ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-14-9213-2014 Estimation of mineral dust long-wave radiative forcing: sensitivity study to particle properties and application to real cases in the region of Barcelona Sicard M. https://orcid.org/0000-0001-8287-9693 1 5 Bertolín S. 2 Mallet M. 3 Dubuisson P. 4 Comerón A. https://orcid.org/0000-0001-6886-3679 2 RSLab/IEEC-CRAE, Universitat Politècnica de Catalunya, Barcelona, Spain RSLab, Universitat Politècnica de Catalunya, Barcelona, Spain Laboratoire d'Aérologie, Université de Toulouse/CNRS, Toulouse, France Laboratoire d'Optique Atmosphérique, Université Lille 1, Villeneuve d'Ascq, France on leave at: Laboratoire d'Aérologie, Université de Toulouse/CNRS, Toulouse, France 08 09 2014 14 17 9213 9231 Copyright: © 2014 M. Sicard et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/articles/14/9213/2014/acp-14-9213-2014.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/14/9213/2014/acp-14-9213-2014.pdf

The aerosol radiative effect in the long-wave (LW) spectral range is sometimes not taken into account in atmospheric aerosol forcing studies at local scale because the LW aerosol effect is assumed to be negligible. At regional and global scale this effect is partially taken into account: aerosol absorption is taken into account but scattering is still neglected. However, aerosols with strong absorbing and scattering properties in the LW region, like mineral dust, can have a non-negligible radiative effect in the LW spectral range (both at surface and top of the atmosphere) which can counteract their cooling effect occurring in the short-wave spectral range. The first objective of this research is to perform a sensitivity study of mineral dust LW radiative forcing (RF) as a function of dust microphysical and optical properties using an accurate radiative transfer model which can compute vertically resolved short-wave and long-wave aerosol RF. Radiative forcing simulations in the LW range have shown an important sensitivity to the following parameters: aerosol load, radius of the coarse mode, refractive index, aerosol vertical distribution, surface temperature and surface albedo. The scattering effect has been estimated to contribute to the LW RF up to 18% at the surface and up to 38% at the top of the atmosphere. The second objective is the estimation of the short-wave and long-wave dust RF for 11 dust outbreaks observed in Barcelona. At the surface, the LW RF varies between +2.8 and +10.2 W m<sup>−2</sup>, which represents between 11 and 26% (with opposite sign) of the SW component, while at the top of the atmosphere the LW RF varies between +0.6 and +5.8 W m<sup>−2</sup>, which represents between 6 and 26% (with opposite sign) of the SW component.

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