Cumulus Support

What are air frosts and how are they calculated? I have had many white frosts this winter, but data in "this month" only shows two.

Air frosts ocur when the temperature of the air (which is what your station measures) falls below freezing. The 'white frosts' you refer to are known as 'ground frosts' and occur when the temperature of the ground (which your station does not measure) falls below freezing.

More explanation here: http://weatherfaqs.org.uk/node/26

Over the last few days we here in Devon have been suffering from very low ground temperatures with air temperatures above freezing and a few light rain showers. The result has been wet ice on roads and pavements presenting a severe hazard. I think a ground thermometer would be useful - it a pity these weather stations don't have such a thing.

Just an observation - Cumulus does a great job with the data it has to work on

As a rough guide, if your thermometer is at 'standard' 1.4 => 1.7m high, then a night temp at 2.8oC or dropping is equal to 0oC ground level.

Thanks for the info