Dew, frost melt and "rain days"
 

A large portion (8/23) of the "rain days" I recorded in October were due to dew or frost melt. My question is - should they count towards the "rain days" total for the month? It has been a fairly dry October here in the Rhondda (190 mm - 73% of the eLTA) and I think that 23 "rain days" is unrepresentative.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement currently)
Stats for the month so far: https://www.hosiene.co.uk/weather/st...201810OCT.xlsx

Dew, frost melt and "rain days"
 

Freddie wrote:

A large portion (8/23) of the "rain days" I recorded in October were
due to dew or frost melt. My question is - should they count towards
the "rain days" total for the month? It has been a fairly dry
October here in the Rhondda (190 mm - 73% of the eLTA) and I think
that 23 "rain days" is unrepresentative.

If the total from dew/frost melt is 0.2mm or more for the day then I
think that does count as a rain day, though I could be wrong!

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

Dew, frost melt and "rain days"
 

Freddie,
You need to decide if it is the frost/dew that is causing the total, or if
it is condensation. At my station, plastic raingauges produce copious
amounts of condensation on days when the 5 inch copper gauge is dry both
inside and out. Also, a 0.2 mm TBR may give a tip and show 0.2 mm when much
less 'dew/frost' has been added to a nearly full bucket. Personally, I
disregard dew/frost in my rainfall returns unless there is evidence in the
5" gauge. It is also likely that most of the dew/frost that does occur is
evaporated (recycled) precipitation from the local area which will have
already been measured when it fell.

--
Bernard Burton

Satellite images and weather data for Wokingham at:
www.woksat.info/wwp.html
"Freddie" wrote in message
...
A large portion (8/23) of the "rain days" I recorded in October were due to
dew or frost melt. My question is - should they count towards the "rain
days" total for the month? It has been a fairly dry October here in the
Rhondda (190 mm - 73% of the eLTA) and I think that 23 "rain days" is
unrepresentative.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement
currently)
Stats for the month so far:
https://www.hosiene.co.uk/weather/st...201810OCT.xlsx



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Dew, frost melt and "rain days"
 

On Thursday, 1 November 2018 15:32:24 UTC, Bernard Burton wrote:
Freddie,
You need to decide if it is the frost/dew that is causing the total, or if
it is condensation. At my station, plastic raingauges produce copious
amounts of condensation on days when the 5 inch copper gauge is dry both
inside and out. Also, a 0.2 mm TBR may give a tip and show 0.2 mm when much
less 'dew/frost' has been added to a nearly full bucket. Personally, I
disregard dew/frost in my rainfall returns unless there is evidence in the
5" gauge. It is also likely that most of the dew/frost that does occur is
evaporated (recycled) precipitation from the local area which will have
already been measured when it fell.
Thanks Bernard.
I believe it is all due to dew and/or frost, as there was no precipitation on the days in question, and the tips all occurred between 0700z-0900z. There is the possibility that some of the water contained in the bucket on some of the occasions was due to previous precipitation - but I noted that on all occasions there was either heavy dew or moderate frost deposits. My location is in the bottom of a steep-sided valley (the sides are 500-1000 feet above the valley floor) near a river, so is prone to cold still nights and consequent liquid deposits.
I will take your advice and disregard those tips that I'm certain are down to dew and/or frost.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement currently)
Stats for the month so far: https://www.hosiene.co.uk/weather/st...201810OCT.xlsx

Dew, frost melt and "rain days"
 

On 01/11/2018 10:57, Freddie wrote:
A large portion (8/23) of the "rain days" I recorded in October were due to dew or frost melt. My question is - should they count towards the "rain days" total for the month? It has been a fairly dry October here in the Rhondda (190 mm - 73% of the eLTA) and I think that 23 "rain days" is unrepresentative.

My Davis TBR frequently gives daily 0.2 mm tips, sometimes 0.4 mm if the
dew is particularly heavy whilst my copper 5" rain gauge remains bone dry.

The large plastic funnel of the Davis TBR seems to be a big condensation
trap. I use the copper gauge for calculating actual 'rain' and 'wet'
days and ignore the Davis TBR otherwise nearly every day last week would
have been a 'rain' day.

--
Nick Gardner
Otter Valley, Devon
20 m amsl
http://www.ottervalleyweather.me.uk

Dew, frost melt and "rain days"
 

This puzzles me, as I would imagine the copper of a standard rain gauge would become much cooler than the plastic of a Davis rain funnel, and consequently experience more condensation.

--
Freddie
Ystrad Rhondda

Dew, frost melt and "rain days"
 

Freddie wrote:

This puzzles me, as I would imagine the copper of a standard rain
gauge would become much cooler than the plastic of a Davis rain
funnel, and consequently experience more condensation.

The funnel of my VP2 often seems to be wetter than the copper gauge on
dewy mornings. I use the copper gauge for my records. I use the
measurements from the VP2 to apportion the total amount captured in the
copper gauge into daily totals days anytime that I am away for two or
more days.

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