Best practise to iterate over all hindcastDates of several hindcastYears for CMA
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- The best approach is to iterate over the hindcastYears.
- For each hindcastYear iterate over all the available hindcastMonths and for each hindcastMonth iterate over all the available hindcastDays.
 At this point you may wish to check CMA availability and to view a CMA request
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for hindcastYear in hindcastYears
for hindcastMonth in hindcastMonths
for hindcastDay in hindcastDays
hindcastDate = hindcastYear-hindcastMonth-hindcastDay
S2S-request(hindcastDate) |
Web-API examples:
A CMA reforecast request for all the available hindcastDates
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- The objective of this example is to demonstrate how to iterate efficiently over all the available hindcastYears, hindcastMonths and hindcastDays for a CMA reforecast request
- It can be used as a starting point, however you need to keep in mind that you have to adapt it to your needseg to set the keyword values according to your requirements ("param", "levtype", "step" etc).
- In this way you can extend this request to download the whole S2S CMA reforecast.
Please note: - you can set the variable "target" to write each hindcastDate on a separate file
- taking under consideration your request's size (eg Nr of fields and volume) you can merge several hindcastDates on the same "target"
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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)
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This page is under construction!
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To help users to improve S2S CMA MARS requests performance. A good understanding of the MARS efficiency issues is essential especially for users that are interested in downloading large amounts of data. |
How the S2S data is organised in general?
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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)
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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:
all parameters, all levels, all members, all time-steps for 1 Hdate.  Note the following:
- 'all' means 'all' that the user wants. It doesn't have to be all parameters.
- If a user is interested only on z500, he may request more Hdates in one go, since the overall request will not be so big.
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What is the best approach to loop over several Hdates for a CMA request?
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| title | The main idea in brief: |
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for Hdate in Hdate-list
s2S-request(Hdate) |
An example to request Control forecast, pressure levels from 2010-03-01 to 2010-03-31
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| title | The main idea in brief: |
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for each Hdate from 2010-03-01 to 2010-03-31
s2S-request(Hdate) |
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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| title | The main idea in brief: |
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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.
for Hyear in Hyears
for Hmonth in Hyear
for Hdays in Hmonth
Hdatetarget = Hyear-Hmonth-Hday "%s%s.grb" % (origin, hindcastDate)
s2S-request(Hdate) |
What is the best approach to get all Hdays for several Hyears and Hmonths and for several hindcasts ?
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| title | The main idea in brief: |
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for Hyear in Hyears
for Hmonth in Hyear
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({
for Hdays in Hmonth"class": "s2",
"dataset": "s2s",
Hdate = Hyear-Hmonth-Hday "date": modelVersionDate,
"expver": "prod",
s2S-request(Hdate) |
An example to request Control forecast, sfc, for Hyears 2010-2014 for 2 Hmonths (eg April and June)
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| title | The main idea in brief: |
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for each Hyear from 2010 to 2014 for Hmonth in April, June "hdate": hindcastDate,
"levtype": "sfc",
"origin": origin,
"param": "165/166",
"step": "24/to/1440/by/24",
"stream": "enfh",
"target": target,
for Hday in Hmonth"time": "00",
"number": "1/2/3",
Hdate = Hyear-Hmonth-Hday "type": "pf",
})
if __name__ == '__main__':
s2S-request(Hdate)retrieve_cma_reforecast() |
Useful links
