Cumulus Support

Hi Guys

I had a hard frost last night and the Dew from that showed up as 0.4mm rainfall. I was wondering is there any way to amend these readings in Cumulus or in the Davis Vantage Vue console??? I don't want today showing rainfall when it was a clear sunny day. Tia

Mike

mickopla wrote:Hi Guys

I had a hard frost last night and the Dew from that showed up as 0.4mm rainfall. I was wondering is there any way to amend these readings in Cumulus or in the Davis Vantage Vue console??? I don't want today showing rainfall when it was a clear sunny day. Tia

Mike

Mike,

I have the same thing on my VP2 and after some thought decided it is a valid measurement. The rain gauge is for measuring precipitation - not just rainfall. Technically dew IS precipitation so the reading is valid. It shows you have good kit for it to be that sensitive.

As I understand it, in UKMO reporting, the correct thing to do is include dew/frost etc in the rainfall totals, but to make an appropriate comment in the register. How you interpret this, or indeed whether you want to, not being in the UK, is up to you.

If you do want to remove it from the total, there is an entry in the FAQ with instructions.

We posted about what is a rain day a few weeks back.

"rain day—(Also called day of rain.) In British climatology, a period of 24 hours, normally commencing at 0900 UTC, in which at least 0.01 in. or 0.2 mm of precipitation is recorded.
It is the practice of the U.S. National Weather Service to use phrases that are more self-defining, such as “day with measurable precipitation” or “day with 0.01 inch or more” (of precipitation). "

Precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena) is any product of the condensation of atmospheric water vapor that falls under gravity

Interesting question.

Randy

I'm glad I found this thread as was about to post similar. I've noticed a fairly regular 0.2mm on clear nights which is definitely dew. As it is recognised precipitation I'll just move on, cheers

Our Weather Organisation here in Australia also counts dew as a rain day, anything over 0.2mm counts, 0.1mm or ground wet acts as a TRACE.

I do as Steve stated before and write if the 0.2 is dew or from fog.

Although 0.2 or 0.4mm evaporates within the hour when the sun is up

I've always left mine as rainfall. My manual gauge will collect moisture, as it is down near ground level and in the shade. I simply imagine that 0.2mm is soaking in the ground as if it were rainfall. It can be easy to get a bit pedantic over these discrepancies.

I also leave any dew reading in my tipping bucket rain totals. However in my CoCoRaHS reporting (daily precipitation manual reporting) I usually report as 0.0 if I know it is dew rather than actual rain, and err on the side of reporting precipitation if I am unsure. But I fret over it as it adds to number of rain days or shortens rain-free days.

Enjoying,
Paul