Thursday, 2 August 2001: 4:29 PM
Some dyanmical aspects of the Mistral (formerly paper P6.16)
During the SOP period (9/15-11/15, 1999) of the Mesoscale
Alpine Program (MAP), two Mistral events were observed.
The first event occurred
on 1 October, when a shallow Mistral flow developed in
the passage of a short-wave trough in the Alpine region. Two research
aircrafts flew a vertical box pattern across the Mistral near
the French coast and over Mediterranean Sea.
The strong Mistral flow,
a well defined shear zone, and reversed flow in the lee of western Alps were
The second event occurred
on 6 November, when a deep Mistral flow developed
as an intense north Atlantic short wave trough
moved into the western Alps region, and a Mediterranean cut-off
low moved slowly toward the southeast. This time
four aircrafts flew stacked in the vertical
across the same section as on October 1st.
This second event had a narrow shear zone and persistent
strong Mistral wind as well.
During both events, intensive radio-sounding and rapid-scanning
of MeteoSat were conducted.
In this study, the flow structure in the Mistral and their dynamical
aspects were examined based on the analysis of data (i.e.
flight level data,
drop-sounds, satellite images, SABL images, and radio-sounding),
numerical modeling, and scale analysis.
Two issues are addressed in this case study: a)
the mechanism of Mistral formation
such as the effect of low level inversion and/or
dip of tropopause, streamline splitting, flow turning, flow acceleration,
and geostrophic adjustment processes; b) the structure of Mistral
such as the vertical momentum distribution, shear zone formation,
and potential vorticity generation.