Extracting single point

Dear Rutger,

I have never used this particular data, do you have the CDS catalogue reference and maybe the Toolbox retrieve that you used so I can try things out?

I am surprised that the retrieved data is not in a regular grid which makes me think that the data is not Toolbox ready yet but I might be wrong on that.

ct.geo.extract_point does not work because the data does not have 'lat' and 'lon' as dimension. However extract_point has two keyword arguments "lon_dim" and "lat_dim" where you can specify which dimensions should be considered as lat and lon. In your case you could try:

ct.geo.extract_point(data, lat_dim='y', lon_dim='x', lat=757500.0, lon=2507500.0)

I have never tested this as I don't have the data to test it but it should work. Obviously specifying the location with x and y is not that handy but it might be better than nothing.

I hope some of this helps.

Vivien

Hi Vivien

I will try that solution, the challenge of course is to find the correct X/Y coordinates for my lon/lat of interest. 

The catalogue entry of the dataset is https://cds.climate.copernicus.eu/cdsapp#!/dataset/efas-historical?tab=overview and I will copy the Toolbox request below (which I based on the Toolbox request shown in the catalogue). 

data = ct.catalogue.retrieve(
'efas-historical',
{
'format':'netcdf',
'simulation_version':'version_3',
'variable':'snow_depth_water_equivalent',
'model_levels':'surface_level',
'hyear':'2012',
'hmonth':[
'january','february',
'march','april','may'
],
'hday':[
'01','02','03',
'04','05','06',
'07','08','09',
'10','11','12',
'13','14','15',
'16','17','18',
'19','20','21',
'22','23','24',
'25','26','27',
'28','29','30',
'31'
]
})

(Apologies, for whatever reason indentation is not preserved when I copy the code here). 

Thanks

Rutger

Incidentally, I get the same error message when I try it out with the UERRA dataset, with the following code:

 # Time range
data = ct.catalogue.retrieve(
'reanalysis-uerra-europe-single-levels',
{
'format':'grib',
'origin':'uerra_harmonie',
'variable':'snow_depth_water_equivalent',
'year':'2000',
'month':[
'01','02','03',
'04','05'
],
'day':[
'01','02','03',
'04','05','06',
'07','08','09',
'10','11','12',
'13','14','15',
'16','17','18',
'19','20','21',
'22','23','24',
'25','26','27',
'28','29','30',
'31'
],
'time':'12:00'
})


print(data)

data_sel = ct.geo.extract_point(data, lon=lon, lat=lat)

I get the following output:

<xarray.DataArray 'snow_amount' (time: 152, y: 565, x: 565)>
dask.array<shape=(152, 565, 565), dtype=float32, chunksize=(48, 565, 565)>
Coordinates:
    forecast_reference_time  (time) datetime64[ns] dask.array<shape=(152,), chunksize=(48,)>
    leadtime                 timedelta64[ns] ...
    surface                  int64 ...
    lat                      (y, x) float64 dask.array<shape=(565, 565), chunksize=(565, 565)>
    lon                      (y, x) float64 dask.array<shape=(565, 565), chunksize=(565, 565)>
  * time                     (time) datetime64[ns] 2000-01-01T12:00:00 ... 2000-05-31T12:00:00
Dimensions without coordinates: y, x
Attributes:
    long_name:      Snow Amount
    units:          kg m^-2
    standard_name:  surface_snow_amount
    cell_methods:   area: mean where land time: mean
    cell_measures:  area: areacella
    comment:        where land over land, this is computed as the mean amount...
    type:           real
    Conventions:    CF-1.7
    institution:    Norrkoping
    history:        2019-10-17T16:23:47 GRIB to CDM+CF via cfgrib-0.9.5.5/ecC...
    source:         UERRA-SINGLE_LEVELS

And then the following error:

Traceback (most recent call last):
  File "/opt/cdstoolbox/cdscompute/cdscompute/cdshandlers/services/handler.py", line 49, in handle_request
    result = cached(context.method, proc, context, *context.args, **context.kwargs)
(...)
  File "/usr/local/lib/python3.6/site-packages/xarray/core/indexing.py", line 207, in get_dim_indexers
    % invalid)
ValueError: dimensions or multi-index levels ['lon', 'lat'] do not exist

The problem seems similar in that lat, lon are coordinates but not dimensions, but here x and y are 'dimensions without coordinates' so I wouldn't immediately know how to go about referencing them.

Cheers!

Rutger

Dear Rutger,

I looked into the make_regular problem and the function is poorly documented and is missing two keyword arguments 'xref' and 'yref' in the documentation. This will be corrected.

This means you can actually use ct.geo.make_regular(data, xref='x', yref='y') on both UFAS and UERRA data you were trying to work with and get regular gridded data to work with. I have copied two examples of retrieve / make_regular / extract_point that worked for me. 

