Sampled SSH and error fields

At each pass, for each cycle, an output netCDF file containing the SSH interpolated from the model (if ssh_plugin is not set to None), and the different errors. The naming and the file format are compliant with SWOT’s PDD (Product Description Document), set complete_product key to True to store all the variables and False to store only the one compute by the simulator.

You can also select the output type product_type among basic, expert, unsmoothed, and wind_wave. Default is expert and details are in the corresponding XML file.

The output directory is defined in working_directory key, default is the user’s root. The output file names are stored in the output directory in karin/<year> directory for SWOT and nadir/<year> directory for the nadir. The naming follows the pattern :

  • SWOT_L2_LR_Expert_[cycle]_[pass]_[start_time]_[stop_time]_DG10_01.nc for the Karin products and

  • SWOT_GPR_2PTP[cycle]_[pass]_[start_time]_[stop_time].nc for the nadir products.

The interpolation method is specified in your SSH plugin. pangeo-pyinterp module is used in the examples.

The nadir and swath parameters enable (parameter set to True) or disable (parameter set to False) the generation of these products.

Computation of errors are specified as a list:

noise = ['altimeter',
         'baseline_dilation',
         'karin',
         'corrected_roll_phase',
         'timing',
         'wet_troposphere']

Note

corrected_roll_phase error will generate already cross-calibrated roll-phase error whereas roll_phase will generate errors before cross-calibration.

A repeat length len_repeat = 2000 key defines the wavelength in km to repeat the noise and is used for all noises. The path to the file that contains instrumental errors is mentioned in error_spectrum key. It is possible to specify the seed for Randomstate in nseed. The following parameters are specific to each noise component:

  • KaRIN: The file noise that contains the spectrum is available in karin_noise, a constant swh can be set swh=2 or interpolated from a model SWH specified in the plugin swh_plugin.

  • Roll-phase: To use the already cross-calibrated roll phase, download the file from the FTP (https://ftp.odl.bzh/swot) and specify the path in the corrected_roll_phase_dataset key. So far, the following files are available:

    • data_sim_slope_v0.nc: One year of cross-calibrated roll-phase

    • data_sim_slope_2cycles_v0.nc: Two cycles of cross-calibrated roll-phase

  • Wet troposphere: The number of beams used to correct the wet troposphere is set in nbeam variable. The beam position of each beam can be set as a list in beam_position, and the gaussian footprint can be changed using sigma variable.