Source code for IRData.cera20c.fetch

# (C) British Crown Copyright 2017, Met Office
#
# This code is free software: you can redistribute it and/or modify it under
# the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This code is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#

# Functions to fetch CERA data through the ECMWF Public data API

import os
import subprocess
import calendar
import ecmwfapi
import datetime

from .utils import _hourly_get_file_name
from .utils import _translate_for_file_names
from .utils import monolevel_analysis
from .utils import monolevel_forecast

def fetch(variable,dtime):
    """Get all data for one variable, for one month, from ECMWF's archive.

    Data wil be stored locally in directory $SCRATCH/CERA-20C, to be retrieved by :func:`load`. If the local file that would be produced already exists, this function does nothing.

    Args:
        variable (:obj:`str`): Variable to fetch (e.g. 'prmsl')
        dtime (:obj:`datetime.datetime`): Date-time to fetch the data for.
        month (:obj:`int`): Month to get data for (1-12).

    Will retrieve the data for the year and month of the given date-time. If the selected time is within 6-hours of the end of the calendar month, loading data for that time will also need data from the next calendar month (for interpolation). In this case, also fetch the data for the next calendar month. 

    Raises:
        StandardError: If Variable is not a supported value.

    |
    """

    ndtime=dtime+datetime.timedelta(hours=6)
    if ndtime.month!=dtime.month:
        fetch(variable,ndtime)
    if variable in monolevel_analysis:
        return _fetch_analysis_data_for_month(variable,
                                      dtime.year,dtime.month)
    if variable in monolevel_forecast:
        return  _fetch_forecast_data_for_month(variable,
                                      dtime.year,dtime.month)
    raise Exception("Unsupported variable %s" % variable)

def _fetch_analysis_data_for_month(variable,year,month):
        
    local_file=_hourly_get_file_name(variable,year,month)
    if os.path.isfile(local_file):
        # Got this data already
        return

    if not os.path.exists(os.path.dirname(local_file)):
        os.makedirs(os.path.dirname(local_file))

    server = ecmwfapi.ECMWFDataServer()
    server.retrieve({
        'dataset'   : 'cera20c',
        'stream'    : 'enda',
        'type'      : 'an',
        'class'     : 'ep',
        'expver'    : '1',
        'levtype'   : 'sfc',
        'param'     : _translate_for_file_names(variable),
        'time'      : '00/03/06/09/12/15/18/21',
        'grid'      : '1.25/1.25',
        'number'    : '0/1/2/3/4/5/6/7/8/9',
        'date'      : "%04d-%02d-%02d/to/%04d-%02d-%02d" %
                       (year,month,1,
                        year,month,
                        calendar.monthrange(year,month)[1]),
        'format'    : 'netcdf',
        'target'    : local_file
    })

def _fetch_forecast_data_for_month(variable,year,month):
        
    # Want 27 hours of forecast for each day
    #         (so we can interpolate over the seam),
    #  but the 27-hr forcast from one day has the same
    #      validity time as the 3-hr forecast from the
    #       next day - so need to download them separately
    #       and store in different files.

    # First 24-hours of forecast in main file
    local_file=_hourly_get_file_name(variable,year,month,
                                    fc_init=None)
    if os.path.isfile(local_file):
        # Got this data already
        return

    if not os.path.exists(os.path.dirname(local_file)):
        os.makedirs(os.path.dirname(local_file))

    server = ecmwfapi.ECMWFDataServer()
    server.retrieve({
        'dataset'   : 'cera20c',
        'stream'    : 'enda',
        'type'      : 'fc',
        'class'     : 'ep',
        'expver'    : '1',
        'levtype'   : 'sfc',
        'param'     : _translate_for_file_names(variable),
        'time'      : '18',
        'step'      : '3/6/9/12/15/18/21/24',
        'grid'      : '1.25/1.25',
        'number'    : '0/1/2/3/4/5/6/7/8/9',
        'date'      : "%04d-%02d-%02d/to/%04d-%02d-%02d" %
                       (year,month,1,
                        year,month,
                        calendar.monthrange(year,month)[1]),
        'format'    : 'netcdf',
        'target'    : local_file
    })


    # 27-hour forecast in additional file
    local_file=_hourly_get_file_name(variable,year,month,
                                     fc_init='last')
    if os.path.isfile(local_file):
        # Got this data already
        return

    if not os.path.exists(os.path.dirname(local_file)):
        os.makedirs(os.path.dirname(local_file))

    server = ecmwfapi.ECMWFDataServer()
    server.retrieve({
        'dataset'   : 'cera20c',
        'stream'    : 'enda',
        'type'      : 'fc',
        'class'     : 'ep',
        'expver'    : '1',
        'levtype'   : 'sfc',
        'param'     : _translate_for_file_names(variable),
        'time'      : '18',
        'step'      : '27',
        'grid'      : '1.25/1.25',
        'number'    : '0/1/2/3/4/5/6/7/8/9',
        'date'      : "%04d-%02d-%02d/to/%04d-%02d-%02d" %
                       (year,month,1,
                        year,month,
                        calendar.monthrange(year,month)[1]),
        'format'    : 'netcdf',
        'target'    : local_file
    })