I did have a few Run time errors while I was testing, it might have to do with where the UERRA and EFAS data are pulled from as I have not experienced any similar errors working on other datasets lately. My advice with run time errors is to just try again.

import cdstoolbox as ct


@ct.application(title='Hello World!')
@ct.output.download()
def application():

    data = ct.catalogue.retrieve(
        'reanalysis-uerra-europe-single-levels',
        {
            'format':'grib',
            'origin':'uerra_harmonie',
            'variable':'snow_depth_water_equivalent',
            'year':'2000',
            'month':[
                '01',
            ],
            'day':[
                '01', '02'
            ],
            'time':'12:00'
        })

    data_reg = ct.geo.make_regular(data, xref='x', yref='y')
    
    data_point = ct.geo.extract_point(data_reg, lat=45.8326, lon=6.8652)
    
    print(data_point)
    return data_point

import cdstoolbox as ct


@ct.application(title='Hello World!')
@ct.output.download()
def application():

    data = ct.catalogue.retrieve(
        'efas-historical',
        {
            'format':'netcdf',
            'simulation_version':'version_3',
            'variable':'snow_depth_water_equivalent',
            'model_levels':'surface_level',
            'hyear':'2012',
            'hmonth':[
                'january',
            ],
            'hday':[
                '01','02',
            ]
        })
    
    data_reg = ct.geo.make_regular(data, xref='x', yref='y')
    
    data_point = ct.geo.extract_point(data_reg, lat=45.8326, lon=6.8652)
    
    print(data_point)
    return data_point

Thank you, Vivien! That seems to work indeed - and useful to know.

All the best

Rutger

Hello,

As a beginner in using the Toolbox editor I would like to ask a question about extracting data from an EFAS set for a specific point. For the following application I receive an error and I have difficulties in solving it. How can I solve it? 

Thank you.

import cdstoolbox as ct

@ct.application(title='Download data')
@ct.output.download()
def download_application():
data = ct.catalogue.retrieve(
'efas-forecast',
{
'originating_centre': 'ecmwf',
'product_type': 'high_resolution_forecast',
'variable': 'river_discharge_in_the_last_6_hours',
'model_levels': 'surface_level',
'year': '2021',
'month': '03',
'day': [
'01', '02', '03',
'04', '05', '06',
'07',
],
'time': '12:00',
'leadtime_hour': [
'0', '102', '108',
'114', '12', '120',
'126', '132', '138',
'144', '150', '156',
'162', '168', '174',
'18', '180', '186',
'192', '198', '204',
'210', '216', '222',
'228', '234', '24',
'240', '30', '36',
'42', '48', '54',
'6', '60', '66',
'72', '78', '84',
'90', '96',
],
}
)

data_reg = ct.geo.make_regular(data, xref='x', yref='y')

data_point = ct.geo.extract_point(data_reg, lat=44.8087, lon=21.3901)

return data_point

Traceback (most recent call last):
  File "/opt/cdstoolbox/cdscompute/cdscompute/cdshandlers/services/handler.py", line 55, in handle_request
    result = cached(context.method, proc, context, context.args, context.kwargs)
  File "/opt/cdstoolbox/cdscompute/cdscompute/caching.py", line 108, in cached
    result = proc(context, *context.args, **context.kwargs)
  File "/opt/cdstoolbox/cdscompute/cdscompute/services.py", line 118, in __call__
    return p(*args, **kwargs)
  File "/opt/cdstoolbox/cdscompute/cdscompute/services.py", line 59, in __call__
    return self.proc(context, *args, **kwargs)
  File "/home/cds/cdsservices/services/python_service.py", line 38, in execute
    raise exceptions.InternalError(logging + traceback, '')
cdsclient.exceptions.InternalError: Traceback (most recent call last):
  File "/opt/cdstoolbox/jsonrequest/jsonrequest/requests.py", line 71, in jsonrequestcall
    resp = coding.encode(req.callable(*req.args, **req.kwargs), register=encoders, **context)
  File "/opt/cdstoolbox/cdscdo/cdscdo/cdo.py", line 274, in _make_regular
    _fwrite_regular(data, xc, yc, regular_path)
  File "/opt/cdstoolbox/cdscdo/cdscdo/cdo.py", line 332, in _fwrite_regular
    xsize = data[x].size
TypeError: list indices must be integers or slices, not str

Hi Catalina

The primary reason you are getting that error is that you are getting an empty data array back from the CDS. In case of the EFAS datasets, you need to add a keyword "format":"netcdf" to your retrieve statement in the Toolbox. I've come across this issue before, which is why I knew there was a solution!

If you include the keyword, you will actually get some data back (you can check this by adding a print statement) with the following coordinates:

Coordinates:
  * y                        (y) float32 752500.0 757500.0 ... 5497500.0
  * x                        (x) float32 2502500.0 2507500.0 ... 7497500.0
  * forecast_reference_time  (forecast_reference_time) datetime64[ns] 2021-03...
  * leadtime                 (leadtime) timedelta64[ns] 0 days 06:00:00 ... 3...
    surface                  int64 ...
    time                     (forecast_reference_time, leadtime) datetime64[ns] ...
    lat                      (y, x) float64 ...
    lon                      (y, x) float64 ...

Unfortunately, the script will then fail in the second step (make_regular) with a different error: 

ValueError: Unsupported: dataset with more than one variable.

As far as I can see, there's only one variable in the array, so I'm not sure why this error comes up. Maybe someone from the Toolbox team can shed some light here?

All the best

Rutger

Hi Rutger,

Thank you for help, I added the format and I got the error you mentioned. 

I hope to find some solution.

All the best,

Catalina