Circle

Basic Example

An example of a circle requested via earthkit-data:

import earthkit.data

request = {
    "class": "od",
    "stream" : "enfo",
    "type" : "pf",
    "date" : -1,  # Note: date must be within the last two days 
    "time" : "0000",
    "levtype" : "sfc",
    "expver" : "0001", 
    "domain" : "g",
    "param" : "164/167/169",
    "number" : "1/to/50",
    "step" : "0",
    "feature" : {
        "type" : "circle",
        "center": [[-9.10, 38.78]],
        "radius": 0.1,
    },
    "format": "covjson",
}

ds = earthkit.data.from_source("polytope", "ecmwf-mars", request, stream=False, address='polytope.ecmwf.int')

The following will return a circle centered at the point provided with a radius of 0.1 in degrees, starting yesterday at 00Z with step 0, for the parameters 164/167/169 at the point given. This data will be returned for each ensemble number requested.

"polytope" refers to the underlying service being used to return the data. "ecmwf-mars" is the dataset we are looking to retrieve from. Setting stream=False returns all the requested data to us once it is available. address points to the endpoint for the polytope server.

Required Fields

For a circle within the feature dictionary three fields are required

• type
• center
• radius

For a circle type must be circle.

center must be a nested list with a point containing a latitude and a longitude.

radius refers to the radius of the requested circle in the form of degrees and is a single value.

Optional Fields

axes can also be provided which defines the spatial axes on which the request is made. For example if the user provides points in the order longitude, latitude they can add axes : ["longitude", "latitude"].