Kinematic and Dynamic Studies of Microbursts in the Subcloud Layer Derived from Jaws Dual-Doppler Radar for a Colorado Thunderstorm

摘要

The kinematic, dynamic and thermodynamic features of a simple and a complex microburst event were calculated, and comparisons were made in order to find common and unique structural features that might lead to greater insight into the physical mechanisms responsible for microburst development. Dual-Doppler radar data were judiciously edited, gridded and kinematically integrated upward from the surface, to produce a three-dimensional wind field. The perturbation temperature and thermodynamic variables were used to compute the momentum budgets and field was derived from the buoyancy equation, using the derived wind and pressure fields. The results from this study reveal some basic similarities, along with some notable differences in structure. Both cases reveal a downward flux of mass, momentum, and eddying energy within the microburst; the boundary layer above 0.75 km is the source of the mass and momentum; an intermediate level near 0.75 km acts as a conduit for the downward flux; and the surface layer below 0.75 km that comprises the divergent flow enclosed in the microburst. The microburst also included a high reflectivity core at the center. The complex case contains a misocyclone above 0.75 km. The misocyclone will hereafter refer to the cyclonic circulation above the surface microburst. Theses. (JHD)