Showing papers by "Gerald L. Potter published in 1986"

Climatic effects of anthropogenic arctic aerosols: An illustration of climate feedback mechanisms with one- and two-dimensional climate models

Abstract: Two climate models, a one-dimensional radiative-convective model and a seasonal statistical-dynamical model, have been used to obtain a qualitative understanding of climate forcing mechanisms and feedback processes associated with the climatic impact of carbonaceous Arctic aerosols. The models are consistent in suggesting that such aerosols should produce surface warming in Arctic regions, but the manner in which this is accomplished is a bit unusual. Since the aerosols appear in a region and season for which the atmosphere exhibits strong static stability, aerosol-induced changes in the surface radiation budget would be expected to govern the change in surface climate. Although the direct impact of the aerosol is to reduce absorbed solar radiation at the surface, this effect is minimized by the high surface albedos, which in turn, due to the large surface reflection, enhance aerosol solar absorption. This aerosol-induced atmospheric heating then results in increased infrared emission from the atmosphere to the surface that more than compensates for the reduced surface solar absorption, thus producing surface warming. The seasonal statistical-dynamical model further exhibits interesting cryospheric feedback processes, while suggesting springtime Arctic warming that is roughly consistent in timing with observed trends in high latitude temperatures, an effect some have attributed to CO2-induced changes.

Narrow- and broad-band satellite measurements of shortwave radiation - Conversion simulations with a general circulation model

Abstract: The Oregon State University/Lawrence Livermore National Laboratory general circulation model has been employed as a vehicle for suggesting and exploring various means of converting narrow-band measurements of reflected solar radiation from the earth-atmosphere system to broad-band quantities. For purely illustrative purposes within the model's solar radiation routine, a narrow-band filter function consisting of a square-wave window extending from 0.5 to 0.9 microns is adopted. A limitation of the model, for this sort of endeavor, is that it does not include the wavelength dependence of surface albedos. Nevertheless, the model simulations tend to mimic the calibration of a narrow-band instrument, utilizing reflected solar radiation from the earth-atmosphere system as simultaneously measured by a collocated broad-band instrument; for the model, however, this is done in terms of fluxes, in contrast to instrument-measured radiances. The model results suggest that it might be preferable to perform narrow- to broad-band conversions in terms of planetary albedo (or an equivalent quantity), rather than in terms of reflected fluxes or radiances. Further improvement is achieved if, for instruments that can differentiate between clear and overcast conditions, separate clear and overcast calibrations are performed.