.... Whilst looking at this product he-

http://ows.public.sembach.af.mil/ind...ection=SFCAnal

I got to thinking, not for the first time, why some meteorologists use
the convention ' humidity-temperature ' and others the reverse, when
labelling air masses.

For example, on this chart, what I would call 'Tropical maritime' air
west of Iberia is labelled 'mT' (maritime Tropical), and over Britain
we have 'mod mP' (or modified maritime Polar), whereas I would label
it as mod Pm (etc.)

I'm not sure there is a 'right' or 'wrong' way of doing this [ except
to acknowledge Tor Bergeron's work - see below ], and looking back at
some books I have, it doesn't seem to matter which era you are in, or
which side of the Atlantic you are (which latter was my initial
thought).

Here is a list of the books which use the convention that I was taught
(School geography & Met O College), that is Tm, Pm, Pc etc.

.... [UK] Meteorological Glossary: Meteorological Office: 1939
.... [US] Through the Overcast: Jordanoff: 1939
.... [UK] Meteorology for Aviators: Sutcliffe/Meteorological Office:
1939
.... [US] Introduction to Meteorology: Petterssen: 1941 and 1958
editions
.... [UK] Observer's Book of Weather: Lester: 1955
.... [UK] Essentials of Meteorology: McIntosh & Thom: 1983
.... [UK] Handbook of Aviation Meteorology: Meteorological Office: 1994
edition

And here those using the reverse (e.g. cT, mP etc.)

.... [UK] Admiralty Weather Manual: Admiralty: 1938
.... [UK] Meteorological Glossary: McIntosh / Meteorological Office:
1972 edition
.... [UK] Climate of the British Isles: Chandler & Gregory: 1976
.... [UK] Meteorology for Mariners: Meteorological Office: 1978 edition

( Interesting to note that McIntosh switched his allegiance between
the 'Met Glossary' date of 1971 & the 'Essentials' date of 1983. )

I believe that Bergeron himself (who developed the basis of this
classification) considered the thermal properties first, then the
moisture characteristics - so it's interesting to speculate why over
time it has turned this way? I note that the vast majority of US
weather web sites as well as Wikipedia use the 'second' convention.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023