Best practise to iterate over all hindcastDates of several hindcastYears for CMA
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for hindcastYear in hindcastYears |
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 ?
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.
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for HindcastYear in HindcastYears |
An example to request Control forecast, sfc, for HindcastYears 2010 to 2014 for 2 HindcastMonths (eg April and June)
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for HindcastYear from 2010 to 2014 |
A simple web API example, requesting Control forecast, sfc for one hdate
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#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
"class": "s2",
"dataset": "s2s",
"date": ModelVersionDate, (ie "2014-05-01"),
"expver": "prod",
"hdate": HindcastDate, (ie the selected HindcastDate eg "2014-04-01"),
"levtype": "sfc",
"origin": "babj",
"param": "165",
"step": "0",
"stream": "enfh",
"target": "CHANGEME",
"time": "00",
"type": "cf",
}) |
If the request is "small" you may request more HindcastDates in one go.
Do you need more CMA re-forecast examples?
A web API example requesting data for several hindcastDates (iterating over several hindcastYears, hindcastMonths and hindcastDays)
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- to set the keywords values (eg hindcastYear) according to your needs.
Don't forget to check the availability!
- to make it more "pythonic"
- etc
hindcastDate) |
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)
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.
"""
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#!/usr/bin/env python from ecmwfapi import ECMWFDataServer server = ECMWFDataServer() def retrieve_data(hindcastDate): target = "target_s2s_%s.grb" % hindcastDate 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": "cf1/2/3", }) for hindcastYear in ["2012", "2013"]: for hindcastMonth in ["08", "09"]: for hindcastDay in ["01", "02"]:type": "pf", }) if hindcastDate = hindcastYear+hindcastMonth+hindcastDay__name__ == '__main__': retrieve_data(hindcastDate)retrieve_cma_reforecast() |
Useful links
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