Eskimo Will wrote:


"Norman" wrote in message
...
Eskimo Will wrote:


"Norman" wrote in message
...
Metman2012 wrote:

snip

No doubt there have been changes which may have been significant, but
then don't the climatologists make allowances for this. I know that
even such mundane things as SST measurement had to be adjusted by the
method and material of actually measuring the sea temp - the
buckets used to get the water had different characteristics and
work was done to homogenize the results.

Just my 2 pennyworth


As you imply, the sea surface temperature measurement can vary
significantly dependent on what method is used for the measurement.
Unfortunately, the method used is not usually recorded. For example,
on the Ocean Weather Ships (at least on the British ones) any one of the
following could be used:

- canvas bucket (usually used only in relatively benign
weather) - rubber bucket (usually used only when under way)
- thermistor loctated somewhere in the engine-room sea water
intake - direct measurement of the engine-room sea water
intake (turn on a tap and stick a thermometer into the water)

The first 2 methods sampled the water at, or very close to the surface.
The other 2 sampled the water a few metres below the surface. It was up
to the individual observer to decide which method was used at each
observation. I don't know if any comparative tests were ever made. I
can't recall any during my time on the Weather Ships.


So the years of research put into homogenizing the SST dataset was a
waste of time as vital information would be missing?


I don't know how the homogenisation could be done if the method used for
each SST temperature measurement was not known.


That is my point. If they, (David Parker et al), have made assumptions about
how various ships made measurements over the years then the integrity of the
extremely important global homogenized SST dataset used to make judgements on
how temperature has changed over the decades may be in doubt. This needs to
be followed up as the implications could be massive.

Will

I can only speak for the methods used on one Weather Ship over a 4-year period
in the 1960s. It was 'recommended' that, whenever possible, the canvas bucket
method was used at the main synoptic hours (00/06/12/18z) but other than that
it was pretty much at the whim of the individual observer. In practice, the
canvas bucket was sometimes used in benign weather in daylight. It was seldom
used in heavy weather and probably almost never during the hours of darkness.
It was probably used more often at 12z than at any other hour. Some observers
used the canvas bucket much more often than others.

Measuring the sea water intake temperature directly with a thermometer was
probably an accurate measurement but it wasn't the sea surface temperature. It
was the temperature from a few metres below the surface. It was a method that
was used only occasionally as it meant climbing down two flights of ladders
into the bowels of the engine room. The most frequently used method was the
so-called 'thermistor'. The sensor was somewhere in the engine room sea water
intake with the read-out in the Met Office. Rumour had it that its accuracy was
rather less than desirable but I don't know if that was true. The fact is that
it was the most user-friendly method of getting the sea temperature on a filthy
wet and stormy night.

When the ship was under way the canvas bucket wasn't used. The alternative (if
either of the seawater intake methgods weren't used) was to use a slim rubber
bucket designed to be used over the stern of a moving vessel. Even while on
station the ship was often under way to get back onto or upwind of the nominal
position.

Unless my memory fails me, the Meteorological Logbook had no provision for
indicating the method that was used.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org