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***************  This page is under construction!    *****************


 

What is the objective of this page?

 

title
Info
The objective:

To help users to improve S2S BoM CMA MARS requests performance via the WebAPI.

(lightbulb) A good understanding of the MARS efficiency issues is essential especially for users that are interested in downloading large amounts of data.

 

How is the S2S reforecast data

...

organised in MARS?

 

Info

In general it is organised, as a huge tree, with the indentation below, showing different levels down that tree:

  • centre (BoMCMA, 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
            HindcastDates (2013
            • -01-01 or
            2013
            • 2014-01-02 or
            2013
            • 2014-01-03, ...)
              •  time-steps
                • members (for perturbed forecast)
                  • levels (for pl or pt)
                    • parameters

 

What would be the natural way to group requests?

 

Info

(lightbulb) The idea is to request as much data as possible from the same tape file, all time-steps, all members, all parameters for a type of level, a type, a HindcastDate

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. The natural way to group requests

...

Info

Following the previous paragraph,  the natural way to group requests would be:
all parameters, all levels, all members, all time-steps for 1 HindcastDate.hindcast date for a type of level for a type

(warning) 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 HindcastDates hindcast dates in one go, since the overall request will not be so big.

What is the best approach to loop over several HindcastDates  for a BoM request?

...

titleThe main idea in brief:

 

Best practise to iterate over all hindcastDates of several hindcastYears for CMA

 

Info

(lightbulb)

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What is the best approach to get all HindcastDays for several HindcastYears ?

The best approach is to iterate over the

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hindcastYears. For each

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hindcastYear iterate over all

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the available hindcastMonths and for each

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hindcastMonth iterate over all

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the available hindcastDays.

(warning) At this point you may wish to check CMA availability and to view a CMA request

 

 

 

Info
for hindcastYear in hindcastYears
Info
titleThe main idea in brief:
for HindcastYear in HindcastYears
    for HindcastMonthhindcastMonth in HindcastYearhindcastMonths        
        for HindcastDayhindcastDay in HindcastMonthhindcastDays             
            HindcastDatehindcastDate = HindcastYear-HindcastMonthhindcastMonth-HindcastDayshindcastDay               
                S2S-request(HindcastDate)

An example to request Perturbed forecast, pl, for HindcastYears 2012 to 2013 for 2 HindcastMonths  (eg August & September)

Info
titleThe main idea in brief:
for HindcastYear from 2012 to 2013   
    for HindcastMonth in 08, 09        
        for HindcastDay in HindcastMonth             
            HindcastDate = HindcastYear-HindcastMonth-HindcastDay             
                S2S-request(HindcastDate) (see below an example)

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hindcastDate)

 

Web-API examples:

 

A CMA reforecast request for one hindcastDate

 

Info

The request below is for all members of the perturbed forecast, 10 meter U and V wind components, for all time-steps and for model version 2014-05-01

 

 

 

Code Block
languagepy
#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
modelVersionDate = "2014-05-01"  # This is the first model version for CMA (babj)
hindcastDate = "2014-04-01"      # The selected hindcast date
server = ECMWFDataServer()
server.retrieve({
    "class": "s2",
    "dataset": "s2s",
    "date": modelVersionDate,
    "expver": "prod",
    "hdate": hindcastDate, 
    "levtype": "sfc",
    "origin": "babj",
    "param": "165/166",
    "step": "24/to/1440/by/24",
    "stream": "enfh",
    "target": "data.pf.sfc",
    "time": "00",
    "number": "1/2/3",
    "type": "pf",
})

 

A CMA reforecast request for several hindcastDates

 

Info
  • The objective of this example is to demonstrate how to make a request efficient by iterating properly over several hindcastYears, hindcastMonths and hindcastDays
  • It can be used as a starting point however you need to adapt it to your needseg to set the keyword values (eg hindcastYear).
  • In this way you can extend this request to download the whole S2S CMA reforecast,  but don't forget to check CMA availability (warning)

(warning) Please note: use the variable "target"  to write each hindcastDate on a separate file .

 

v1.0

 

Code Block
languagepy
#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()

origin = "babj"
modelVersionDate = "2014-05-01"

def retrieve_data(hindcastDate,modelVersionDate,centre):
    target = "target_s2s_%s_%s.grb" % centre % hindcastDate
    server.retrieve({
       "class": "s2",
       "dataset": "s2s",
       "date": "2014-01-01"modelVersionDate,
       "expver": "prod",
       "hdate": HindcastDate, (ie the selected HindcastDate eg "2013-09-01") hindcastDate,
       "levtype": "sfc",
       "origin": centre,
       "levelistparam":"10/50/100/200 "165",
    
    "levtypestep": "pl0",
       "originstream": "ammc",
"enfh",
       "target": target,
       "paramtime": "133/15600",
       "steptype": "24/48
    "number": "1/2/3/4/5/",
    "stream": "enfh",
    "target": "CHANGEME",
    "time": "00",
    "type": "pf",
})

(lightbulb) If the request is "small" you may request more HindcastDates in one go.

(smile) You can also  check the S2S BoM reforecast availability  or view more BoM re-forecast examples ?

"cf",
})

hindcastYearList = ["2012", "2013"]
hindcastMonthList = ["08", "09"]
hindcastDayList = ["01", "02"]

for hindcastYear in hindcastYearList:
   for hindcastMonth in hindcastMonthList:
       for hindcastDay in hindcastDayList:
           hindcastDate = hindcastYear + hindcastMonth + hindcastDay
               retrieve_data(hindcastDate)

 

 

 

Code Block
languagepy
titleCMA
for hindcastYear in ["2012", "2013"]:
    for hindcastMonth in ["08", "09"]:
         if hindcastMonth in ["01", "03", "05", "07", "08", "10", "12"]: hindcastDateEnd = "31"
         if hindcastMonth in [ "04", "06", "09", "11"]: hindcastDateEnd = "30"
         for hindcastDay in ["01" ... hindcastDateEnd ]:
            hindcastDate = hindcastYear+hindcastMonth+hindcastDay
            retrieve_data(hindcastDate,"2014-05-01","babj")

 

BoM example

 

Code Block
languagepy
titleBoM
for hindcastYear in ["2012", "2013"]:
    for hindcastMonth in ["08", "09"]:
         for hindcastDay in ["01"  "06" "11" "16" "21" "26"]:
            hindcastDate = hindcastYear+hindcastMonth+hindcastDay
            retrieve_data(hindcastDate,"2014-01-01","ammc")

 

Useful links

 

Info

 

 

 

 

 


 










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