Mesoscale Severe Weather Development under Orographic Influences

• Main Authors: Reiter, Elmar R, Sheaffer, John D, Klitch, Marjorie A
• Format: Report
• Language: English
• Subjects: ADVERSE CONDITIONS; ATMOSPHERIC MOTION; ATMOSPHERIC TEMPERATURE; BUDGETS; CHINA; COEFFICIENTS; COLORADO; COMPUTATIONS; CYCLOGENESIS; CYCLONES; DESERTS; DRAG; ENERGY; ESTIMATES; FLUX(RATE); GRIDS; HEAT FLUX; HIGH RATE; IMPLANTATION; INFRARED RADIATION; INTENSITY; KANSAS; LATENT HEAT; LOW LEVEL; Meteorology; MOUNTAINS; NEUTRAL; PE61102F; RATIOS; REMOTE DETECTORS; SCALING FACTOR; SEVERE WEATHER; STABILITY; SURFACE ENERGY; SURFACES; TRANSFER; TUNDRA; TURBULENCE; UNITED STATES; VORTICES; WEATHER; WUAFOSR2310A1

Measurements of surface energy budgets have been carried out at several sites in the Colorado Rocky Mountains, in the Kansas Prairie, in the Gobi Desert and in Tibet. The fluxes of sensible heat, H sub S, from the surface could be estimated as functions of the difference between air temperature and infrared 'skin surface' temperature, as seen by remote sensing instruments. Computations of Hs involve a neutral stability coefficient for turbulent transfer (drag coefficient), C sub T, ranging between 0.0021 (Gobi Desert) and 0.0070 (alpine tundra), and a scaling factor for stability. Latent heat fluxes were estimated either as residual of total energy fluxes or through a Bowen ratio approach. These flux estimates worked well in a mesoscale, nested-grid model over the Rocky Mountains. The model was able to predict with considerable skill flash-flood events such as the Big Thompson flood of 1976 and the Cheyenne flood of 1985. By implanting 'features' such as a vorticity maximum associated with a low-level jet stream, the model without nested grid was able to predict severe cyclogenesis ('bomb' formation) over the eastern United States. Both model versions run on a desktop workstation.