evapotranspiration on fine off-set weather station

[Francesco Scaramella]

Hello I have a question for all users of weewx: I own of fine-offset weather stations that make available the data of solar radiation and ev and when I have this type of sensors I have among the parameters also published that of evapotranspiration, but the I always find zero. What one knows how this parameter is generated and if there are any adjustments to be made for this brand of stations??
Francesco

[Thomas Keffer]

To calculate ET, you need outside temperature, outside humidity, radiation, and wind speed, for the last hour. Check your database to make sure they are all there.

On Tue, Feb 18, 2020 at 3:20 AM Francesco Scaramella <scaram...@gmail.com> wrote:

Hello I have a question for all users of weewx: I own of fine-offset weather stations that make available the data of solar radiation and ev and when I have this type of sensors I have among the parameters also published that of evapotranspiration, but the I always find zero. What one knows how this parameter is generated and if there are any adjustments to be made for this brand of stations??
Francesco

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[Francesco Scaramella]

The station certainly that is complete with all these parameters. I don't understand what kind of check I should do on the DB. There weren't all the paramenters I don't think I can post everything in the right way. I didn't understand anything in the answer.
Thank you

Il giorno martedì 18 febbraio 2020 13:39:03 UTC+1, Thomas Keffer ha scritto:

To calculate ET, you need outside temperature, outside humidity, radiation, and wind speed, for the last hour. Check your database to make sure they are all there.

On Tue, Feb 18, 2020 at 3:20 AM Francesco Scaramella <scaram...@gmail.com> wrote:

Hello I have a question for all users of weewx: I own of fine-offset weather stations that make available the data of solar radiation and ev and when I have this type of sensors I have among the parameters also published that of evapotranspiration, but the I always find zero. What one knows how this parameter is generated and if there are any adjustments to be made for this brand of stations??
Francesco

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[Thomas Keffer]

Take a look in your database. To find your database, consult the section Where to find things in the User's Guide.

sqlite3 weewx.sdb

sqlite> select datetime(dateTime,'unixepoch','localtime'), outTemp, outHumidity, radiation, windSpeed from archive where dateTime >= strftime('%s','now') - 3600;

This should show something like:

2020-02-25 15:05:00|50.3|58.0|168.0|0.0
2020-02-25 15:10:00|50.4|57.0|222.0|1.0
2020-02-25 15:15:00|50.4|58.0|196.0|1.0
2020-02-25 15:20:00|50.4|58.0|158.0|1.0
2020-02-25 15:25:00|50.3|58.0|137.0|1.0
2020-02-25 15:30:00|50.3|57.0|158.0|1.0
2020-02-25 15:35:00|50.3|58.0|165.0|1.0
2020-02-25 15:40:00|50.3|59.0|113.0|1.0
2020-02-25 15:45:00|50.0|58.0|110.0|1.0
2020-02-25 15:50:00|50.1|58.0|116.0|0.0
2020-02-25 15:55:00|50.2|60.0|111.0|1.0

If any value is missing, then you do not have enough data to calculate ET for the last hour.

-tk

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[Jim Pace]

I've never had anything but a zero for ET. All the required sensors are read and daily high/lows are reported. Have not yet looked in the db but wonder why a required entry would be missing.

[Tom Keffer]

In weewx.conf, make sure your section [[Calculations]] has an entry for ET:

  [[Calculations]]

    ... (other entries)

    ET = prefer_hardware

-tk

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[Jim Pace]

Just as I was going to check the db for the entries you said, my Weatherflow station started having radiation and windspeed sensor fails. Now that I have a replacment up and running, I did the db check and I do have all the parameters in there as well as ET calculations but the result is so small(in the 0.001 range) that Weewx rounds down to zero it appears. What numbers should I expect here in the Willamette Valley this time of year?

On Tuesday, February 18, 2020 at 3:20:23 AM UTC-8, Francesco Scaramella wrote:

[Tom Keffer]

It should be numbers like 0.01 or 0.02 inch per hour. I'm just around the corner in Hood River, and my max value today was 0.024/hr, but it is probably a bit drier here (RH today was 25%). So, if you have a 5 minute archive interval, 0.001 sounds about right.

ET is best viewed as summed over a day. I know the Seasons skin doesn't do that, but it really should. 

-tk

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