When people talk about x hours of continuous frost (we've just 111
hours followed a few hours later by another 90) I've always assumed
that this statement means that the temperature is beneath 0C in ALL
that period.

But then what is a frost hour (as in reporting to COL)? I've taken that
to be an hour in which there is a frost (i.e. temperature beneath 0C at
SOME point).

So there are two different measures of hourly frostiness: one in which
the temperature is beneath 0 all hour, the other where the temperature
falls beneath 0 at some point. This appears to lead to an ambiguity in
the way the total number of frost hours in a month is reprorted.

--

Trevor
Recovering in Lundie, near Dundee
http://www.personal.dundee.ac.uk/~taharley/

Trevor Harley wrote:



When people talk about x hours of continuous frost (we've just 111 hours
followed a few hours later by another 90) I've always assumed that this
statement means that the temperature is beneath 0C in ALL that period.

But then what is a frost hour (as in reporting to COL)? I've taken that to be
an hour in which there is a frost (i.e. temperature beneath 0C at SOME point).

So there are two different measures of hourly frostiness: one in which the
temperature is beneath 0 all hour, the other where the temperature falls
beneath 0 at some point. This appears to lead to an ambiguity in the way the
total number of frost hours in a month is reprorted.

It should be the total duration below zero, not the number of clock hours
within which the temp was below zero at some time.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.

"Norman" wrote in message
...
Trevor Harley wrote:



When people talk about x hours of continuous frost (we've just 111 hours
followed a few hours later by another 90) I've always assumed that this
statement means that the temperature is beneath 0C in ALL that period.

But then what is a frost hour (as in reporting to COL)? I've taken that
to be
an hour in which there is a frost (i.e. temperature beneath 0C at SOME
point).

So there are two different measures of hourly frostiness: one in which
the
temperature is beneath 0 all hour, the other where the temperature falls
beneath 0 at some point. This appears to lead to an ambiguity in the way
the
total number of frost hours in a month is reprorted.

It should be the total duration below zero, not the number of clock hours
within which the temp was below zero at some time.

--

Norman's is the way I've always interpreted it. An early version of Davis
Weatherlink had an add-on which you could set up to do this automatically.
However this option is no longer there so I simply do it from the records-as
long as your archive interval is not too large of course. Doesn't take much
time.

--
George in Epping, West Essex (107m asl)
www.eppingweather.co.uk
www.winter1947.co.uk
COL 36055

Perhaps a better terminology would be frost duration, that is the total
duration when the air temperature is below 0.0C. When I used a standard
thermogaph to record temperature continuously, I used a scaled magnifier to
obtain the duration of frost. Nowdays I use the AWS data, which consists of
one minute average air temperature, thus my frost duration is now simply the
number of minutes with air temp below 0.0C (divided by 60 for COL).

--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
www.woksat.info/wwp.html

"Trevor Harley" wrote in message
news:2010121012190716807-taharley@dundeeacuk...


When people talk about x hours of continuous frost (we've just 111 hours
followed a few hours later by another 90) I've always assumed that this
statement means that the temperature is beneath 0C in ALL that period.

But then what is a frost hour (as in reporting to COL)? I've taken that to
be an hour in which there is a frost (i.e. temperature beneath 0C at SOME
point).

So there are two different measures of hourly frostiness: one in which the
temperature is beneath 0 all hour, the other where the temperature falls
beneath 0 at some point. This appears to lead to an ambiguity in the way
the total number of frost hours in a month is reprorted.

--

Trevor
Recovering in Lundie, near Dundee
http://www.personal.dundee.ac.uk/~taharley/

On 2010-12-10 15:18:03 +0000, "Bernard Burton"
said:

Perhaps a better terminology would be frost duration, that is the total
duration when the air temperature is below 0.0C. When I used a standard
thermogaph to record temperature continuously, I used a scaled magnifier to
obtain the duration of frost. Nowdays I use the AWS data, which consists of
one minute average air temperature, thus my frost duration is now simply the
number of minutes with air temp below 0.0C (divided by 60 for COL).

--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
www.woksat.info/wwp.html

"Trevor Harley" wrote in message
news:2010121012190716807-taharley@dundeeacuk...


When people talk about x hours of continuous frost (we've just 111 hours
followed a few hours later by another 90) I've always assumed that this
statement means that the temperature is beneath 0C in ALL that period.

