"Col" wrote in message
...
|
| wrote in message
| ...
| Can anyone explain to me how whilst it's -2.5C and vis is not that
| good here in North Yorks with a light breeze, there's no frost and no
| standing water is frozen - that includes our little garden pond or any
| of the puddles on the road side or in the fields...
|
| I dunno, everything frozen solid here. Some frost but not a great deal.
| And it's even snowing!
| --
| Col
|
| Bolton, Lancashire
| 160m asl
|

In some areas relatively warm air is drifting about not that far aloft. It
has either been advected in at that level above the sirface flow or has been
generated by subsidence in the anticyclone currently in residence. The
fairly widespread cloud layer which has appeared would be just under this
"inversion" layer and would receive some of the warmth from the air above.

Yesterday (31 Dec) here in the Deep South we had a rare "ice day", but there
was only a light frost deposit due to the cloud reducing radiation to space
and relatively dry air. The temperature was hovering between -1C and -2C
throughout. This morning the thermometer was slowly rising towards -1C.
Eventually it rose above freezing, but long before this happened all hoar
deposit had gone and the ice was starting to thaw around the edges of the
birdbath.

The most likely explanation is that downward radiation from the relatively
warm cloud layer warmed the surface above freezing while subzero air was
being advected in from areas which were still frostbound. Clear air is
fairly transparent to near infra-red radiation (else satellite sensors and
infra-red cameras wouldn't work) so the main heating / cooling effect is via
the ground with the air temperature responding later.

Happy New Year to you all, and here's hoping for a summer *not* like 2007 or
2008. Quite apart from anything else, I'd like to get a few decent cricket
seasons in while I'm still young enough to play!
--
- Yokel -
oo oo
OOO OOO
OO 0 OO
) ( I ) (
) ( /\ ) (
Yokel @ Ashurst New Forest
SU 336 107 17m a.s.l.

"Yokel" posts via a spam-trap account which is not read.