Why is gh-surface null for my location?

windyignis

Dear community,
I'm using the Windy Point Forecast API to obtain info about several locations. Everything is going great, and the community posts are very helpful. However, I'm having a problem and I don't seem to find a solution in previous posts.

The problem is I'm trying to obtain the gh parameter at given levels for a given location. This is my request body:
{
"lat": 38.0219,
"lon": -1.5,
"model": "gfs",
"parameters": ["gh"],
"levels": ["surface", "1000h"],
"key": "myKey"
}

So the gh-1000h results are fine, but for gh-surface I get a list of null. Why is this happening?

Thank you in advance.

idefix37

@windyignis
Hi, I’m not a Windy API specialist. I understand that you want to obtain the geopotential height at different levels, for example at 1000hPa level. This means that the geopotential height is the level where you get a 1000hPa pressure. Ok, but what is the meaning of geopotential height "at the surface"? I find the concept very strange and don't understand why Windy gives gh at surface as isolines.

windyignis

@idefix37 Thank you for your answer. I guess that, because of this uncertainity of meaning, the values are set to null. However, I don't get why the option is available, then.

Korina

@windyignis We will look into this, thank you.

Korina

@windyignis @idefix37 Hello, as mentioned in the API documentation " If the value is null, it means that the forecast model has no value for the given time, position and parameter.". Therefore your request does not work as anticipated.

idefix37

@korina
Actually I was referring to the website, more than to the API. In the website there are Geopotential heights shown when the altitude slider is set at surface. Which is not understandable.
Looking in detail to the gh depending on the pressure level, it can be at a location:
Slider set at 750m 925hPa —> gh 780m
Slider set at 600m 950hPa —> gh 570m
Slider set at 100m. ……………—> gh 570m
Slider set at surface………….—> gh 570m

It’s quite clear that the website shows, at 100m and at surface, the same gh value as at 950hPa.
It would be better that the gh isolines switch automatically to isobars at 100m and at surface.

Korina

@idefix37 Yes, it is a little confusing, but the parameter itself gh-surface does not exist.

windyignis

@korina thank you for your explanation. However, in Point Forecast API docs I can see that the variable gh accepts surface as a correct level. This is confusing, because if this level does not exist for this variable, then it shouldn't be present in the docs as available "(...) it is applicable for the following parameters: wind, dewpoint, temp, gh and rh (...) The allowed values are: surface, 1000h, (...)"

nesro

Hi @windyignis

Thanks for letting us know. This will be fixed in the next api update.

Tomas

windyignis

@windyignis Another thing I noted is that arome model does not support level parameters. This is also unclear in point forecast api docs, i had to search through the forum to discover that arome 0.01º is used and does not support level parameters. If you could let this be known in a single documentation for the API I think it would be more clear to understand. Thank you for your kind answers and support!