Publications

Sockol, A; Griswold, JDS (2017). Intercomparison between CMIP5 model and MODIS satellite-retrieved data of aerosol optical depth, cloud fraction, and cloud-aerosol interactions. EARTH AND SPACE SCIENCE, 4(8), 485-505.

Abstract
Aerosols are a critical component of the Earth's atmosphere and can affect the climate of the Earth through their interactions with solar radiation and clouds. Cloud fraction (CF) and aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used with analogous cloud and aerosol properties from Historical Phase 5 of the Coupled Model Intercomparison Project (CMIP5) model runs that explicitly include anthropogenic aerosols and parameterized cloud-aerosol interactions. The models underestimate AOD by approximately 15% and underestimate CF by approximately 10% overall on a global scale. A regional analysis is then used to evaluate model performance in two regions with known biomass burning activity and absorbing aerosol (South America (SAM) and South Africa (SAF)). In SAM, the models overestimate AOD by 4.8% and underestimate CF by 14%. In SAF, the models underestimate AOD by 35% and overestimate CF by 13.4%. Average annual cycles show that the monthly timing of AOD peaks closely match satellite data in both SAM and SAF for all except the Community Atmosphere Model 5 and Geophysical Fluid Dynamics Laboratory (GFDL) models. Monthly timing of CF peaks closely match for all models (except GFDL) for SAM and SAF. Sorting monthly averaged 2 degrees x 2.5 degrees model or MODIS CF as a function of AOD does not result in the previously observed "boomerang"-shaped CF versus AOD relationship characteristic of regions with absorbing aerosols from biomass burning. Cloud-aerosol interactions, as observed using daily (or higher) temporal resolution data, are not reproducible at the spatial or temporal resolution provided by the CMIP5 models. Plain Language Summary Aerosols, or suspended particles, are a critical component of the Earth's atmosphere and can affect the climate of the Earth through their interactions with solar radiation and clouds. To understand how aerosols impact clouds, measurements are made from space on satellites and simulated using global climate models. Here we compare the results of several global climate models that include explicit simulations of aerosol-cloud interactions with observations from satellites over the same time period (2000-2005). Seasonally, we find that the global climate models both underestimate and overestimate aerosols and clouds over different regions of the Earth. Looking at individual months, the models do a better job of estimating what months there should be more or less aerosols and aerosols. To further investigate how well models simulate the space-based measurements, we look at two regions (South America and South Africa) that are dominated by smoke aerosols. Using both the satellite and model data, we compared these regions and found that the models, which give information on a monthly time scale, are not detailed enough in time to see relationships that are usually seen on a daily time scale from space. Overall, for aerosol-cloud interactions to be simulated realistically models need to improve.

DOI:
10.1002/2017EA000288

ISSN:
2333-5084