EVALUATION OF A NEW APPROACH TO MICROWAVE REFRACTIVITY ANALYSIS

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EVALUATION OF A NEW APPROACH TO MICROWAVE
REFRACTIVITY ANALYSIS

William T. Thompson, Stephen D. Burk, Naval
Research Laboratory, Monterey, CA Michael
Jablecki and Ted Rogers SPAWARS, San Diego, CA
.

Mesoscale numerical model analyses and forecasts
of the microwave refractivity field, M, and its
impact on EM propagation remains a significant
challenge due to several factors (i) the
relatively small vertical scale of significant M
features and (ii) subtle changes in the M-profile
can dramatically im-pact the propagation
environment (e.g., transition from elevated to
surface-based ducting). A unique data fusion
technique is used here in conjunction with NRLs
Coupled Ocean/Atmosphere Mesoscale Prediction
System (COAMPS?) to analyze refractivity. This
technique combines information from observed
soundings with model forecasts valid at the same
time (i.e., a model back-ground field). A
height-shifting and stretching algorithm is
applied to the background refractivity field in
order to bring it into close agreement with a
given sounding (or soundings). The influence of
this shifting and stretching is then broadcast
over a region of influence, S, and used to alter
the background refractivity field. Soundings
were launched every 4 h (except midnight) at 10
stations during the two-week long Variability of
Coastal Atmospheric Refractivity (VOCAR)
experiment in the South-ern California Bight.
COAMPS forecasts are produced throughout the
VOCAR period and are used to statistically
evaluate this new data fusion technique. The
shifting technique is applied throughout the
VOCAR period at a selected sounding location and
the impact of the data fusion technique on model
refractivity profiles is evaluated at three
surrounding sounding locations. The special
VOCAR soundings are of great value here in
validating this data fusion tech-nique, but once
operational the approach will not require such
high data density.
This technique could be utilized to ingest
soundings in the vicinity of a carrier strike
group in order to provide an improved
refractivity analysis for pilot briefing and
asset protection
USS GEORGE WASHINGTON Strike Group