Abstract
Some kinematic, dynamic, and thermodynamic structures of a multiple microburst-producing storm, which occurred on 5 August 1982 in Colorado, were studied for three analysis times at 1845, 1847, and 1850 MDT. Dual Doppler data collected during the project of Joint Airport Weather Studies (JAWS) at Denver's Stapleton International Airport were objectively analyzed to produce a three- dimensional wind field. The domain of interest had a horizontal dimension of 15 km by 15 km covering three microbursts. There were five analysis levels in the vertical ranging from 0.25 to 1.25 km AOL. The horizontal and vertical grid spacings were 0.5 and 0.25 km, respectively. Vertical velocities were computed by integrating the anelastic continuity equation upward from the surface. Subsequently, fields of deviation perturbation pressure and temperature were recovered from a detailed wind field using the three momentum equations. These fields were then subjected to internal consistency checks to determine the level of confidence before interpretation. Results show that the microbursts being investigated are embedded within the high-reflectivity cores with heavy precipitation. A wet microburst is accompanied by the misocyclone at levels above 0.75 km in the downdraft. It has the slowly descending downfiow forming a cold core at the lowest levels due to the evaporation of raindrops. Near the gust front (GF), a mesocyclone-like circulation develops in the area where the warm, dry environmental air interacts with the negatively buoyant microburst outflow. High pressure forms inside the microburst core with low pressure in the strong wind regions. Pronounced horizontal pressure gradients occur from the microburst center outward to balance the strong diverging outflow that region. The retrieved pressure and temperature fields agree well with the storm's kinematic structure. The combined effects of misocyclone circulations, perturbation pressure gradients, buoyancy and precipitation loading are responsible for maintaining the microburst downdrafts in the atmospheric boundary layer (ABL).
Highlights
In the Doppler study by Wilson et al (1984), a microburst is defined as a downdraft-induced, damaging horizontal flow near the surface, whose hori zontal dimension is less than 4 km, and whose differential velocity is greater than 10 m/s
Using the dual-Doppler data collected during the Joint Airport Weather Studies (JAWS) project, Lin et al (1987) and Lin and Hughes
This mesohigh was accompanied by low pressure in the strongest outflow regions, forming a pronounced horizontal perturbation-pressure gradient outward from the high pressure center
Summary
In the Doppler study by Wilson et al (1984), a microburst is defined as a downdraft-induced, damaging horizontal flow near the surface, whose hori zontal dimension is less than 4 km, and whose differential velocity is greater than 10 m/s. Using the dual-Doppler data collected during the Joint Airport Weather Studies (JAWS) project, Lin et al (1987) and Lin and Hughes (1987) investigated the kinematic, dynamic, and thermodynamic structures of a microburst-producing thunderstorm which occurred on 14 July 1982 in Col orado. A strong downflow impinged on the surface, produc ing a stagnation mesohigh pressure area inside'the microburst This mesohigh was accompanied by low pressure in the strongest outflow regions, forming a pronounced horizontal perturbation-pressure gradient outward from the high pressure center. Fields of deviation perturbation pressure and virtual temperature were recovered from the derived winds using the three momentum equations These retrieved fields, together with the observed wind field, were employed to investigate certain important structural features and momentum and kinetic energy budgets of the storm, which produced multiple microbursts in the ABL.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
