What is the objective of this page?
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To help users to improve S2S BoM MARS requests performance via the WebAPI. A good understanding of the MARS efficiency issues is essential especially for users that are interested in downloading large amounts of data.
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How is the S2S reforecast data 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 (BoM, 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 (2014-01-01 or ...)
- hindcast dates (2013-09-01, 2013-09-06, 2013-09-11, 2013-09-16, 2013-09-21, 2013-09-26, ...)
- time and steps
- members (for perturbed forecast)
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What would be the natural way to group requests?
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The idea is to request as much data as possible from the same tape file. The natural way to group requests would be: all parameters, all levels, all members, all time-steps for 1 hindcast date for a type of level for a type 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 hindcast dates in one go, since the overall request will not be so big.
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Best practise to iterate over all hindcastDates of several hindcastYears for BoM
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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 BoM availability and to view a BoM 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 BoM 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 BoM 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 BoM reforecast. Don't forget to check BoM availability
![(warning)](/s/biakzp/9012/ly29vq/_/images/icons/emoticons/warning.svg)
Please note:
- the most efficient way is to request all hindcastDates of a hindcastMonth, in one request, like the example below.
- you can use the variable target to write the requested data as you wish. In the example below the data is written per leveltype (sfc, pl) per hindcastMonth.
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