Numerical simulation of cirrus clouds: fire case study and sensitivity analysis
Date
1991-08-12
Authors
Heckman, Scot T., author
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Abstract
The October 28, 1986 FIRE (First ISCCP Regional Experiment) case was simulated using the Regional Atmospheric Modeling System - RAMS developed at Colorado State University. This three dimensional, mesoscale model was applied in non-hydrostatic and nested-grid mode using explicit, bulk microphysics and radiation. The simulation resulted in very good agreement between observed and model predicted dynamic and cloud fields. We verified cloud height, thickness, areal extent and microphysical composition against GOES satellite imagery, lidar, and aircraft measurements taken during the FIRE Cirrus IFO (Intensive Field Observation). We examined the simulated cirrus lifecycle to determine possible formation, maintenance and dissipation mechanisms. Sensitivity simulations were run to determine long and short wave radiative forcing. Also, a simulation was run with no condensate to examine cloud feedbacks on the environment. Cloud top generation zones, fallstreaks, and layering were simulated. Longwave radiation appeared to be instrumental in developing weak convective activity in the lower layer thereby increasing it's optical depth. Cloud top cooling and cloud base heating affected the flow around the cloud. Secondarily, we studied the effects of three upper boundary conditions on cirrus clouds in a synoptic setting.
Description
August 12, 1991.
Also issued as author's thesis (M.S.) -- Colorado State University, 1991.
Also issued as author's thesis (M.S.) -- Colorado State University, 1991.
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Subject
Clouds -- Mathematical models
Convection (Meteorology)
Mesometeorology