Impacts of terminal velocity on the trajectory of winter precipitation types

Thériault, J. M., R. E. Stewart, and W. Henson (2012), Impacts of terminal velocity on the trajectory of winter precipitation types, Atmos. Res., 116, 116-129, doi:10.1016/j.atmosres.2012.03.008.
Abstract: 

It is common to observe many types of precipitation such as wet snow, ice pellets, and freezing rain during winter storms. The vertical temperature profile composed of a melting layer aloft and a refreezing layer below, plays an important role in the formation of these precipitation types. The horizontal wind also influences the particle trajectories and displaces them into different atmospheric conditions as they fall. This study investigates the sensitivity of the precipitation type distribution and intensity at the surface to the precipitation terminal velocity variation down through the atmosphere. To address this issue, the trajectories of precipitation types are investigated using a bulk microphysics scheme coupled with a two-dimensional kinematic cloud model. The model is initialized with idealized atmospheric conditions associated with a warm front leading to many types of precipitation at the surface. A systematic study was carried out assuming two melting snow scenarios: snow melting aloft into rain and snow melting aloft into semi-melted snow and rain. First, the results show good agreement with observations collected during the Canadian CloudSat/Callipso Validation Project (C3VP) field campaign. Second, the sensitivity experiments show that the intensity and location of precipitation vary depending on the melting scheme. The precipitation rate at the surface can be up to 55% higher if snow melts into semi-melted snow and rain compared to directly into rain. Overall, the terminal velocity of the precipitation types observed during winter storms is critical for better predicting the location and intensity of precipitation.

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Mission: 
CloudSat