Fast floating temperature sensor measures SST, not wet bulb temperature

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  • 1 College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR.
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Abstract

A small integrated oceanographic thermometer with a nominal response time of 1 s was affixed to a floating hose “sea snake” towed near the bow of a research vessel. The sensor measured the near-surface ocean temperature accurately and in agreement with other platforms. The effect of conduction and evaporation is modeled for a sensor impulsively alternated between water and air. Large thermal mass makes most sea snake thermometers insensitive to temperature impulses. The smaller 1-s thermometer cooled by evaporation, but the sensor never reached the wet bulb temperature. The cooling was less than 6% of the (~2.7 °C) difference between the ocean temperature and the wet bulb temperature in 99% of 2 s–1 samples. Filtering outliers, such as with a median, effectively removes the evaporative cooling effect from 1- or 10-minute average temperatures.

Corresponding author address: Simon P. de Szoeke, College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 104 CEOAS Admin Bldg, Corvallis OR 97331-5503. Email: simon.deszoeke@oregonstate.edu

Abstract

A small integrated oceanographic thermometer with a nominal response time of 1 s was affixed to a floating hose “sea snake” towed near the bow of a research vessel. The sensor measured the near-surface ocean temperature accurately and in agreement with other platforms. The effect of conduction and evaporation is modeled for a sensor impulsively alternated between water and air. Large thermal mass makes most sea snake thermometers insensitive to temperature impulses. The smaller 1-s thermometer cooled by evaporation, but the sensor never reached the wet bulb temperature. The cooling was less than 6% of the (~2.7 °C) difference between the ocean temperature and the wet bulb temperature in 99% of 2 s–1 samples. Filtering outliers, such as with a median, effectively removes the evaporative cooling effect from 1- or 10-minute average temperatures.

Corresponding author address: Simon P. de Szoeke, College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 104 CEOAS Admin Bldg, Corvallis OR 97331-5503. Email: simon.deszoeke@oregonstate.edu
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