Diabatic effects on late-winter cold front evolution: Conceptual and numerical model evaluations

The impact of diabatic heating on late winter frontogenesis is evaluated bo th through conceptual scaling and the use of high-resolution Era Model simu lations of a strong but relatively dry cold surface front that occurred dur ing the Storm-scale Operational Research Meteorology Fronts Experiment Syst ems Test (STORMFEST) project. Although skies were clear ahead of the front, it was trailed by an extensive area of cloud cover that influenced frontal strength during the daylight hours by reducing solar insolation and sensib le heat flux. An Era control simulation of the event agreed reasonably well with observat ions and indicated intensification of the frontal temperature gradient duri ng the daytime with a weakening at night. Additional simulations have been done to investigate sensitivity to several diabatic processes. These tests include the role of cloud shading on surface sensible heat flux, the role o f soil moisture in the warm sector, and the role of evaporative cooling of precipitation in the light precipitation area behind the cold front. All of these diabetic processes have a measurable impact on the front. although s oil moisture and cloud shading appear to play the most important roles. The moisture and static stability of the frontal environment were unfavorable for precipitation along the front, and the increase in frontal strength due to reduced surface sensible heat flux from extensive cloud shading behind the front did not significantly influence near-front precipitation for this event.