netsse.model.era5.retrieve_dirwavespec

netsse.model.era5.retrieve_dirwavespec(index_month=0, folder_output='../Output/')

Retrieve directional wave spectrum data from the ERA5 dataset (Hersbach et al., 2020, 2023).

The function retrieves data from the ERA5 dataset for a specific period of time and geographical area. The latter must be specified in a dedicated ‘ERA5_request.csv’ file at the location path given in folder_output informing the spatial and temporal coverage of the data to be retrieved. The content of the file must follow the example below (including the header line!):

,Year,Month,Day_start,Day_end,NrDays,Longitude_min,Longitude_max,Latitude_min,Latitude_max
0,2007,9,12,25,30,-55.0,-5.0,46.0,50.0
1,2007,10,12,26,31,-55.0,-5.0,45.0,50.0

There can be as many lines as needed in the ERA5 request file, each line corresponding to a single retrieval request of data located all within the same month. The function retrieves the directional wave spectrum data for the request line having the index index_month in the file. The default value for index_month is 0, which means to submit the first request in the request file.

The data is retrieved for the month and year specified in the ‘Month’ and ‘Year’ columns of the request file; e.g., September 2007 in the first request contained in the above example). The retrieval period covers from the start day at 00:00 to the end day at 23:00; e.g., from 12 September 2007 at 00:00 to 25 September 2007 at 23:00 in the first request contained in the above example.

Longitudes are specified in degrees East and latitudes in degrees North. The data is retrieved for the geographical area defined by the minimum and maximum longitudes and latitudes; e.g., from 46.0 to 50.0 degrees North and from -55.0 to -5.0 degrees East in the first request contained in the above example. The spatial resolution is fixed to 0.5 degrees in both latitude and longitude.

The data is retrieved using the Copernicus Climate Data Store (CDS) API. The user must have a valid CDS API key to access the data. The downloaded data is stored in a NetCDF file at the location path specified in the variable folder_output. The default value for folder_output is '../Output/'.

References

1. Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R., Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L., Healy, S., Hogan, R. J., Hólm, E., Janisková, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum, I., Vamborg, F., Villaume, S., and Thépaut, J. N. The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society 146, 730 (2020), 1999–2049, DOI: 10.1002/qj.3803.

2. Hersbach, H., Bell, B., Berrisford, P., Biavati, G., Horányi, A., Muñoz Sabater, J., Nicolas, J., Peubey, C., Radu, R., Rozum, I., Schepers, D., Simmons, A., Soci, C., Dee, D., Thépaut, J-N. (2023): ERA5 hourly data on single levels from 1940 to present. Copernicus Climate Change Service (C3S) Climate Data Store (CDS), DOI: 10.24381/cds.adbb2d47 (Accessed on 26-02-2025).

Example

To retrieve the directional wave spectrum data for the month with index 1 in the file ‘ERA5_request.csv’ stored in the folder ‘../Output/’, run:

>>> retrieve_dirwavespec(index_month=1,folder_output='../Output/')
>>> # Output:
>>> # Retrieving ERA5 data for the month with index 1...
>>> # Selected dates: 2007-10-12/to/2007-10-26
>>> # Selected area: 50.0/-55.0/45.0/-5.0
>>> # The downloaded file is stored at '../Output/ERA5_2D_spectra_2007-10.nc'.