You guys didn’t trust the engineer on watch to tell you the sea temperature?
Who knows what they’re up to down there?
Technically the preferred method of measuring SST (sea surface temperature) is by bucket as opposed to by sea suction because the bucket gets the actual surface temp as opposed to several meters below the surface. On the wx obs forms there is a box to check as to which method is used.
With a flat sea, the fall of water temperature with depth can be continuous. The real surface temperature may be used to determine the possibility of mist and fog, or other things.
For a depression growing into a hurricane, or not, the mean water temperature of the whole uppermost layer of up to 200 meters is crucial.
According to wikipedia the sea water intake also has a bias.
The first automated technique for determining SST was accomplished by measuring the temperature of water in the intake port of large ships, which was underway by 1963. These observations have a warm bias of around 0.6 °C (1 °F) due to the heat of the engine room
A warm bias due to the heat of the engine room is surprising given the flow rates involved and location of the thermometer sensor (at or near the sea chest).
A whole 1 degree. Doesn’t just moving around heat it up?
No. Thermal mass especially in moving water takes care of that.
The source cited in Wikipedia doesn’t support the 0.6 C, that I could see. I’d expect that there is a lot of literature on the subject of weather observation errors but just a quick look the bias 0.3 C seems to be a good estimate.
The range appears to be 0.2C to 0.8) one big variable is the location of the sensor in the E/R.