Publication Date:
2023-06-05
Description:
While biases in simulated Southern Ocean (SO) shortwave radiative fluxes have improved in CMIP6 compared to CMIP5 models, there are remaining concerns regarding SO mixed phase clouds due to their important role in the climate system. Recent modeling studies come to opposing conclusions as to whether ice nucleation (IN) has a strong impact on SO shortwave cloud forcing. This study aims to investigate these conflicting findings using modeling and observations.In this work, we have implemented a deterministic immersion freezing ice nucleating particle (INP) scheme that includes contributions from mineral dust and marine sources into the Community Earth System Model version 2 (CESM2). This deterministic INP scheme replicates SO INP observations in the marine boundary layer with important sensitivities to modeled dust aerosol aloft. Simulated top-of-atmosphere cloud properties were minimally influenced by changes to the INP scheme. We investigated contributions of simulated cloud microphysical processes to the mass and number budgets in SO cloud regimes in the CESM2. Cloud regimes are identified based on cloud optical depth and altitude from satellite observations and simulated clouds sampled using the CFMIP Observation Simulator Package (COSP). This cloud regime clustering analysis allows for an assessment of cloud aerosol-ice processes in specific cloud regimes in CESM2. Results from these model experiments and analyses reveal the extent to which INPs control ice formation in specific cloud regimes in CESM2 and will be discussed in the context of recent SO field campaign observations.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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