Modeling impacts of dust mineralogy on Earth’s Radiation and Climate
Abstract. Mineralogical composition drives diverse dust impacts on Earth’s climate. However, most climate models still use fixed dust mineralogy, neglecting its temporal and spatial variation. To quantify the radiative impact of resolving dust mineralogy on Earth’s climate, we simulate the distribution of dust minerals in the GFDL AM4.0 model. Resolving dust mineralogy reduces dust absorption and results in improved agreement with observation-based dust absorption, radiative fluxes, and land surface temperature. It leads to a reduction of over 50 % in net downward radiation across the Sahara and approximately 20 % over the Sahel at top of atmosphere (TOA) in JJA. The reduced dust absorption weakens the atmospheric warming effect and leads to a surface temperature decrease of 0.4 K over the Sahara and an increase of 0.6 K over the Sahel. The less warming in the atmosphere suppresses ascent and weakens the monsoon inflow from the Gulf of Guinea. This brings less moisture to the Sahel, which combined with decreased ascent induces a reduction of precipitation. Interestingly, we find similar results by simply fixing the dust hematite content to 0.9 % by volume, which is more computationally efficient. However, uncertainties related to emission and distribution of minerals may blur the advantages of resolving minerals to study their impact on radiation, cloud properties, ocean biogeochemistry, air quality, and photochemistry. On the other hand, lumping together clay minerals, excluding externally mixed hematite and gypsum, appears to provide both computational efficiency and relative accuracy. Nevertheless, for specific research, it may be necessary to fully resolve mineralogy to achieve accuracy.
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