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The effects of sea ice and cloud variability on the top-of-atmosphere albedo
| PI: |
Irina Gorodetskaya |
| Institution: |
Columbia University |
| Additional Investigators: |
Bruno Tremblay, Beate Liepert, Mark Cane |
| Abstract: |
Objective: Coupled general circulation model output will be analyzed and compared to observations from satellites in order to understand how the top-of-atmosphere (TOA) albedo responds to sea ice concentration and cloud changes in the polar regions.
Background: Models show significant variations in the magnitude of the ice/snowalbedo feedback, which is thought to strongly amplify climate sensitivity in the polar regions. Sea ice retreat implies increased evaporation and thus can lead to increased cloud formation, though it is unclear how the clouds will actually respond as their formation depends not only on the local moisture budget but on synoptic patterns and the advection of heat and moisture. The simulation of these processes vary significantly among the models which is in part responsible for the contribution of clouds to the uncertainty in the ice-albedo feedback magnitude. The difficulty in estimating the effects of sea ice and clouds on radiation has been aggravated by lack of long and accurate data sets of the TOA radiative fluxes and clouds in the polar regions. Availability of the new satellite data from the NASA EOS program provides an opportunity to investigate the strength of the sea ice and cloud cover influence on the TOA albedo.
Project description: We intend to analyze the outputs of coupled GCMs in order to evaluate model simulations of sea ice and cloud effects on the reflected solar radiation. The model results will then be compared to the observations which will include monthly TOA radiative fluxes (CERES/ERBE); sea ice concentrations (HadISST1 and MODIS); and cloud properties (MODIS, TOVS Polar Pathfinder, and available ground-based observations). The main objectives of the project are: 1) to compare seasonal variability of sea ice concentrations and polar cloud properties simulated by the models and in observations; 2) Estimate how much changes in sea ice concentration affect the TOA albedo during various cloud conditions; 2) Study the relationship between the fraction and optical depth of low-, mid-, and upper-level clouds and the TOA albedo; 3) Study the covariability of sea ice cover and cloud properties and assess how much clouds are affected by sea ice changes; 4) compare the sea ice, cloud, and TOA albedo changes in the future climate runs from different models.
Model data required: 1) TOA radiative fluxes; 2) Surface heat fluxes: latent and sensible heat fluxes; shortwave, and longwave radiative fluxes; 3) Low-, mid-, and high-level cloud properties; 4) sea ice concentration; 5) surface ice and ocean temperature; 6) winds at all levels; 7) divergence of heat and humidity at all levels. |
| Publications: |
- Gorodetskaya, I. V., B.-L. Tremblay, B. Liepert, M. A. Cane, and R. I. Cullather, 2008: The Influence of Cloud and Surface Properties on the Arctic Ocean Shortwave Radiation Budget in Coupled Models. J. Climate. In press. Abstract. Full Article. Edit.
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