Thinking back to the last snow event in Shetland - and the (possible)
forthcoming one next week - a point to bear in mind, is that in
periods of drift snow when the fine blowing snow gets inside the
screen the result is often that the dry bulb thermometer will also
became an ice-bulb. In my experienvce this can reduce the 'air'
temperature by as much as 1.5°C - ie both 'dry'bulb and ice bulb
reading more or less the same.
Wiping the bulb with a dry cloth solves this – but you only have a
short moment before it again reverts to an ice bulb again! I hate to
think what this does to readings from AWS!

Dave
Fair Isle

Dave I noticed this effect last Sunday when here in Leeds we had fine
drifting snow. This was obviously penetrating the radiation shield on my
Davis Vanatge pro. I thought there was something wrong with the sensor as
it was reading around 1 Deg C lower than other electronic sensors I have -
On most occasions they agree withing a few decimal points, but not last
Sunday. The temperarure stabilised once the precipitation stopped and
everything dried out!
Regards
Rob
from Farsley near Leeds 366 ft AMsl
http://homepage.ntlworld.com/robert.brookes3/wx.htm



"Dave Wheeler" wrote in message
t...
Thinking back to the last snow event in Shetland - and the (possible)
forthcoming one next week - a point to bear in mind, is that in
periods of drift snow when the fine blowing snow gets inside the
screen the result is often that the dry bulb thermometer will also
became an ice-bulb. In my experienvce this can reduce the 'air'
temperature by as much as 1.5°C - ie both 'dry'bulb and ice bulb
reading more or less the same.
Wiping the bulb with a dry cloth solves this - but you only have a
short moment before it again reverts to an ice bulb again! I hate to
think what this does to readings from AWS!

Dave
Fair Isle