An ECMWF reforecast request for all the available hindcastDates of an ECMWF model version date
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Table of Contents
What is the objective of this page?
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To help users to improve S2S ECMWF MARS requests performance via the WebAPI. A good understanding of the MARS efficiency issues is essential especially for users that are interested in downloading large amounts of data. |
How is the S2S reforecast data organised in MARS?
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In general it is organised, as a huge tree, with the indentation below, showing different levels down that tree:
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What would be the natural way to group requests?
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The idea is to request as much data as possible from the same tape file. The natural way to group requests would be: Note the following:
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Web-API examples:
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To start writing your request you firstly need to know the model version date and the corresponding Hindcast Days you wish to retrieve.
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An ECMWF reforecast request for all the available hindcastDates
You can use the variable target to write organise the requested data in files as you wish. In the example below the data is written per leveltype (sfc, pl) per hindcastMonth. |
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#!/usr/bin/env python from ecmwfapi import ECMWFDataServer server = ECMWFDataServer() origin = "ecmf" # Step 1: Select a Model Version Date modelVersionDate = "2015-12-03" # Step 2: Set the hindcast Dates you wish to request # For the model version "2015-12-03" the available hindcast dates are listed below: 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 iterateretrieve efficiently over all hindcastDates for a particular ECMWF reforecast model version. Change the variables below to adapt the iterationrequest to your needs """ #Please# Please note that the "sfc" and "pl" requests below could run in parallel #Step # Step 1: Get pressure level data pfplTarget = "%s_%s_%s.grb" % (origin, "pfpl", modelVersionDate) ECMWF_reforecast_pf_pl_request("/".join(hindcastDates), pfplTarget) # #Step Step 2: Get 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): """ AAn 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. (eg to add or remove some steps or parameters etc) """ 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): """ An A ECMWFreforecast, perturbed forecast, sfc request. TheChange costthe ofkeywords thisbelow requestto isadapt 383,040it fieldsto andyour 7needs.1 GB (eg to add or remove some steps Changeor the keywords below to adapt it to your needs.parameters etc) """ 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() |
Useful links
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