Topic: Best rain gauge for morning dew.

[tdhcsc]

I live in Southern California on the coast.  It doesn't rain rain very often but being at the beach we have a lot of dew.  Even though it doesn't rain, everything is very wet most mornings.  I'd like a rain gauge that is good at measuring the extremely small amounts of precipitation (or dew) we wake up to each morning.

After considering different weather stations, at the moment I'm gravitating toward the Davis Vantage Pro 2 and was wondering if the included rain gauge is capable of recording such small amounts or if a different weather station or alternate rain gauge would be a better choice.

A different note.
I'm a retired sailor and have just wired an old Raymarine windpoint/windspeed system at the house.  It's still not finished but's working great giving me very fast wind reading updates with dampening capable anywhere from 1/4 second to 10 seconds.  At present it's set at 1 second.  Really cool & reminds me of our now sold sailboat.  Now for the rest of the system and a very sensitive rain collector would be great.

Photo, Raymarine windpoint/windspeed in a cardboard box on the refrigerator. The bow of the boat on the gauge is the direction your facing.  The compass rose is just a cutout and taped on for direction purposes.  Perhaps next week I'll install it correctly.

[ValentineWeather]

The Davis won't tip until .01. I've had it happen before after a couple really damp mornings but its not common, more likely what dew gets collected will evaporate before tipping the bucket.

[SLOweather]

I was not aware of anything made to measure dew. In my head I contrived a scale based unit that would weigh a panel and measure the accumulation of dew. Then I Googled measuring dew. All the good ideas have apparently already been "thunk".

From Wikipedia's article on dew:

Measurement

A classical device for dew measurement is the drosometer. A small, artificial condenser surface is suspended from an arm attached to a pointer or a pen that records the weight changes of the condenser on a drum. Besides being very wind sensitive, however, this, like all artificial surface devices, only provides a measure of the meteorological potential for dew formation. The actual amount of dew in a specific place is strongly dependent on surface properties. For its measurement, plants, leaves, or whole soil columns are placed on a balance with their surface at the same height and in the same surroundings as would occur naturally, thus providing a small lysimeter. Further methods include estimation by means of comparing the droplets to standardized photographs, or volumetric measurement of the amount of water wiped from the surface. Some of these methods include guttation, while others only measure dewfall and/or distillation.

Now, then... You could figure out a larger area with more slope and feed that into a raingauge. However, my experience this morning with the shade tarp over the chicken coop says it'll have to be pretty steep to get the dew to flow, or be mechanically shaken in some way. The dew forms little beads that need encouragement to flow together.

I don't believe the Hydreon optical rain gauges, RG11s, will quantitatively measure dew, but they dew have a condensation mode that will close the relay on detected condensation, although I've never tried it.

The wireless Davis Leaf Wetness Station will detect dew on a unitless scale of 0 (dry) to 15 (wet). Here's our home station's graph from the last 24 hours:

[tdhcsc]

I think thats my answer.  Didn't even know it existed.

Thanks.

[SLOweather]

Fine business. I'm glad to help. You can get the best prices on Davis only by asking the dealer for them, registering on their site, or calling on the phone. Davis won't let them advertise as low as they will sell. I get everything from Rob at Rainmanweather.com.

I think thats my answer.  Didn't even know it existed.

Thanks.

[tdhcsc]

I've been doing research on the Leaf Moisture Detector system but can't find information I need.  Since you had one set up I've got a question on what I need to make the system work and where the graph is.

OK, I need the Leaf Moisture Detector & the transmitter.  Since my wife's hobby is exotic palms I'll probably get a couple of Soil Moisture sensors.  After researching I'm a bit confused.  Does the graph and other information display somewhere on the VantagePro2 or do I need to purchase other items as well?  Davis isn't very clear on that issue, at least not in the installation manual but seems to suggest I need more stuff than just the 2 components and a bit of configuration.

Thanks for any help.

Dan

[SLOweather]

Hi Dan,

First, the idiosyncrasies of the leaf wetness/soil moisture station. You can have a single fully-populated station with 2 Leaf Wetness Sensors , 4 Soil Moisture Sensors, and 4 Temperature Probes on a system, or two partially-populated stations, one with 2 leaf wetness sensors and 2 temperature probes, and the other with 4 soil moisture sensors and 4 temperatures probes.

In either case, the stations don't have to be fully populated per the rules to work. For instance, I have one 4 t x 4 sm soil station, and one leaf station with only one leaf wetness sensor, and one temp sensor which I stick in the compost pile.

I tell you this so you know what to purchase. Generally you bury one temp sensor with each moisture probe so the console will temperature compensate the moisture reading.

Next, I believe the console will show the wetness and moistures on the little graph when the appropriate buttons are pressed.

Then, you can get a WeatherLink package which will connect your console to your computer and includes software. I don't use weatherlink software, so I can't speak to its ability to graph leaf wetness.

The graph you saw came from our home station's WeatherElement page, http://www.weatherelement.com/teddybearoaks. Actually, that graph is on the More Graphs page, http://www.weatherelement.com/teddybearoaks/Graphs at the bottom left.

WeatherElement uses a Davis Serial WeatherLink to connect to a WeatherElement Data Hub which then sends the data to the WeatherElement server for archiving, display and graphing.

Please let me know if you have any questions.

Chris

[Bushman]

Vaisala makes some.  But if you have to ask the price.... 

[ocala]

FWIW I have recorded dew in my cocorahs gauge.
For the OP, that is a plastic rain gauge. Here's a pic.

[Skywatch]

Suppose one could take a sheet, string it between 4 posts and place a rock in the center, then place a gauge below it. Of course the size of sheet would have to be factored in. Or retrofit the gauge with a larger funnel coated with a hydrophobic surface so the little droplets roll in.

[Bushman]

Here's an interesting take on plant monitoring:  http://rapi-projects.de.vu/