Solar Radiation and Heating Rates Under Desert Dust Conditions Based on Ground-Based Measurements and Simulations

Dust particles in the atmosphere alter the solar radiation field and Earth's energy budget, affecting climate (IPCC, 2022). Moreover, they may also change the thermodynamic properties of the atmosphere through radiative heating and/or cooling. The quantification of their direct radiative effects and heating rates (HRs) is crucial, however, the difficulty in defining their microphysical and optical properties as well as their high spatial and temporal variability make this quantification challenging. In the present study we focus on the evaluation of the impact of dust particles on the incoming solar irradiance and the vertical distribution of heating rates by performing closure studies for dust cases during the ASKOS ESA experiment in Cabo Verde. To this end, we adopt realistic particle shapes and their intrinsic microphysical and optical properties. The under-study period (summer of 2022) coincides with the annual peak of dust transport in the region. The study utilizes sophisticated ground-based remote sensing, airborne in-situ measurements, along with ground-based solar irradiance measurements and airborne observations of temperature profiles. More specifically, in order to derive realistic optical properties for dust particles in the atmosphere we combine UAV measurements of (ambient) dust size distribution, shape distribution and chemical composition, which provides information for the particle refractive index, with state-of-the-art scattering calculations and datasets. We perform radiative transfer (RT) simulations under clear and cloudy sky conditions employing the libRadtran RT package (Mayer & Kylling, 2005; Emde et al., 2016), in order to reproduce the ground-based broadband shortwave radiation measurements and the changes in the temperature profile of the atmosphere due to the induced heating from dust particles. This study provides valuable information of the dust radiative effects and corresponding HRs through a unique dataset of synergistic high-quality measurements. In spite of considerable progress in recent years regarding this topic, sophisticated atmospheric field experiments that provide highly accurate information are essential, not only to enrich knowledge, but for the validation and the improvement of ongoing and future satellite-based products as well.