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A new type of idealized global climate model and its application to dust-climate interactions
Karen M. Shell, SIO/Univ. of California, La Jolla, CA; and R. Somerville
Paleoclimatic evidence suggests that airborne mineral dust can be a climatically important atmospheric aerosol, but little is known quantitatively about the mechanisms of dust-climate interactions. We have developed an idealized global model with which to study processes and feedbacks within the dust-climate system. The model is a generalization of the energy balance approach to climate modeling. We solve numerically for equilibrium climate states defined by zonal average temperature as a function of latitude for both an atmosphere and a surface. We parameterize the effects of radiative, latent, and sensible heating, ocean heat transport, the Hadley circulation, and midlatitude atmospheric eddies. The model reproduces the mean variation of temperature with latitude and the global average heat budget within the uncertainty of observations.
Dust concentrations can influence the climate system by altering the radiative properties of the atmosphere. We determine the longwave and shortwave forcing due to dust based on specified dust distribution and optical properties. The dust forcing is comparable to that obtained in more complicated models, such as general circulation models. Since the atmospheric dust properties are not well known, we use our model to explore the response of the climate to a range of dust concentrations, distributions, and optical properties in order to determine the dust sensitivity and highlight important feedbacks within the system. The dust alters the model climate, resulting in a surface temperature decrease. However, the primary effect of dust is the reduction in latent and sensible heat transferred from the surface to the atmosphere. The latent heating changes may result in further feedbacks through changes in water vapor and precipitation.
.Session 6, Radiative Forcing of the Climate: Modeling (Room 609/610)
Tuesday, 13 January 2004, 3:30 PM-5:30 PM, Room 609/610
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