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The objective of this example is to demonstrate how to iterate efficiently over all the available hindcastYears, hindcastMonths and hindcastDays for an ECMWF model version date.
You firstly need to know the model version date and the correct Hindcast Days you wish to requestretrieve. For more information you may wish to visit A brief description of reforecasts. Keep in mind that the ECMWF reforecast configuration is "on the fly"
It can be used as a starting point, however you need to keep in mind that you have to adapt it to your needseg to set the keyword values according to your requirements ("param", "levtype", "step" etc).
In this way you can extend this request to download the whole S2S ECMW Freforecast. Don't forget to check ECMWF availability

Please note:

the most efficient way is to request all hindcastDates of a hindcastMonth, in one request, like the example below.

you
You can use the variable target to write the requested data as you wish. In the example below the data is written per leveltype (sfc, pl) per hindcastMonth.

Code Block

language	py

#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()

origin = "ecmf"
modelVersionDate = "2015-12-03"
hindcastDates = ["1995-12-03", "1996-12-03", "1997-12-03", "1998-12-03", "1999-12-03", "2000-12-03",
    "2001-12-03", "2002-12-03", "2003-12-03", "2004-12-03", "2005-12-03", "2006-12-03", "2007-12-03", 
    "2008-12-03", "2009-12-03", "2010-12-03", "2011-12-03", "2012-12-03", "2013-12-03", "2014-12-03"]

def retrieve_ECMWF_reforecast():
    """
       A function to demonstrate how to iterate efficiently over all hindcastDays 
       for a particular ECMWF reforecast model version.
       Change the variables below to adapt the iteration to your needs
    """
           
    #Please note: the steps 4 and 5 below could run in parallel
           
    #Step 4: Get all the available perturbed forecast, pressure level data
    pfplTarget = "%s_%s_%_%s.grb" % (origin, "pfpl", modelVersionDate)
    ECMWF_reforecast_pf_pl_request("/".join(hindcastDates), pfplTarget)
           
    #Step 5: Get all the available perturbed forecast, surface data
    pfsfcTarget = "%s_%s_%_%s.grb" % (origin, "pfsfc", modelVersionDate)
    ECMWF_reforecast_pf_sfc_request("/".join(hindcastDates), pfsfcTarget)

def ECMWF_reforecast_pf_pl_request(hindcastDate, target):
    """
       A ECMWF reforecast, perturbed forecast, pressure level, request.
       The cost of this request is fields and  Gbytes 
       Change the keywords below to adapt it to your needs.
    """
    server.retrieve({
        "class": "s2",
        "dataset": "s2s",
        "date": modelVersionDate,
        "expver": "prod",
        "hdate": hindcastDates,
        "levtype": "pl",
        "levelist": "10/50/100/200/300/500/700/850/925/1000",
        "origin": origin,
        "param": "130/131/132/133/135/156",
        "step": "24/to/768/by/24",
        "stream": "enfh",
        "target": target,
        "time": "00",
        "number": "1/2/3/4",
        "type": "pf",
    })

def ECMWF_reforecast_pf_sfc_request(hindcastDate, target):
    """
       A ECMWFreforecast, perturbed forecast, sfc request.
       The cost of this request is 383,040 fields and 7.1 GB
       Change the keywords below to adapt it to your needs.
    """
    server.retrieve({
        "class": "s2",
        "dataset": "s2s",
        "date": modelVersionDate,
        "expver": "prod",
        "hdate": hindcastDate,
        "levtype": "sfc",
        "origin": origin,
        "param": "1/33/34/59/121/122/134/136/146/147/151/165/166/167/168/169/175/176/177/179/180/181/235",
        "step": "24/to/744/by/24",
        "stream": "enfh",
        "target": target,
        "time": "00",
        "number": "1/2/3/4",
        "type": "pf",
    })

if __name__ == '__main__':
    retrieve_ECMWF_reforecast()

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