The Mesa Lab becomes a test bed for GPS observations
Left to right: Sandy MacDonald (director of NOAA Forecast
Systems Laboratory), GST director Randolph "Stick" Ware, and
NCAR director Tim Killeen unveil the new GPS receiver.
(Photo by Carlye Calvin.)
The receiver is now atop the Mesa Lab's B1 tower. (Photo by
Carlye Calvin.)
The striking view toward the east that wows visitors to the Mesa
Lab is now serving a scientific purpose. UNAVCO, part of UOP's GPS
Science and Technology Program (GST), installed a Global
Positioning System receiver this summer on a tripod atop the lab's
B1 tower. The receiver measures slant-path signals, those arriving
at low angles and thus passing through the lower atmosphere for
long distances. Recently Sandy MacDonald, director of NOAA Forecast
Systems Laboratory, demonstrated that the combination of slant GPS
with wind radar and microwave profiler data can provide high-
resolution three-dimensional moisture and wind fields. Such a
three-dimensional picture may improve local-area models. According
to GST director Randolph "Stick" Ware, "The moisture field has been
very poorly sampled [to date], and yet it is fundamental to climate
and weather. Slant GPS measurements can improve the definition of
atmospheric moisture fields." In a forthcoming paper in the
Journal of Geophysical Research, Aiguo Dai (CGD) and
coauthors show that GPS measurements capture the diurnal ebb and
flow of precipitable water, something that twice-daily radiosondes
can't do. Francois Vandenberghe (RAP) is comparing the technique's
results to model output. The ML tower site is part of SuomiNet, an
NSF-sponsored UOP program that is establishing real-time GPS
stations for atmospheric sensing at universities in the United
States and abroad.
