Momentum flux in the subcloud layer of a microburst-producing thunderstorm determined from JAWS Dual-Doppler data |
| |
Authors: | Yeong-Jer Lin Patrick M Condray |
| |
Institution: | (1) Department of Earth and Atmospheric Sciences, Saint Louis University, 63103 Sain Louis, Missouri, MO, USA |
| |
Abstract: | Dual-Doppler winds at 1647 MDT for the 14 July, 1982 convective storm collected during the Joint Airport Weather Studies (JAWS)
project at Denver's Stapleton International Airport were objectively analyzed to produce a three-dimensional wind field. The
domain of interest had dimensions of 10 × 10 × 8.5 km centered on the microburst. Vertical velocities were computed by integrating
the anelastic continuity equation downward from the storm's top. A variational approach was then employed to adjust the derived
three-dimensional wind field. Subsequently, fields of deviation perturbation pressure and virtual temperature were retrieved
from a detailed wind field using the three momentum equations. These retrieved fields were subjected to internal consistency
checks to determine the level of confidence before interpetation. The fields were then used to calculate the generation of
the vertical transport of horizontal momentum in the subcloud layer of a microburst-producing storm during the quasi-steady
mature stage.
Results show that the microburst occurrence in the atmospheric boundary layer (ABL) enhances eddy transfer of momentum. Direct
calculation of the vertical transport of u- and v-momentum reveals that momentum was being transferred downward from the mid-levels of the storm to the microburst. The dominant
processes contributing to the generation/dissipation of horizontal momentum flux were the total buoyancy production, pressure
effects, vertical mean wind shear and vertical transport of momentum. The above processes play an important role in maintaining
the strength of the microburst outflow in the ABL during the quasi-steady mature stage of the microburst life cycle. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|