Professor Umran S. Inan

Winter 1997-98

Date: Wednesday, February 11, 1998

Time: 4:15 PM Refreshments at 4:00

Location: Gesb 124 (Green Earth Sciences Bldg.)

The Role and Treatment of Clouds in Atmospheric Models

Dr. Mark Jacobson

Civil Engineering,

Stanford University


Clouds in the atmosphere affect the surface energy balance, the rate of gas and particle transport from the boundary layer to the free troposphere or ground, rates of photochemical reactions, and rates of change of ambient momentum, temperature, and moisture. Numerical models simulate clouds explicitly or with a cumulus parameterization. Models of both types usually treat microphysics in a simplified manner to save computer time, but some models treat microphysics in detail. Proper simulation of the effects of clouds on temperatures requires highly-resolved calculations of cloud-drop size distributions and compositions. For this talk, a general overview of the numerical treatment of clouds in regional- and global-scale models is discussed. The effects of clouds and cloud condensation nuclei on temperatures and on rates of chemical reactions in the atmosphere are also examined.