ERA5PrecipitationtoDelft3D

"""
Created on Wed Jun 19 2024

@author: Faezah Maghsoodifar

This script reads precipitation data from a netCDF file generated by the ERA5 dataset.
It processes the data by flipping the precipitation values along the latitude axis
and adjusting longitude values to fit within the [-180, 180] range. The script saves
the processed data into a new netCDF file in the NETCDF4 format. The time units are
preserved to ensure correct dates.
"""

import os
import numpy as np
from netCDF4 import Dataset

def process_netcdf(input_filepath, output_filepath):
    """
    Process the input netCDF file and write the required data to a new netCDF file.

    Parameters:
    input_filepath (str): Path to the input netCDF file.
    output_filepath (str): Path to save the output netCDF file.
    """
    try:
        # Open the input netCDF file in read mode
        with Dataset(input_filepath, 'r') as ncid0:
            # Read longitude values from the netCDF file
            lon = ncid0.variables['longitude'][:]
            lon[lon >= 180] = lon[lon >= 180] - 360  # Adjust longitudes to [-180, 180] range
            lon = np.sort(lon)  # Sort longitudes

            # Read latitude values
            lat = ncid0.variables['latitude'][:]

            # Read time values and their original units
            time = ncid0.variables['valid_time'][:]
            time_units = ncid0.variables['valid_time'].units  # Fetch original units

            # Read total precipitation values and flip along the latitude axis
            Tprec = ncid0.variables['tp'][:, :, :]
            Tprec_flipped = np.flip(Tprec, axis=1)

            # Create the output netCDF file in write mode
            with Dataset(output_filepath, 'w', format='NETCDF4') as ncid:
                # Define dimensions
                ncid.createDimension('valid_time', len(time))
                ncid.createDimension('y', len(lat))
                ncid.createDimension('x', len(lon))

                # Define and write longitude variable
                var_lon = ncid.createVariable('X', 'f8', ('x',))
                var_lon.units = 'degrees_east'
                var_lon.standard_name = 'longitude'
                var_lon[:] = lon

                # Define and write latitude variable
                var_lat = ncid.createVariable('Y', 'f8', ('y',))
                var_lat.units = 'degrees_north'
                var_lat.standard_name = 'latitude'
                var_lat[:] = lat

                # Define and write time variable
                var_time = ncid.createVariable('time', 'f8', ('valid_time',))
                var_time.units = time_units  # Preserve original time units
                var_time.calendar = 'gregorian'
                var_time.standard_name = 'time'
                var_time.long_name = 'Time'
                var_time[:] = time

                # Define and write total precipitation (rainfall)
                var_tprec = ncid.createVariable('rainfall', 'f4', ('valid_time', 'y', 'x'))
                var_tprec.units = 'm'
                var_tprec.long_name = 'rainfall'
                var_tprec.standard_name = 'rainfall'
                var_tprec[:, :, :] = Tprec_flipped

                print("NetCDF file successfully created:", output_filepath)

    except Exception as e:
        print(f"An error occurred: {e}")


def main():
    """
    Main function to set paths and process the netCDF file.
    """
    # USER-DEFINED INPUT: Set input/output paths
    dinput = input("Enter the input directory path: ").strip()  # Input directory
    doutput = input("Enter the output directory path: ").strip()  # Output directory

    filename = 'data_stream-oper.nc'  # Input file name
    input_filepath = os.path.join(dinput, filename)
    output_filepath = os.path.join(doutput, filename.replace('.nc', '_dfm.nc'))

    # Process the netCDF file
    process_netcdf(input_filepath, output_filepath)


if __name__ == "__main__":
    main()