Table of Contents
This page is under construction!
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Best practise to iterate over all hindcastDates of several hindcastYears for CMA
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A good understanding of the MARS efficiency issues is essential especially for users that are interested in downloading large amounts of data. The aim of this page is to help users to improve their MARS requests performance focusing in CMA reforecast MARS requests. |
How the S2S data is organised in general?
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First you need to understand how the S2S data is organised in MARS.
In general it is organised, as a huge tree, with the indentation below, 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)
- Hdates (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
- Hdates (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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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)):
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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 Hdates for a CMA request?
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for Hdate in Hdate-list |
An example to request Control forecast, pressure levels from 2010-03-01 to 2010-03-31
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for each Hdate from 2010-03-01 to 2010-03-31 |
An example of "your-API-S2S-request"
Retrieving 1 field (10m U wind) for all time steps
What is the best approach to get all Hdays for several Hyears ?
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The best approach is to iterate over the Hyears you wish. For each Hyear iterate over all Hmonths and for each Hmonth iterate over all its Hdays. |
What is the best approach to get all Hdays for several Hyears and Hmonths and for several hindcasts ?
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for Hyear in Hyears in list(range(numberOfDays)): hindcastDate = '%04d%02d%02d' % ( hindcastYear, hindcastMonth, hindcastDay + 1) Hdatetarget = Hyear-Hmonth-Hday"%s%s.grb" % (origin, hindcastDate) your-S2S-cma_reforecast_request(Hdate) |
An example to request Control forecast, sfc, for Hyears 2010-2014 for 2 Hmonths (eg April and June)
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for each Hyear from 2010 to 2014 for Hmonth in April, June for Hday in Hmonth Hdate = Hyear-Hmonth-Hday hindcastDate, target) def cma_reforecast_request(hindcastDate, target): """ A CMA reforecast request. Change the keywords below to adapt it to your needs. """ server.retrieve({ your-S2S-request(Hdate) |
old below:
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title | The objective: |
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An example to request Control forecast, pressure levels, for Hyears 2010-2014 for 2 Hmonths (eg April and June)
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for each Hyear from 2010 to 2014 for Hmonths April, June |
Useful links
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