FLAT90 Project
Introduction
The First Look At Turbulent kinetic energy (FLAT) experiment,
with investigators Steve Oncley (NCAR/ATD), Jim Wilczak (NOAA/WPL),
Tom Horst (NCAR/ATD), John Wyngaard (NCAR/MMM), and Al Bedard (NOAA/WPL),
was the first attempt to measure directly all terms of the
turbulent kinetic energy (TKE) balance in the atmospheric
surface layer. TKE is a basic quantity in turbulence research,
yet its balance is not known to better than 10\% due to the lack
of complete data set. Current controversy in micrometeorology
centers around this 10\% difference between several, supposedly
high-quality, existing data sets.
The FLAT experiment was carried out from September through November,
1990. This time of year was chosen to maximize the chances for
near-neutral stability conditions (overcast, strong winds) to occur,
yet to obtain data in convective conditions early in the experiment.
ATD supported FLAT with the ASTER, PAM, and Mobile CLASS systems.
The ASTER facility was used as the basis of the FLAT experiment, by supporting
a wide variety of turbulence sensors, including several "piggy-back"
investigators. A 3x3 array of NCAR PAM stations centered
on the ASTER site and spaced every 2 miles was used to check the horizontal
homogeneity of the flow field. Also, the NCAR Mobile Class system made 60
soundings during late October in an attempt to measure horizontal temperature
advection in the boundary layer.
In addition, several other organizations supplied facilities for this study:
- During the entire experiment, a NOAA/WPL 915~MHz wind profiler and an
acoustic sounder was operated at the ASTER site.
- NOAA/ATDD deployed about 9 microbarographs to examine gravity waves
and made several balloon soundings.
- Colorado State University also made
balloon soundings on two (or three) days from the ASTER site.
Steven Oncley<oncley@ucar.edu>
Last modified: Tue Apr 28 13:31:41 1998