But then what is a frost hour (as in reporting to COL)? I've taken that to
be an hour in which there is a frost (i.e. temperature beneath 0C at SOME
point).

So there are two different measures of hourly frostiness: one in which the
temperature is beneath 0 all hour, the other where the temperature falls
beneath 0 at some point. This appears to lead to an ambiguity in the way
the total number of frost hours in a month is reprorted.

--

Trevor
Recovering in Lundie, near Dundee
http://www.personal.dundee.ac.uk/~taharley/



Thanks everyone. That makes sense.
Trevor

I've just been looking into how best to calculate my frost duration. I have my archive interval set to every 10 minutes. If at any point during the interval the temp drops below 0 would it be acceptable to add the 10 minutes to my frost duration? I have my interval set at 10 minutes so I can calculate average 10 min wind speed.

Thanks,

Luke

On Friday, 10 December 2010 12:19:07 UTC, Trevor Harley wrote:
When people talk about x hours of continuous frost (we've just 111
hours followed a few hours later by another 90) I've always assumed
that this statement means that the temperature is beneath 0C in ALL
that period.

But then what is a frost hour (as in reporting to COL)? I've taken that
to be an hour in which there is a frost (i.e. temperature beneath 0C at
SOME point).

So there are two different measures of hourly frostiness: one in which
the temperature is beneath 0 all hour, the other where the temperature
falls beneath 0 at some point. This appears to lead to an ambiguity in
the way the total number of frost hours in a month is reprorted.

--

Trevor
Recovering in Lundie, near Dundee
http://www.personal.dundee.ac.uk/~taharley/

I've just been looking into how best to calculate my frost duration. I have my archive interval set to every 10 minutes. If at any point during the interval the temp drops below 0 would it be acceptable to add the 10 minutes to my frost duration? I have my interval set at 10 minutes so I can calculate average 10 min wind speed.

wrote in message
...
I've just been looking into how best to calculate my frost duration. I have
my archive interval set to every 10 minutes. If at any point during the
interval the temp drops below 0 would it be acceptable to add the 10 minutes
to my frost duration? I have my interval set at 10 minutes so I can
calculate average 10 min wind speed.

Thanks,

Luke


Luke, frost duration used to be obtained by reading off a graphical record,
as from a bi-metallic thermogram. With the advent of the digital age, then
it became feasable to obtain a more accurate reading by adding up all the
minutes when the air temperature is below 0.0C. In my own case, I use a one
minute sampling period, and store the data in a one minute data set. I think
that you will get only an approximate indication of frost duration if you
use a 10 minute data interval, and as you say, problems arise when you try
to guess what portion of a 10 minute period had an air frost. I would advise
using a one minute sampling period, and post calculate your 10 minute wind
average from that. My anemometer outputs one second data, and I convert that
to a one minute average, and calculate the 10 minute average when needed
from the one minute data.

--
Bernard Burton

Satellite images and weather data for Wokingham at:
www.woksat.info/wwp.html



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On Friday, 2 December 2016 10:51:39 UTC, Bernard Burton wrote:
wrote in message
...
I've just been looking into how best to calculate my frost duration. I have
my archive interval set to every 10 minutes. If at any point during the
interval the temp drops below 0 would it be acceptable to add the 10 minutes
to my frost duration? I have my interval set at 10 minutes so I can
calculate average 10 min wind speed.

Thanks,

Luke


Luke, frost duration used to be obtained by reading off a graphical record,
as from a bi-metallic thermogram. With the advent of the digital age, then
it became feasable to obtain a more accurate reading by adding up all the
minutes when the air temperature is below 0.0C. In my own case, I use a one
minute sampling period, and store the data in a one minute data set. I think
that you will get only an approximate indication of frost duration if you
use a 10 minute data interval, and as you say, problems arise when you try
to guess what portion of a 10 minute period had an air frost. I would advise
using a one minute sampling period, and post calculate your 10 minute wind
average from that. My anemometer outputs one second data, and I convert that
to a one minute average, and calculate the 10 minute average when needed
from the one minute data.

--
Bernard Burton

Satellite images and weather data for Wokingham at:
www.woksat.info/wwp.html



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Thanks for your response Bernard. So the best way would be to total up the one minute wind speed samples and divide by 10 to obtain a 10 min average?

Thanks,

Luke