Addition to WC ET Report for Soil sensor data.

[elagache]

Dear WeatherCat fans, 

I've made an offer to Steve to add one more feature into my WC ET Reporter script which would collect data from his Leaf & Soil Moisture/Temperature probes that he has on loan from Davis.

We've exchanged some email and it just isn't clear how to use the leaf data.  I suspect this is intended mostly for tree orchards rather than gardens and the main purpose is monitoring conditions that can really damage fruit/nut trees.  However, Steve has identified possible uses for the soil data.

So I would like to propose the following modest addition.  Have the script create a new file of data that can be exported into a spreadsheet with the following tab-delimited data:

• Davis VP-2 estimate of Evapotranspiration (needed to compute moisture losses)
• The average soil temperature during the past 24 hours.
• The minimum soil moisture during the past 24 hours

My thought is to have these values computed and appended to the file at midnight just as the script does its evapotranspiration calculations now.  The file would be like the existing files for ET with the date in the first column in a format that at least Excel can decode.

Steve has found some sources that would allow him to compute how much to water given this information, so that would seem to be a useful way to put his new sensors to work.

Any thoughts from you'all? Anything else that would be good to add?

It isn't a difficult addition to provide, but I would prefer not to have to do this twice! 

Cheers, Edouard 

[Steve]

Thank you, Edouard.

I think the proposed additions make sense as I understand it right now. Are you going to include this in both ET calculations, or just the VP2 one? Here's my comparison of ET calculated with both the B-C and VP2 formula since November.





I'm not at all sure what to do with the Leaf Wetness. It can be used with Davis' Ag/Turf software (Windows only) but I certainly don't need that. What I've found it good for so far is a great early rain warning! It jumps right up if there's a mist or very light rain that might take some time to register on the tipping bucket mechanism of the ISS. A guy on the WXforum (where I've cross-posted my review) says he uses it in conjunction with the temp and dew point to predict frost and fog.

Here's a link to my temporary graph of the output from the Leaf & Soil Station. The red line is the Leaf Wetness, which goes from zero (dry) to 15 (wet), the blue is the Soil Temperature at 10" depth, and the green is the Soil Moisture at 10" depth. That scale is from zero (soaking wet) to 200 (bone dry)

http://www.avon-weather.com/soil.html

Steve

[elagache]

Howdy Steve and WeatherCat gardeners

I think the proposed additions make sense as I understand it right now. Are you going to include this in both ET calculations, or just the VP2 one?

I had been thinking only to include the VP-2 ET calculation because it is much more accurate and I can't imagine someone would buy the soil sensors without already having the radiation sensor.

Here's my comparison of ET calculated with both the B-C and VP2 formula since November.

Thanks for sharing your data.  It is similar to what I've seen here in wintertime.  The Blaney?Criddle estimate only works well when evapotranspiration is driven mostly by direct solar heating that also is causing the observed temperatures.  When the winds kick up or there is higher humidity, the Blaney?Criddle estimate started to go off.  Also, when solar radiation is weaker, it tends to overestimate the evapotranspiration.   As reported, it is best used only in arid areas like the American southwest.  Still, I hoped it would be a guide for folks who can't afford a Davis station and radiation sensor.

What I've found it good for so far is a great early rain warning! It jumps right up if there's a mist or very light rain that might take some time to register on the tipping bucket mechanism of the ISS. A guy on the WXforum (where I've cross-posted my review) says he uses it in conjunction with the temp and dew point to predict frost and fog.

I've complained about the slow response to misty, foggy condition by most weather stations.  Even if the rain bucket doesn't tip, the moisture on the ground could be a serious safety hazard.  Too bad Davis didn't adapt this sensor into something that could be added to the VP-2 to detect this sort of mist without all the overhead of soil and leaf sensors.

I was wondering about adding one more entry to my proposed spreadsheet output: maximum soil moisture.  The case I was wondering about is what happens if you water the area during the day.  In that case, you might want to make sure that the soil reached the target moisture content.

So that's where my thinking is on this right now.

Cheers, Edouard 

[elagache]

Howdy Steve and WeatherCat fans, 

There was no time like the present so I've mocked up the changes to WC ET Reporter so that it can produce the spreadsheet I've sketched out.  I'm feeding it outside temperature data for testing purposes and will see if the script behaves as promised.

I'll keep you'all posted!!

Cheers, Edouard 

[Steve]

Thanks Edouard,

Yes, I think the VP2's ET must reflect better. I'd noticed several times when it was cool and overcast that the VP2's ET was zero and the C-T had some higher reading, so I was already sort of discounting that one.

Adding Maximum Soil Moisture makes sense, as it will reflect watering of the gardens. I hadn't thought that far ahead.

Thanks again,
Steve