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First you need to understand how the S2S data is organised in MARS. 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)
- dates Hdates (2015-01-01 or 2015-01-05 or 2015-01-08, ...)
- time-steps
- members (for perturbed forecast)
 The idea is to have in the same tape file, all time-steps, all members, all parameters for a type of level, a type, a dateHdate
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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 dateHdate.  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 dates 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
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Hdates for a CMA request?
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| title | The main idea in brief: |
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for dateHdate in dateHdate-list
your-s2S-request (includes the levels, parameters, steps etc(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 yearHdate from 2010-03-01 to 2010-03-31
call your-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
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Hdays for several
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Hyears ?
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| title | The main idea in brief: |
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forThe yearbest inapproach yearsis (firstlyto iterate over years)
the Hyears you wish. forFor montheach in months (secondly Hyear iterate over monthsall ofHmonths theand year)
for each Hmonth iterate over all its Hdays.
for daysHyear in daysHyears (thirdly
iterate over the daysfor ofHmonth thein month)Hyear
for Hdays in Hmonth
your-request (includes the levels, parameters, steps etc) |
An example to request Control forecast, sfc, for years 2010-2014 for 2 months (eg April and June)
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| title | The main idea in brief: |
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for each year from 2010Hdate to 2014= Hyear-Hmonth-Hday for months April, June
your-s2S-request (Hdate) |
What is the best approach to get all
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Hdays for several
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Hyears and
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Hmonths and for several
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hindcasts ?
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| title | The main idea in brief: |
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for yearHyear in years (firstly iterate over years)Hyears
for monthHmonth in months (secondly iterate over months of the year)Hyear
for daysHdays in days (thirdly iterate over the days of the month)Hmonth forHdate = Hyear-Hmonth-Hday hindcast in hindcasts your-S2S-request (includes the levels, parameters, steps etc)(Hdate) |
An example to request Control forecast, sfc, for
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Hyears 2010-2014 for 2
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Hmonths (eg April and June)
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| title | The main idea in brief: |
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for each yearHyear from 2010 to 2014 for monthsHmonth in April, June for Hday in your-request
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An example to request Control forecast, pressure levels, for years 2010-2014 for 2 months (eg April and June)
Hmonth |
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| title | The main idea in brief: |
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for each year from 2010 to 2014 for monthsHdate April, June= Hyear-Hmonth-Hday for each hindcast date
your-request
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old below:
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cf and pf are stored separately.
For pf is not efficient to do:
HDATE HHdate = 20040101/20040106/20040111/20040116/20040121/20040126/20040201/20040206/20040211/20040216/20040221/20040226/20040301/20040306/20040311/20040316/20040321/20040326/20040401/20040406/20040411/20040416/20040421/20040426/20040501/20040506/20040511/20040516/20040521/20040526/20040601/20040606/20040611/20040616/20040621/20040626/20040701/20040706/20040711/20040716/20040721/20040726/20040801/20040806/20040811/20040816/20040821/20040826/20040901/20040906/20040911/20040916/20040921/20040926/20041001/20041006/20041011/20041016/20041021/20041026/20041101/20041106/20041111/20041116/20041121/20041126/20041201/20041206/20041211/20041216/20041221/20041226,
NUMBER = 1,
but it is more efficient to group all members in one go for fewer datesHdates:
HDATE HHdate = 20040101/20040106/20040111/20040116/20040121/20040126,
NUMBER = 1/to/50
This implies less positioning and more contiguous reads.
We could look at increasing the 10GB limit. We have more hardware and are in a better position to handle bigger chunks.
For the 3 allowed streams, I would extract different type/levtype in different streams. For instance:
a) 1 stream: pf/sfc
b) 1 stream: pf/pl
c) 1 stream: cf/sfc and when it finishes,cf/pl
and I would put 2 requests for each stream above. Once a request finishes and starts the downloading, the next request will kick in, and it will find in many cases that the tape volume is still in the tape drive, which will save in avg 2 minutes for a tape mount.
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An example to request Control forecast, pressure levels, for
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Hyears 2010-2014 for 2
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Hmonths (eg April and June)
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| title | The main idea in brief: |
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for each yearHyear from 2010 to 2014 for monthsHmonths April, June
for each hindcast dateHdate
your-request
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old below:
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