Radiation in the atmosphere provides the energy that drives atmospheric dynamics and physics on all scales, from cloud particle growth to global weather and climate. Radiation schemes in global weather and climate models make assumptions to simplify the complex interaction of radiation with the Earth system. Capturing cloud-radiation interactions is particularly challenging since clouds vary strongly on small spatial and temporal scales not resolved in the models, and interact strongly with radiation. Uncertainties in these assumptions in the radiation scheme and the cloud, aerosol, gas and surface inputs lead to uncertainties in multiple weather and climate processes, such as energy balance, cloud development and dynamics.
The modular radiation scheme ecRad (Hogan and Bozzo, 2018, Rieger et al. 2019) is operational in ICON at DWD since April 2021 and provides the opportunity to vary parametrisations and assumptions individually to determine their impact. Several options are available for the radiation solver, cloud vertical overlap and horizontal inhomogeneity treatment and cloud hydrometeor optical property parametrisations. The solver SPARTACUS is the only radiation solver in a global model that can treat 3D radiative effects.
Using global satellite and surface data and high-resolution surface radiation measurements gathered during the FESSTVaL campaign (https://fesstval.de), we evaluate the radiation and cloud parametrisations on local to global scales and investigate the sensitivity of radiation results to model assumptions and cloud properties and the role of cloud-radiation interactions. In ICON, ecRad improves the global radiation balance, model physics and forecast performance as evaluated against observations.
References:
Hogan, R. J., & Bozzo, A. (2018), A flexible and efficient radiation scheme for the ECMWF model. Journal of Advances in Modeling Earth Systems, 10, 1990-2008. https://doi.org/10.1029/2018MS001364
Rieger, Daniel, Martin Köhler, Robin J. Hogan, Sophia A. K. Schäfer, Axel Seifert, Alberto de Lozar and Günther Zängl (2019). ecRad in ICON - Implementation Overview, Reports on ICON
How to cite: Schäfer, S., Köhler, M., Hogan, R., Ahlgrimm, M., Rieger, D., Schlemmer, L., Sakradzija, M., Mol, W., van Heerwarden, C., and Jakub, F.: Radiation and cloud parametrisation in ICON on local to global scales, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-632, https://doi.org/10.5194/ems2022-632, 2022.
