RADIOSONDE
OBSERVATIONS
The investigative
team has requested the deployment of the National Center for Atmospheric
Research (NCAR) mobile GPS/Loran Atmospheric Sounding System (GLASS)
in Southwest Australia during the two intensive field campaigns. There are two proposed field campaigns: one
during the growing season in August-September and the other after the
harvest in December. High temporal resolution (4 launches/ day)
radiosonde launches will be used to examine the boundary layer evolution
and vertical wind profiles over selected study areas. Two GLASS
systems have been requested to be deployed over the selected study
areas. These study areas are selected to sample distinctly different
types and scales of spatial heterogeneities. For an extended
period the pair of GLASS systems will be deployed on the two sides
of the bunny fence, coincident with the already existing surface energy
flux measurement sites that are acquiring Bowen Ratio and other measurements.
The observations from this pair will be used to sample conditions simultaneously
on the two sides of the fence and to examine the mesoscale circulations
generated by large scale heterogeneity in the vicinity of the bunny
fence.
Another set of GLASS system deployments will take place in the adjacent
native vegetation/ agricultural areas close to the coast for part of
the field campaign. These measurements will be used to examine the
effect of land use on sea breeze circulations. Finally, the GLASS systems will be moved to the isolated
natural vegetation preserve in the middle of the agricultural area and to a complementary
site. Observations from this set of measurements will be used to study
the “island effect” associated with a relatively small stand of native
vegetation in the midst of a vast areas of agriculture.
The
radiosonde observations will be used for multiple applications. In
conjunction with surface energy flux measurements and satellite
observations of cloudiness, the radiosonde observations will
be used to examine the influence of land use on cloudiness. Specifically,
the interplay of surface energy flux patterns and atmospheric
stability on suppression or enhancement of cloudiness will be
explored using statistical techniques. The
radiosonde observations will be directly used for detecting the
existence of mesoscale circulations. We will utilize a
technique similar to that of Souza et al. (2000) for this purpose. From
a time series of radiosonde observations it is possible to identify
mesoscale circulations as perturbations over a large scale flow. The
orthogonal components of the wind u,v can be decomposed into
mean (U,V) and perturbation (u’, v’) parts by
using averaging. Vertical profiles of u’ and v’ can
be used to examine the existence of mesoscale circulations. Finally,
the radiosonde observations will be utilized for initializing the
RAMS numerical model, and along with satellite data they will be
used for identifying case study days.
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