Best practise to iterate over all hindcastDates of several hindcastYears for CMA
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for hindcastYear in hindcastYears |
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"
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)
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Table of Contents
This page is under construction!
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In this area we are only focusing on MARS efficiency issues ie to investigate and present what is the most efficient way to loop over several requests for retrieving CMA reforecast data. |
How the S2S data is organised in general:
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The data is organised as a huge tree, with the indentation showing different levels down that tree:
- centre (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)
- dates (2015-01-01 or 2015-01-05 or 2015-01-08, ...)
- time-steps
- members (for perturbed forecast)
- levels (for pl or pt)
- parameters
- levels (for pl or pt)
- members (for perturbed forecast)
- time-steps
- dates (2015-01-01 or 2015-01-05 or 2015-01-08, ...)
- 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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It
doesn't have to be all parameters. If you are interested only on z500, you
may be able to request more dates in one go, since the overall request will
not be so big. We have documented some sample retrievals here:
What would be the natural way to group requests:
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The natural way to group requests would be: Note the following:
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What is the most efficient way to loop over several CMA requests?
If you need to loop in a API requests, follow the hierarchy below
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date (year loop) date (month loop) hindcast date number (EPS only) level parameter (inner loop) |
An example on how to request Control forecast, pressure levels, for years 2010-2014 for month April and June
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for each year from 2010 to 2014 for months April, June | ||
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for each year from 2010 to 2014 for monthsA April,CMA June |
old below:
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title | The objective: |
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"date": modelVersionDate,
"expver": "prod",
"hdate": hindcastDate,
"levtype": "sfc",
"origin": origin,
"param": "165/166",
"step": "24/to/1440/by/24",
"stream": "enfh",
"target": target,
"time": "00",
"number": "1/2/3",
"type": "pf",
})
if __name__ == '__main__':
retrieve_cma_reforecast() |
Useful links
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