Evaluation of the accuracy of calculating the net shortwave radiation and air temperature in the ICON model in cloudless conditions.

We present the results of the inclusion of CAMS aerosol climatology (Bozzo et al., 2020) in the ICON mesoscale model (Giorgetta et al., 2018). The main differences between CAMS and Tegen aerosol climatology for AERONET stations (Holben et al., 1998) in Europe have been identified. Differences in aerosol content in climatology lead to significant changes in the calculation of the net shortwave radiation and meteorological elements. Thus, temperature changes can occur in almost the entire troposphere and can reach -1 °C up to heights of 350 gPa. At the same time, as the altitude increases, the sensitivity of air temperature changes decreases from 0.9±0.2 °C per 100 W/m2 per 1000 hPa, to 0.6±0.3 °C per 100 W/m2 at 950 hPa and to 0.1±0.3 °C per 100 W/m2 at 850 hPa. When calculating for longer periods of advance, the role of choosing aerosol climatology increases, especially for clear conditions. Thus, it was found that the difference in surface air temperature between the Tegen (Tegen et al., 1997) and CAMS experiments increases by 0.6 °C over 100 forecast hours. The key result of the work is an assessment of changes in the accuracy of calculating total radiation and meteorological elements compared with ground-based measurements. It was found that the choice of aerosol climatology is extremely important for the accuracy of calculating the net shortwave radiation at the earth's surface. The use of CAMS climatology significantly reduces the difference between calculations and measurements of net shortwave radiation compared to Tanre climatology (by an average of 37.5 W/m2). A decrease in the difference was also revealed when comparing with Tegen climatology (by an average of 4.7 W/m2). The use of CAMS climatology can improve the accuracy of forecasting surface air temperature to 0.3–0.4 °C for various meteorological stations compared to Tanre and Tegen climatology. An improvement in the temperature forecast is also noted at an altitude of 850 hPa (up to 0.2 °C), as well as for the amount of precipitation for the territory of the ETR.

Calculations based on the ICON configuration, designed for operational weather forecasting, were performed as part of the research work of Roshydromet 125032004255-7. The analysis of the radiation effects of aerosols was carried out with the financial support of the Russian Science Foundation grant No. 23-77-01030.

1. Bozzo A. et al. An aerosol climatology for global models based on the tropospheric aerosol scheme in the Integrated Forecasting System of ECMWF //Geoscientific Model Development. – 2020. – Т. 13. – №. 3. – С. 1007-1034.
2. Holben B. N. et al. AERONET—A federated instrument network and data archive for aerosol characterization //Remote sensing of environment. – 1998. – Т. 66. – №. 1. – С. 1-16.
3.  Tegen I. et al. Contribution of different aerosol species to the global aerosol extinction optical thickness: Estimates from model results //Journal of Geophysical Research: Atmospheres. – 1997. – Т. 102. – №. D20. – С. 23895-23915
4. Giorgetta M. A. et al. ICON‐A, the atmosphere component of the ICON earth system model: I. Model description //Journal of Advances in Modeling Earth Systems. – 2018. – Т. 10. – №. 7. – С. 1613-1637.