presented by Vanda Grubisic, Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada
Atmospheric rotors, intense low-level horizontal vortices that form
along an axis parallel to, and downstream of, a mountain ridge in
association with large-amplitude mountain waves and windstorms, can
pose a great hazard to aviation. Despite their considerable impact on
human activity, there has been no systematic investigation of rotors in
the last 30 years in part because rotors, with their high degree of
intermittence, are difficult to sample with in situ aircraft
measurements only and are too small in spatial scale to be routinely
sampled by conventional observing networks. Rotors are also strongly
coupled to both the structure and evolution of overlying mountain waves
and the underlying boundary layer. It is only with recent advances in
remote sensing, analysis techniques and numerical modeling, that it has
become possible to investigate in detail the structure and evolution of
all elements of the rotor coupled system.
A two-phase coordinated effort has been launched recently to study
atmospheric rotors and the rotor coupled system. The Sierra Rotors
Project, which took place in spring 2004 in the southern Sierra Nevada
in California was an exploratory Phase I of this effort. The objective
of SRP was to establish quantitative characteristics of the rotor
behavior in Owens Valley as well as to evaluate the extent to which
current operational mesoscale models can reliably forecast the
occurrence of rotors in preparation for Phase II, the upcoming
Terrain-induced Rotor Experiment (T-REX) in 2006. Observations in SRP
were collected in the lee of the Sierra Nevada by a micronetwork of
surface meteorological stations, NCAR/EOL ISS (MAPR and MISS),
time-lapse video camera, and an instrumented vehicle, and on the upwind
side by the NCAR/EOL MGLASS and a special GPS rawinsonde site in the
San Joaquin Valley. Analysis of observations and high-resolution
modeling of an observed event from the Sierra Rotors Project will be
discussed in more detail.
Seminar is from
3:30 pm to 4:30 in FL2 Room 1022
on Monday, April 4, 2005.
|
