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Nowcast Products
CAL-VAL
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The Cal/Val algorithm uses the 19V and 37V channels within
the ice pack and the 37V and 37H channels near the ice edge if weather
effects are not important. A series of automated tests, using thresholds
of brightness temperature combinations is used to determine concentration.
The Cal/Val is a modified version of the AES-York algorithm and was initia
lly
developed for the calibration and validation of SSM/I. The use of only
the 37 GHz channels near the ice edge yields a higher resolution ice/water
boundary because of the smaller footprint of the 37 GHz channels compared
to the 19 GHz channels. The Cal/Val is also quite sensitive to thin ice;
any underestimation of thin ice is much less than from the NASA Team algor
ithm.
For these two reasons, the Cal/Val has historically been the primary algor
ithm
used operationally at the National Ice Center. However, because the Cal/Va
l
is particularly sensitive to thin ice, it almost always saturates quickly
to 100% (and greater) ice concentrations. Thus, small variations in high
concentration areas are not detectable. Hollinger, J.R., R. Lo, G. Poe,
R. Savage, and J. Pierce, 1991. "Special Sensor Microwave/Imager Calibrat
ion/Validation",
Washington, DC, U.S. Naval Research Laboratory (Final Report). Ramseier,
R., I.G. Rubinstein, and A.F. Davies, 1988. "Operational evaluation of
Special Sensor Microwave/Imager by the Atmospheric Environment Service",
Centre for Research in Experimental Space Science, York University, North
York, Ontario. North York, Ontario, Centre for Research in Experimental
Space Science, AES, York University (Report).
If you have any comments, please E-mail the National Ice Center Liaison
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