Climate data download from the COPERNICUS Climate data store and CDS toolbox

The atmospheric variables from regional climate models or observations are typically provided in spatial and temporal resolutions that are different from the requirements of the Virtual Ecosystem. This document describes how to download climate data from the Copernicus Climate Data Store (CDS) and basic pre-processing options using the CDS toolbox. You need to create a user account to access all data and functionalities.

Note

At present, the pre-processing does not include scaling or topographic adjustment.

Climate input variables

The abiotic module of the Virtual Ecosystem requires the following climate input variables (or derivatives) at each time step (default: monthly means):

  • Air temperature (typically 2m; mean, minimum, and maximum)

  • Air humidity (typically 2m; relative or specific humidity)

  • Air pressure (typically mean sea level or surface pressure)

  • Wind speed (typically 10m)

  • Precipitation

and optionally:

  • atmospheric \(\ce{CO_{2}}\) concentration

  • soil temperature

  • soil moisture

Step-by-step example

Follow one of the links above to access overview information about the data set. You find a detailed documentation of the data set in the ‘Documentation’ section. To select data, navigate to the tab ‘Download Data’.

Selection

This is an example of a selection of tabs to download historical ‘2m air temperature’ from the CORDEX-SEA (you can download multiple variables and years in one request):

  • Domain (South-East Asia),

  • Experiment (here: ‘historical’, RCPs available)

  • Horizontal resolution (‘0.22 degree x 0.22 degree’)

  • Temporal resolution (‘daily mean’)

  • Variables (here: ‘2m_air_temperature’)

  • Global climate model (here: ‘mohc_hadgem2_es’)

  • Regional climate model (here: ‘gerics_remo2015’)

  • Ensemble member (r1i1p1)

  • Start year and End year (here: 2001-2005)

Once you selected the data, you can either download the dataset for further processing or click on ‘show Toolbox request’ at the bottom of the page, copy the code, and open the CDS toolbox editor.

The code to manipulate climate data as used in the ve_run example is available here.

Toolbox template CORDEX-SEA

The template below describes how to request a data set, reproject the data on a regular grid (note that the projection name is not changed!), select the area of interest, calculate the monthly means, and download the product. For illustration, the routine also plots the mean value. Adjust the ‘data’ lines to match your data request. You find the full documentation of the CDS toolbox here.

# EXAMPLE CODE to preprocess CORDEX-SEA with CDS toolbox

import cdstoolbox as ct

@ct.application(title='Download data')
@ct.output.download()
@ct.output.figure()
def download_application():
    data =ct.catalogue.retrieve(
        'projections-cordex-domains-single-levels',
        {
            'domain': 'south_east_asia',
            'experiment': 'historical',
            'horizontal_resolution': '0_22_degree_x_0_22_degree',
            'temporal_resolution': 'daily_mean',
            'variable': '2m_air_temperature',
            'gcm_model': 'mohc_hadgem2_es',
            'rcm_model': 'gerics_remo2015',
            'ensemble_member': 'r1i1p1',
            'start_year': '2001',
            'end_year': '2005',
        }
    )

    regular = ct.geo.make_regular(data, xref='rlon', yref='rlat')
    sel_extent = ct.cube.select(regular, extent=[116., 118, 4., 6.])
    monthly_mean = ct.climate.monthly_mean(sel_extent)
    
    average = ct.cube.average(monthly_mean, dim='time')
    fig = ct.cdsplot.geomap(average)

    return monthly_mean, fig

The data handling for simulations is managed by the data module and the Data class, which provides the data loading and storage functions for the Virtual Ecosystem. The data system is extendable to provide support for different file formats and axis validation but that is beyond the scope of this document.