Project Title:

An Optical Instrument to Measure Liquid Water Content and Droplet Spectra in Clouds

92-1-01.03-1105                                                   NAS03-26905
An Optical Instrument to Measure Liquid Water
     Content and Droplet Spectra in Clouds
Spec, Inc.
5401 Western Avenue
Boulder, CO  80301
R. Paul Lawson                                       (303-449-1105)

Abstract:

     Measuring liquid water content and drop spectra in clouds is
fundamental to most meteorologic studies such as the formation and
evolution of precipitation, the radiative effect of clouds on
climate change, atmospheric chemistry, and aircraft icing.
Presently, measurements of liquid water content in clouds are
notoriously unreliable. While some improvements have occurred over
the past two decades, instruments available for the measurement of
cloud liquid water content still perform inadequately. Phase I
will investigate an optical technique that provides a direct
measurement of liquid water content and drop spectra from an
ensemble of drops in the sample volume. A prototype instrument
will be built that measures the forward scattered light with an
angular resolution of 0.033ø. The angular measurements of light
intensity can be processed in real time to provide two outputs:
liquid water content after appropriate weighting of the basis
functions and drop spectra from inversion of the (overdetermined)
intensity matrix. These concurrent measurements can be made with a
spatial resolution of 0.1 m from an aircraft. In Phase II, an
airborne version of the instrument will be built and tested.

Potential Commercial Application:

Potential Commercial Applications:  An instrument which reliably
measures liquid water content and drop spectra in clouds will be
useful on research aircraft, and may be necessary to evaluate the
effects of clouds on climate change. The instrument might also be
used as an icing severity indicator on passenger and military
aircraft. As a ground-based device, the instrument will not
require airspeed measurements and can be used to measure the
riming rate on mountaintops, providing an estimate of acid
deposition. It can also be used to measure visibility at airports.

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