Validation of Measurements of Water Vapour From the Halogen Occultation
Experiment, HALOE
J. E. Harries (1), J. M. Russell III (2), A. F. Tuck (3), L. L. Gordley
(4), P. Purcell (2), K. Stone (4), R. M. Bevilacqua (5), M. Gunson (6),
G. Nedoluha (5), and W. A. Traub (7)
(1) Blackett Laboratory, Imperial College of Science, Technology,
and Medicine, University of London
Phone: 71-594-7670
Fax: 71-594-7681
E-Mail: harries@haloe.larc.nasa.gov
(2) NASA Langley Research Center, Hampton, VA 23681
(3) NOAA Aeronomy Laboratory, Boulder, CO 80304
(4) G & A Technical Software, Hampton, VA 23666
(5) Naval Research Laboratory, Washington, DC 20375
(6) Jet Propulsion Laboratory, Pasadena, CA 91109
(7) Harvard Smithsonian Astrophysical Laboratory, Cambridge, MA 02138
ABSTRACT
The HALOE experiment is a solar occultation limb-sounder which operates
between 2.45 and 10.0 µm to measure the composition of the mesosphere,
stratosphere, and upper troposphere. It flies on board the Upper Atmosphere
Research Satellite (UARS), which was launched in September 1991. Measurements
are made of the transmittance of the atmosphere in a number of spectral
channels as the sun rises or sets behind the limb of the atmosphere. One
of the channels, at 6.60 µm, is a broad-band filter channel tuned
to detect absorption in the Ã2 band of water vapour. This paper
describes efforts to validate the absolute and relative uncertainties (accuracy
and precision) of the measurements from this channel. The HALOE data have
been compared with independent measurements, using a variety of observational
techniques, from balloons, from the ground, and from other space missions,
and with the results of a 2-D model. The results show that HALOE is providing
global measurements throughout the stratosphere and mesosphere with an
accuracy within ± 10% over most of this height range, and to within
± 30% at the boundaries, and to a precision in the lower stratosphere
of a few percent. The H2O data are combined with HALOE measurements of
CH4 in order to test the data in terms of conservation of total hydrogen,
with most encouraging results. The observed systematic behavior and internal
consistency of the HALOE data, coupled with these estimates of their accuracy,
indicate that the data may be used for quantitative tests of our understanding
of the physical and chemical processes which control the concentration
of H2O in the middle atmosphere.
J. Geophys. Res. (1996), Vol. 101, 10205-10216
Back to
HALOE homepage.
Back to SPAT home
page.
Last modified 25/01/1999.
WWW page comments to Graeme Willoughby