A cloud model sensitivity study of the environmental temperature profile on the thunderstorm development

It is well known that atmospheric temperature and humidity conditions affect the thunderstorm development as they are the main deciding factors influencing the storm thermodynamics. However, the detailed processes in which the storm development may respond to changing environmental temperature and humidity conditions are not well understood. It is often difficult to compare one storm from another from observational data simply because of the very complicated actual environmental conditions associated with each storm. On the other hand, a well-formulated storm model is very convenient for this purpose because one can vary key parameters while keeping others unchanged.

In this study, we use the three-dimensional non-hydrostatic Wisconsin Dynamical/Microphysical Model (WISCDYMM) to carry out a sensitivity study to understand the response of a storm system to different environmental temperature profiles. We use the 2 August 1981 CCOPE supercell storm as the base case for this study. A control run using the original CCOPE sounding is executed first. Then we modify the temperature profile by adding +2°C (warm case) and -2°C (cold case) to the temperatures at each level. These modified profiles resemble those that may occur in the global warming and cooling scenarios. In all experiments, the relative humidity and vertical wind shear are kept constant.

The results indicate the warm storm has higher cloud top, wider cloud anvil and stronger vertical motions, but the initial cloud layer was thinner than the normal and cold cases. On the other hand, the cold storm not only has thicker initial cloud layer and more cloud top plum present, but also stronger vertical motions than the control case in the first 80 min. More details of the results will be presented in the conference.