Comparison of Different Sea Surface Temperature Measurements LCDR IVO J. PRIKASKY

Overview Motivation Collection methods Instrumentation Statistical Analysis and results Conclusions

Why do we need accurate SST measurements? EM/EO prediction of refractive properties 0.5 deg C difference significant for evaporative duct height Used in Met/Oceano models Remote sensing verification Aircraft Satellite

Depths of SST Measurement Considerations Skin SST Depth of about 10 microns Measured by radiometers Bulk SST Depth > 1 mm Buoys, ship’s intake Bucket/thermometer

Collection Methods – Skin Temp Bridge mounted Radiometers OS43L IR Sensor Aimed at 45 deg LW radiation between 8-14 microns Denoted as OSST Apogee IRT-P Sensor Aimed at 45 deg Measures LW radiation Between 6.5 -14 microns Denoted as ASST

Collection Methods – Skin Temp cont. Hand-held Radiometers Heitronics KT-19 Radiometer Measurements @ 30 deg angle - Pointed @ the sky for LW sky T Stated accuracy 0.5 deg C Denoted as Heit Omega Radiometer Measurements @ 30 deg angle Measures 8-14 microns Did not work well Denoted as Omega

Collection Methods – Bulk Temperature Boom Probe – did not work Bucket Hourly measurements Calibrated using ice water, +.2 deg C error Depth of measurement varied Seachest Intake 2.5 meters deep Recorded by UDAS Away from ship’s discharge

Corrections Instrument calibration Unknown except for bucket – determined +.2 deg C For radiometers, specular reflection corr. Using formula Applied to all radiometer measurments

General Analysis Seachest 11.22 0.98 Bucket 10.32 1.11 Heit 11.02 0.95 Measurement Type Mean (deg C) Std. Deviation (deg C) Seachest 11.22 0.98 Bucket 10.32 1.11 Heit 11.02 0.95 Omega 7.79 1.80 ASST 8.56 4.49 OSST 8.78 1.61

Time Series – H/H Radiometers

T. Series – Bridge Mount. Radiometers

Time Series - Bulk Methods

Difference with Seachest Measurement Type Mean (deg C) Std. Deviation (deg C) Heit-seach. 0.4328 1.3105 Heitcor-seach. -0.2657 1.1275 Bucket-seach. -0.9556 1.4168 ASST-seach. 1.5666 1.7007 ASSTcor-seach. -0.8910 1.9267 OSST-seach. 2.2314 1.4983 OSSTcor-seach. -1.5408 1.4467

Conclusions Seachest Temp appears to be most reliable Human factor! Little correlation among different measurements Instrument calibration critical Measuring SST accurately is challenging

Questions?