Simulations with a multiscale climate model that permits boundary-layer eddies suggest a weaker aerosol-cloud interaction
Abstract
We present results from global simulations using the multi-scale climate model (Ultra-Parameterized Community Atmosphere Model - UPCAM), which has the unique feature of resolving scales that permit explicit treatment of large boundary layer eddies. These results are the first instance where the aerosol-cloud interaction is studied using a global model that explicitly treats boundary layer turbulence. The high resolution of the embedded model in UPCAM allows for realistic cloud droplet number nucleation of aerosols without relying on parameterizations of boundary layer turbulence. When the UPCAM simulations are compared to those from the multi-scale Super-Parameterized Community Atmosphere Model (SPCAM) and traditionally parameterized Community Atmosphere Model version 5.3 (CAM5.3), we find a weaker aerosol-cloud interaction (ACI) in UPCAM.
The weaker ACI stems from a weaker increase in cloud liquid water path with increasing aerosol concentrations. Consistent with previous studies of SPCAM and CAM5, model process-oriented diagnostics suggest that the increase in liquid water path in UPCAM is driven by a suppression of precipitation (cloud lifetime effect). We hypothesize and present evidence that the weaker increase in liquid water path stems from a lower probability of precipitation in UPCAM, compared to CAM5 or SPCAM, which means that a smaller fraction of the cloud population in UPCAM can participate in the cloud lifetime effect.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A13E..03T
- Keywords:
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- 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSES