HR: 1340h
AN: A23B-0789    [Abstracts]
TI: What Controls Planetary Albedo and its Interannual Variability?
AU: * Qu, X
EM: xinqu@atmos.ucla.edu
AF: Department of Atmospheric and Oceanic Sciences, UCLA., PO BOX 951565, Los Angeles, CA 90095-1565 United States
AU: Hall, A
EM: alexhall@atmos.ucla.edu
AF: Department of Atmospheric and Oceanic Sciences, UCLA., PO BOX 951565, Los Angeles, CA 90095-1565 United States
AB: Climatological planetary albedo obtained from the ISCCP D-series flux dataset is broken down into contributions from the atmosphere and surface for various regions of the world. With the exception of Antarctica, the atmosphere accounts for much more of planetary albedo ($>$75%) than the surface. This is because surface albedo is generally small compared to atmospheric albedo and because the atmosphere attenuates the surface contribution.In Antarctica, the surface accounts for more of planetary albedo($\sim$70%) than the atmosphere during all seasons with sunshine. High surface albedo and a small atmospheric attenuation effect in the relatively transparent southern hemisphere polar atmosphere account for the large contribution of the surface. The observed poleward increase in planetary albedo was also examined. The atmosphere and the surface contribute about equally to this increase in the northern hemisphere. However,in the southern hemisphere, the surface contribution is three times larger than that of the atmosphere. This hemispheric asymmetry is largely due to the high Antarctic surface albedo. The ISCCP data sets were also used to determine what controls interannual planetary albedo variability. In a global sense, more than 90% of it can be linearly related to fluctuations in surface albedo, cloud cover and the logarithm of cloud optical depth. The atmosphere contributes more to planetary albedo variability over ice-free ocean and snow-free land areas. However, the surface is dominant in snow and ice-covered regions, accounting for more than 50% at nearly all times of year. The large effect of snow and ice variations on interannual planetary albedo variability suggests that if cloud fields do not change much in a future warmer climate, a retreat of snow cover, or sea ice would lead to a significant increase in net incoming solar radiation, resulting in an enhancement of high latitude climate sensitivity.
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting