Parameterizing the optical properties of carbonaceous aerosols in the Canadian Centre for Climate Modeling and Analysis Atmospheric General Circulation Model with impacts on global radiation and energy fluxes

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Abstract

[1] Parameterizations of the optical properties of black carbon (BC) and organic carbon (OC) aerosols in an external mixture are presented. The parameterizations in terms of look-up tables are based on exact Mie calculations for a high number of wavelengths and values of the relative humidity. Both the shortwave, and the longwave portions of the atmospheric radiation spectra are considered. The parameterizations are used in the developmental version of the fourth generation Canadian Centre for Climate Modelling and Analysis (CCCma) Atmospheric General Circulation Model (AGCM). Previously, this model neglected the impact of OC and BC on the radiative fluxes. The effect of OC and BC on global radiation and energy fluxes is quantified and compared to other aerosol types. It is found that the fraction of the OC/BC aerosol direct effect is rather high. The OC/BC aerosol is responsible for 25% to 65% of the absolute value of the total direct aerosol effect on various radiation and energy fluxes. At the top of the atmosphere, the change in the net solar flux due to BC and OC is +0.31 W m−2, but the sum of all aerosols except for nitrate but including BC and OC leads to a decrease in the net solar flux of 1.16 W m−2. The sum of all aerosols without nitrate reduces the surface sensible heat flux by 0.84 W m−2 with a BC/OC fraction of 0.55 W m−2. For the surface latent heat flux, these values are 1.05 W m−2 and 0.50 W m−2, respectively.

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