• Re: Ground temperature

    I repeat my suggestion/request for ground temperature at 10cm aka grass temperature. My potato plants suffered from ground frost while temp at 1m was 4°C.

  • Sailor Moderator

    Windy visualizes data from weather models and I am not sure that these models provide a temperature prediction at 10cm above ground surface. Then if you consider the resolution of the models that Windy shows in your region, a 10cm-temperature will not be very reliable when the resolution is about 10km and the risk of frost depends on topography and other local factors.

    Windy gives you the possibility to make your own assessment for the risk of frost. This risk depends on:
    Temperature: air temperature at 2m
    Humidity: air with high content of water vapor prevents quick night cooling, because it reduces the infrared radiation from the ground.
    Dew point: it is the temperature at which the dew forms. The lower this temperature is predicted, the higher is the cooling expected. If this temperature is negative, the risk of freezing will be really high.
    Clouds: cloudiness reduces the infrared radiation from the ground and thus the risk of frost. Clear sky at night increases the risk of frost.
    Cloud height: low clouds are more efficient to reduce to risk of frost than high clouds.
    Wind: the wind blows the cold air near the soil, mix it with the layers above and decreases the risk of frost.

    All these parameters are provided by Windy, as a layer and also in the Meteogram for a given location.
    So you can try to make your own assessment using these parameters.


  • GFS and other forecast models provide well such a parameter (and even more).
    Moreover, many other derived calculated parameters may be computed from available parameters.
    I guess Windy simply made a selection of most "popular" parameters, in order to avoid too much long lists. As models may contain hundreds of parameters/levels and while most of them are only used by forecasters, I would say this is the right choice.
    For "grass level" temperature, see e.g. this site:

  • Sailor Moderator

    Yes Mate, and what is the accuracy of a 22km resolution for grass temperature?

  • I would say ground temperature should have same accuracy as at 2 meters above the grass (then maybe @FransBetsy has enough big potatoes yard :o)))
    Otherwise, better accuracy (and not only for "grass" temperature) can be found on local models (with resolutions up to maximum a couple of km).

  • Sailor Moderator

    The parameter that you mention is the soil temperature between 0 and 10cm depth. So nothing to do with the air temperature above the ground surface or grass temperature.

  • Original post above said: "My potato plants suffered from ground frost while temp at 1m was 4°C".
    Thus I would say both surface temperature (+2m) and all those "ground" temperatures ("grass" was a joke :o) could get conjointly useful enough info to protect potatoes (and all of them with the same accuracy :o)))

  • Sailor Moderator

    Never mind you will not convince me.

    And for your information grass temperature is not a joke.

    @FransBetsy said in 10cm temperature:

    Re: Ground temperature
    I repeat my suggestion/request for ground temperature at 10cm aka grass temperature.

    Weather On Line has probably developed their own « cocking recipe » using the factors I explained in my first post. Windy visualizes raw data from weather models, only. The do not develop their own algorithm, as far as I know.

  • Hey, these grass temperatures are observed values, collected by specific sensors; they are not computed in weather forecast models like GFS, with worldwide coverage, my poor "grass" joke was related to.

    I guess @FransBetsy's requirement was about displaying on maps such a "grass" temperature for next days, not for real-time or past observations. I think farmers generally need forecast weather in order to protect their plants, instead real-time observations. For real time grass temperature, they could just deploy on the grass a couple of such a sensors (a priori @FransBetsy has such a temperature sensor at +1m level), and would not need to read values on Windy maps (even if Windy allows displaying observed values for personal weather stations, too).

    Anyway, very specialized agricultural weather forecast at grass level and at very high resolutions exists, and even for each type of plant, but they cannot have worldwide coverage (and they are expensive enough, too).

    What I said is that an indicator for such a "grass" temperature forecast could be computed from models, by taking into account a couple of pertinent parameters (e.g. the three or more ground temperatures, +2m temperature, wind at +10m, dew point temperature, pressure, solar radiation, precipitations, etc.). I'm sure such an algorithm could be found in literature, as specific weather forecasts are well generated by met offices for agriculture. I cannot see specific grass level temperature forecast made by WeatherOnLine, as this is not free (this is kinda proof that they don't simply collect values from free forecast models).

    What I also said is that I guess Windy made the choice to not display all available parameters in forecast models, as many of them are only used by professional forecasters or researchers and parameter lists would be too long for the general public. I don't know if Windy plans are to display more parameters from forecast models or to compute derived parameters; I guess it depends on users request and feedback (and a lot on the available development resources they have).

  • Sailor Moderator

    Your long speech teaches me nothing. That’s exactly what I've explained so far. Next time give that kind of explanation to the person asking a question not to me.

  • I apologize if I annoyed anyone with boring speech above.
    Its purpose was not to teach - I'm not a teacher - I was just trying to help (the community, not knowledge people who surely know the whole holy stuff better than me).
    I also noted the remark.

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