Heterogeneous ice nucleation in the WRF-Chem 3.9.1.1 model and its influence on cloudresponse to volcanic aerosols

• Main Authors: Marelle, Louis, Myhre, G., Raut, Jean-Christophe, Keita, Seitigi Aboubacar
• Other Authors: TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Center for International Climate and Environmental Research Oslo (CICERO), University of Oslo (UiO), Centre ESCER, Université du Québec à Montréal = University of Québec in Montréal (UQAM)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2021
• Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Holuhraun; Iceland
• Online Access: https://insu.hal.science/insu-03745758

International audience Heterogeneous ice formation on aerosols is the main primary cloud ice formation process above temperatures of -38°C, and asa consequence it plays a major role in the formation of mixed-phase and ice clouds. Improving our understanding of iceprocesses could help better constrain the radiative forcing of cloud aerosol interactions, which remains a major source ofuncertainty in climate projections. Despite their importance, most atmospheric models do not represent aerosol-cloud iceprocesses explicitly.We extend in the WRF-Chem 3.9.1 model a recent parameterization of deposition-mode ice nucleation to also includeimmersion-mode nucleation, based on the classical nucleation theory (CNT) description. We also couple this parameterizationwith the aerosol-liquid cloud parameterization of Abdul Razzak and Ghan already included in WRF-Chem 3.9.1. This allows us tomodel the effect of aerosols on mixed-phase and ice clouds. We use volcanic eruptions as case studies, especially focusing onthe 2014/2015 Holuhraun/Bárðarbunga eruption in Iceland. Specifically, we investigate how volcanic aerosols influencemodeled cloud microphysical properties with and without the explicit ice nucleation parameterization, comparing the modelagainst MODIS satellite observations. We also investigate the effect of these processes on the cloud response in terms ofoptical properties, radiative fluxes, and precipitation during the eruptions