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K · 21-09-2009, 04:31 PM posted to uk.rec.gardening

Stewart Robert Hinsley writes
In message ,
writes
In article ,
K wrote:

What is a grass frost? It's a term I hadn't heard till this year, when
it's been sneaking into all the weather forecasts. And how does it
compare with a ground frost or an air frost? And how do any of these
compare with a temperature of 0 deg C (since the weather forecast is
fond of announce that there will be night time temperatures of, say, 2
deg C and therefore we can expect a frost)

I think that a grass frost and ground frost are the same thing, and
an air frost is a temperature below 0 Celsius.

An air frost is when the temperature of the air falls below 0 Celsius.
Because of cooling by radiation, and the relatively low heat capacity
and conductivity of air, at night the temperature of the surface of the
ground can fall below that of the air above it. This is a ground or
grass frost.

Thanks, and to Nick
--
Kay