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Table of Contents

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The objective:

Info
titleThe objective:

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.

...

Info

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
(


with aiming to be in the same tape file, all time-steps, all members, all parameters for a type of level, a type, a date

)
So that would be the natural way to group requests:
all parameters, all levels, all members, all time-steps for 1 date.
Note that when I refer to 'all', I mean 'all' that the user wants.

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:

Info

The natural way to group requests would be:
all parameters, all levels, all members, all time-steps for 1 date.

Note the following:

  1. 'all' means 'all' that the user wants. It doesn't have to be all parameters.
  2. If a user is interested only on z500,  he may request more dates in one go, since the overall request will not be so big.

 

 

 

 

 

 

What is the most efficient way to loop over several CMA requests?

...

Info
titleThe main idea in brief:

Taking under consideration what has been presented above if you need to loop in a

...

MARS request, follow the hierarchy below

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The main idea in brief:
Info
title

  • date (year
loop)   date (
  • and month loop)
     
    • hindcast date
              
          • number (EPS only)
                     
                • level
                            
                      • parameter (inner loop)

        ...

        A more practical example on how to request Control forecast, pressure levels, for years 2010-2014 for month April and June

        Info
        titleThe main idea in brief:
        for each year from 2010 to 2014
            for months April, June
                for each hindcast date
                    API request

        ...