Sounding techniques based on the Global Positioning System
spring to life in the animated displays produced by UCAR’s Constellation
Observing System for Meteorology, Ionosphere & Climate. The displays
show actual soundings taken at various points around the globe only
hours earlier.
When COSMIC reworked its Web site earlier this year, “we needed
a good teaser on the front page,” says COSMIC’s Douglas
Hunt. “As kind of a lark, really, I’d been trying to come
up with ways of displaying and animating Earth with one of the Perl-based
Web tools I’ve been developing.”
COSMIC’s own system won’t be launched until late 2005, so
in the meantime its Web site features on-the-fly plots of recent data
pulled from another space-based system, the Challenging Minisatellite
Payload for Geophysical Research and Application. CHAMP was launched
in 2000 by Germany’s GeoForschungZentrum Potsdam.
Every few minutes, CHAMP infers the state of the atmosphere along the
path of a GPS signal that skims just above Earth’s surface before
being intercepted by CHAMP’s satellite. The data are downloaded
every few hours to Germany, and COSMIC gets them a few hours later.
Hunt’s Perl script animates the path of the signal between the
CHAMP and GPS satellites, with an adjacent plot that animates the change
of temperature with height along the way (see sample graphic).


The site features the five most recent occultations, which are anywhere
from2 to 24 hours old. Once COSMIC is up and running, a similar program
should be able to plot soundings even closer to real time. “We’re
trying to get it all to fit within a three-hour window,” says
Hunt.