Best practise to iterate over all hindcastDates of several hindcastYears for CMA
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Table of Contents
What is the objective of this page?
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To help users to improve S2S CMA MARS requests performance via the WebAPI.
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How the S2S data is 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:
- centre (CMA, ECMWF, NCEP, JMA, ...)
- realtime or reforecast
- type of data (control forecast or perturbed forecast)
- type of level (single level or pressure level or potential temperature)
- model version date (2014-05-01 or ...)
- hindcast dates (2014-01-01 or 2014-01-02 or 2014-01-03, ...)
- time-steps
- members (for perturbed forecast)
- levels (for pl or pt)
- parameters
- levels (for pl or pt)
- members (for perturbed forecast)
- time-steps
- hindcast dates (2014-01-01 or 2014-01-02 or 2014-01-03, ...)
- model version date (2014-05-01 or ...)
- type of level (single level or pressure level or potential temperature)
- type of data (control forecast or perturbed forecast)
- realtime or reforecast
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What would be the natural way to group requests?
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Following the previous paragraph, the natural way to group requests would be:
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What is the best approach to loop over several hindcastDates for a CMA request?
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title | The main idea in brief: |
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What is the best approach to get all hindcastDays for several HindcastYears ?
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for hindcastYear in hindcastYears |
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Web-API examples:
A CMA reforecast request for all the available hindcastDates
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Please note:
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#!/usr/bin/env python import calendar from ecmwfapi import ECMWFDataServer server = ECMWFDataServer() origin = "babj" modelVersionDate = "2014-05-01" hindcastDate = "2014-04-01" # The selected hindcast date server = ECMWFDataServer() server.retrieve({ "class": "s2", "dataset": "s2s", "date": modelVersionDate, "expver": "prod", "hdate": hindcastDate, "levtype": "sfc", "origin": "babj", "param": "165", "step": "0", "stream": "enfh", "target": "data.cf.sfc", "time": "00", "type": "cf", }) |
A web API example requesting data for several hindcastDates (iterating over several hindcastYears, hindcastMonths and hindcastDays)
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#!/usr/bin/env python from ecmwfapi import ECMWFDataServer server = ECMWFDataServer() def retrieve_data(hindcastDate): target = "target_s2s_%s.grb" % hindcastDate def retrieve_cma_reforecast(): """ A function to demonstrate how to iterate efficiently over all hindcastYears, hindcastMonths etc for a particular cma_reforecast_request. Change the variables below to adapt the iteration to your needs """ hindcastYearStart = 1994 hindcastYearEnd = 2014 hindcastMonthStart = 1 hindcastMonthEnd = 12 for hindcastYear in list(range(hindcastYearStart, hindcastYearEnd + 1)): for hindcastMonth in list(range(hindcastMonthStart, hindcastMonthEnd + 1)): numberOfDays = calendar.monthrange(hindcastYear, hindcastMonth)[1] for hindcastDay in list(range(numberOfDays)): hindcastDate = '%04d%02d%02d' % ( hindcastYear, hindcastMonth, hindcastDay + 1) target = "%s%s.grb" % (origin, hindcastDate) cma_reforecast_request(hindcastDate, target) def cma_reforecast_request(hindcastDate, target): """ A CMA reforecast request. Change the keywords below to adapt it to your needs. """ server.retrieve({ "class": "s2", "dataset": "s2s", "date": "2014-05-01"modelVersionDate, "expver": "prod", "hdate": hindcastDate, "levtype": "sfc", "origin": "babj"origin, "param": "165/166", "step": "024/to/1440/by/24", "stream": "enfh", "target": target, "time": "00", "typenumber": "cf", }) for hindcastYear in ["2012", "2013"]:1/2/3", for hindcastMonth in ["08", "09type"]: for hindcastDay in ["01", "02"]:"pf", }) if hindcastDate = hindcastYear+hindcastMonth+hindcastDay __name__ == '__main__': retrieve_datacma_reforecast(hindcastDate)) |
Useful links
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