William G. Read talks with
ScienceWatch.com and answers a few questions about
this month's Fast Breaking Paper in the field of
Geosciences.
Article Title: Aura Microwave Limb Sounder upper
tropospheric and lower stratospheric H2O and relative
humidity with respect to ice validation
Authors: Read, WG, et al.
Journal: J GEOPHYS RES-ATMOS
Volume: 112
Issue: D24
Page: art.
Year: no.-D24S35 DEC 28 2007
* CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA.
* CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA.
(addresses have been truncated)
Why do you think your paper is highly
cited?
The paper describes an assessment of the accuracy and precision of a rather
unique water vapor data measured by satellite in the atmosphere from 8km to
20km. At these altitudes, the atmosphere is very dry and cold. Water vapor
concentrations are 100 to 1,000 times smaller than that near the surface,
yet water vapors at these heights strongly affect the climate and
stratospheric ozone layer stability.
Operational satellites that make regular water vapor measurements for
weather forecasting purposes are not sensitive enough to make these
measurements, while the few satellite instruments that have the sensitivity
rely on solar occultation, but can only make 30 measurements per day
because they use sunrises and sunsets which occur twice per satellite
orbit.
"The biggest challenge with the new
instrument is that of reducing the vertical
sampling of the humidity
measurement."
The Microwave Limb Sounder on the Aura satellite, using a long path Earth
limb-viewing geometry, observes passive thermal emission from the water
molecules, with the sensitivity to measure the low concentrations. The MLS
measures nearly 3,500 water vapor profiles every day. The data are being
used in several scientific publications to answer questions regarding the
Earth's climate, dynamics, and chemistry. The strength of any scientific
conclusions must rest on the quality of the data used and this paper
addresses this fundamental need.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Not specifically in this paper, papers describing the instrumentation and
data processing are cited by this paper.
Would you summarize the significance of your paper in
layman's terms?
It helps to provide confidence in future projections derived from climate
models.
How did you become involved in this research, and were
there any problems along the way?
I joined the MLS team in 1985, originally trained as a spectroscopist.
Spectroscopy is a fundamental part of the instrument signal analysis and I
became involved in atmospheric signal modeling. On our first-generation
instrument, which was launched in 1991, I developed a method for measuring
water vapor in the upper troposphere down to 8 km. The importance of water
vapor at these heights was great enough that our follow-up instrument, the
subject of this paper, was specifically designed to make this measurement.
The biggest challenge with the new instrument is that of reducing the
vertical sampling of the humidity measurement. With the previous
instrument, and in the first data release from this instrument, the
vertical measurements were separated every 2.7 km. The current data version
has cut this in half, to 1.3 km.
Where do you see your research leading in the
future?
I would like to see our data become routinely used in real time by
numerical weather forecasting models, in order to improve weather forecasts
and future climate projections.
Do you foresee any social or political implications for
your research?
Hopefully, more accurate weather and climate forecasting will be the
result.
William G. Read
Principal Research Scientist
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA, USA Web
Keywords: microwave limb sounder, aura satellite, water vapor
concentrations, climate, stratospheric ozone layer stability,
operational satellites, water vapor measurements, weather forecasting
purposes, solar occultation, long path earth limb-viewing geometry,
passive thermal emission, water molecules, water vapor profiles, earth's
climate, dynamics and chemistry.