Climatological aspects of convective parameters from the NCAR/NCEP reanalysis

Proximity sounding analysis has been a powerful tool for developing relationships between observed environmental conditions and severe thunderstorm and tornado occurrence. Recently, Brooks et al. (2003) used the NCAR/NCEP reanalysis to develop pseudo-soundings for use in proximity studies. The reanalysis has data every six hours at a spacing slightly better than 2°x2°, with 27 sigma levels in the vertical. Using 3 years worth of data from one time per day at one-fourth of the land points in the reanalysis data set, Brooks et al. made an estimate of the global distribution of significant severe thunderstorm and tornado environments. Here, we consider 42 years of soundings at all 4 times per day over regions covering most of the contiguous United States, Europe, and Australia (approximately 82 million soundings). Annual cycles of convectively important parameters, such as convective available potential energy, shear, lapse rates, boundary-layer absolute humidity, and the lifted condensation level have been evaluated at selected points, as well as combinations of some of the parameters. Average values and variability have been considered. Finally, an updated version of the Brooks et al. thunderstorm estimates will be provided for the regions.

Reference:

Brooks, H. E., J. W. Lee, and J. P. Craven, 2003: The spatial distribution of severe thunderstorm and tornado environments from global reanalysis data. Atmos. Res., 67-68, 73-94.