A Correction for the Errors in Ship Reports of Light Winds

Barry B. Hinton Space Science and Engineering Center, University of Wisconsin-Madison, Madison, WI 53706

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Donald P. Wylie Space Science and Engineering Center, University of Wisconsin-Madison, Madison, WI 53706

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Abstract

The errors in ship wind reports of light winds tend to significantly bias their mean. This occurs because wind speed is a scalar quantity that is constrained to zero or positive values. Therefore, observations tend to overestimate the light winds because of the one-sided distribution of errors, but the bias disappears under stronger winds. A method for removing this bias from ship data is presented. In particular, the method is applied to interpreting the ratios of wind speeds observed by ships to those obtained from tracking low level clouds. Contracted ratios allow low cloud speeds to serve as proxy data for surface based observations.

Abstract

The errors in ship wind reports of light winds tend to significantly bias their mean. This occurs because wind speed is a scalar quantity that is constrained to zero or positive values. Therefore, observations tend to overestimate the light winds because of the one-sided distribution of errors, but the bias disappears under stronger winds. A method for removing this bias from ship data is presented. In particular, the method is applied to interpreting the ratios of wind speeds observed by ships to those obtained from tracking low level clouds. Contracted ratios allow low cloud speeds to serve as proxy data for surface based observations.

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