Recent numerical simulation work using idealized initial atmospheric profiles has provided quantitative evidence that perhaps at least nine basic, theoretically independent, environmental parameters act to regulate the intensity and morphology of deep convective storms. Some of the environmental parameters that could significantly influence severe storm development are: convective available potential energy (CAPE), lifting condensation level (LCL), level of free convection (LFC), deep layer vertical shear, low level shear, altitude of maximum parcel buoyancy, precipitable water, mean dewpoint depression in the 2-6 km layer, and convective inhibition (CIN). In this study we examine the warm season climatology of these parameters for the continental United states.

The National Climatic Data Center (NCDC) radiosonde database is used for deriving the climatology of the environmental parameters. The mean values of the parameters are calculated for stations that have continuous time series of soundings for at least ten years. The mean values of the environmental parameters are interpolated to a regular grid, and their spatial distributions are examined. The mean values of the parameters for areas with high and low frequency of occurrence of severe storms are compared. The temporal variations of these parameters are also analyzed, especially the variations between El Nino and La Nina years.