HIGH-RESOLUTION NUMERICAL SIMULATION

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HIGH-RESOLUTION NUMERICAL SIMULATION OF A
DOWNBURST WIND EVENT
Objective
Background
To investigate the 3-D subcloud structure and
evolution, at high spatial and temporal
resolution, by numerically modelling the
downdraft thermodynamics and microphysics.
Numerical simulations can provide insight into
aspects of downbursts that are difficult to
observe in the field or physically simulate in
the laboratory.
Evolution of the potential temperature contours
for an isolated downburst that is translating
eastward with a velocity of Ut. 8 m/s.
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Research Carried Out
The Orf cooling source approach 1 is employed
with a dry version of the CM1 Model 2.
Prognostic equations for wind velocity, pressure,
and potential temperature are solved.
Dependency of profile shape on radial location.
Key Findings
The maximum horizontal gust occurs at 7.5 m AGL.
Vertical profiles exhibit a distinct maximum
value, except at the dominant vortex leading
edge. 1 Orf, LG, Anderson, JR, and Straka, JM
(1999). J Atmos Sci 532490-2511. 2
Bryan, GH and Fritsch, JM (2002). Mon Wea
Rev 1302917-2928.
Evolution of the horizontal velocity (U) field.