HR: 1340h
AN: A23B-0805    [Abstracts]
TI: Comparing the Effects of Sea Ice and Cloud Variability on the Top-of-Atmosphere Albedo in Observations and GCMs
AU: * Gorodetskaya, I
EM: irina@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Tremblay, B
EM: tremblay@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Liepert, B
EM: liepert@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Cane, M
EM: mcane@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AB: Output from the Goddard Institute for Space Studies (GISS) atmosphere-only general circulation model is compared to satellite observations to assess how the top-of-atmosphere (TOA) albedo responds to changes in sea ice concentration and in cloud properties. The observations used for the comparison include monthly TOA radiative fluxes from the Radiation Budget Experiment, sea ice concentrations from UK Hadley Centre (HadISST1 data set); and cloud properties from the TOVS Polar Pathfinder. The model was run with transient sea surface temperature and sea ice concentration from the HadISST1 data set. We focus on the Northern Hemisphere polar regions during 1950-1998 in the model simulations and 1984-1990 in the observations (limited by the availability of radiation data). The short wave radiative effectiveness (RE) of sea ice concentrations is calculated as the difference in the mean TOA albedo over gridboxes with zero and maximum sea ice cover fraction. The RE of sea ice is 0.29 and 0.22 in the model and observations, respectively. The mean RE of sea ice in the model decreases almost exponentially from 0.33 to 0.1 as the monthly total cloud cover fraction increases from 0.1 to 1.0. In the model, the maximum and minimum total cloud fraction are observed in winter (0.75) and summer (0.55), respectively. On the other hand, observations from the TOVS polar pathfinder and from ground-based observations show maximum total cloud cover fraction in summer and minimum in spring. The analysis will be extended using model outputs from the Atmospheric and Coupled Model Intercomparison Projects.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3349 Polar meteorology
DE: 3359 Radiative processes
DE: 3360 Remote sensing
DE: 4207 Arctic and Antarctic oceanography
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting