Convective energy sensitivity to temperature and moisture perturbations

Convective available potential energy (CAPE) can be used to indicate potential convection column growth over wildland fires. It depends on the vertical temperature structure of the atmosphere and on the surface air temperature and moisture content. Wildfire combustion modifies both of these surface properties, although the degree of modification is unknown. The influence on CAPE of a small increase in temperature or moisture is highly nonlinear but readily determined for a given atmospheric profile. The question of how much a fire changes the temperature and moisture of surface air is currently the subject of scientific debate, as is the question of how important these changes might be for fire behavior. This study uses the North American Regional Reanalysis (NARR) to examine ambient CAPE across North America. It then determines the sensitivity of that CAPE to small temperature increases (up to 3 °C) or mixing ratio increases (up to 3 g/kg) in surface properties. The impact of these perturbations on parcel equilibrium height (as an approximation of fire plume rise height) is also considered.