01 Aug 2024
Status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Synergy of active and passive airborne observations for heating rates calculation during the AEROCLO-SA field campaign in Namibia

Mégane Ventura, Fabien Waquet, Isabelle Chiapello, Gérard Brogniez, Frédéric Parol, Frédérique Auriol, Rodrigue Loisil, Cyril Delegove, Luc Blarel, Oleg Dubovik, Marc Mallet, Cyrille Flamant, and Paola Formenti

Abstract. Aerosols have important effects on both local and global climate, as well as on clouds and precipitations. We present some original results of the airborne AErosol RadiatiOn and CLOud in Southern Africa (AEROCLO-sA) field campaign led in Namibia in August and September 2017. In order to quantify the aerosols radiative impact on the Namibian regional radiative budget, we use an innovative approach that combines the OSIRIS polarimeter and lidar data to derive heating rate of the aerosols. To calculate this parameter, we use a radiative transfer code and meteorological parameters provided by dropsondes. This approach is evaluated during massive transports of biomass burning particles above clouds. We present vertical profiles of heating rates computed in the solar and thermal parts of the spectrum. Our results indicated strong positive heating rate values retrieved above clouds due to aerosols, between +2 and +5 Kelvin per day (vertically averaged). Within the smoke layer, water vapor's cooling effect through infrared radiation generally balances its warming effect from solar radiation. At the top of the layer, a stronger cooling effect of −1.5 K/day often dominates due to water vapor. In order to validate this methodology, we use irradiance measurements acquired during sounding performed with the aircraft during dedicated parts of the flights, which provides direct measurements of irradiances distribution and heating rates in function of the altitude. Finally, we discuss the possibility to apply this method to available and future spaceborne passive and active sensors.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Measurement Techniques. Moreover, Paola Formenti is guest editor for the ACP Special Issue “New observations and related modelling studies of the aerosol–cloud–climate system in the Southeast Atlantic and southern Africa regions”. The remaining authors declare that they have no conflicts of interests.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Short summary
Biomass burning aerosols (BBA) from Central Africa, are transported above stratocumulus clouds....
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