UM Climate Meaning

Climate Means

The UM has a mechanism for automatic resubmission (see UM AutomaticResubmission) so the model can be run for a very long time. The model run is divided into suitably sized chunks which fit in with the batch queuing structure of the computer on which it is running. As the run progresses restart files (dumps) are output at regular intervals to enable the run to be restarted at the start of each new chunk or in the event of a computer crash during a particular chunk. The basic unit of time of the UM is the 'dump frequency'.

The UM climate meaning system enables the calculation of means of data over very long periods, years or even decades. STASH cannot sensibly do means for such long periods because of a loss of precision as the partial sums become much larger than the data which is being added to the sum. Climate means overcome this problem by meaning the mean periods so that accuracy can be preserved.

Data from diagnostic fields are sampled every dump period. The means of this data are calculated and output at the end of period 1, which has been defined in the climate mean system. Period 2 means, set up by the climate meaning system, are then defined as multiples of period 1. Up to four meaning periods can be selected. For example, in a climate run with dumps produced every 10 days using a 360 day calendar, period 1 means could be three restart dumps to produce monthly means and period 2 means could be three period 1 means giving seasonal means. Four period 2 means would give an annual mean and ten period 3 means would provide a decadal mean.

Setting up climate means in the UMUI

  1. In the UMUI window model selection → atmosphere → control → post processing, meaning and dumping → dumping and meaning
    For 360 day climate runs:
    • set regular frequency dumps with possible meaning sequence.
    • set the dumping frequency restart dumps every....
  1. Click NEXT, to define further requirements. Here specify the following
    • the number of climate meaning periods to use, in this example 3
    • the period length, which will depend on the dumping frequency set. If the dumping frequency is every 10 days then for monthly, seasonal and yearly means use 3, 3 and 4 (3x10day, 3x30days and 4x90days). For Gregorian-calendar climate means, the only periods available are months, seasons and years. It is not compulsory to choose all 3 periods. Do not select zonal-mean prints with Gregorian means, as the numbers may be incorrect, although the option does work.

  1. Setup STASH
    Any diagnostic can have any number of processes applied to it at a frequency of one time step to the dump frequency. The value in the dump can be further meaned over a different meaning period. To use climate meaning you will need to specify the diagnostic in STASH and for each diagnostic selected
    • set up the time profile with the following options:
      specify time mean
      specify the sampling frequency, this is how often you want to take a sample of the diagnostic for meaning.
      specify the output times, this is how often the diagnostic is produced.
    • set up the usage profile
      specify that you want to mean over a meaning period in addition to any meaning over a dump frequency by selecting Dump store with climate mean TAG
      specify which of the (up to 4 ) meaning periods the diagnostic should be meaned over

The climate meaning system is called only at the end of a dump period; therefore it usually makes sense that the STASH output time matches the dumping period exactly - a warning will be given if a climate meaned diagnostic is attached to a time profile that does not match the dumping period.

Check how often the files are reinitialised in model selection → (sub model independent →) post processing → initialisation and processing of mean & standard PP files

Climate Mean Files

Restart dumps have file names of the form: $RUNID.daj34e0
Model diagnostic monthly files have names of the form: $RUNID.paj3may

In general restart dumps are deleted when a new one is produced. This option is set via the UMUI in window model selection → (sub model independent →) post processing → main switch

  • Set automatic post processing required to "yes"
  • Select delete superseded restart dumps

When climate meaning is enabled partial sum mean dumps are produced which have names like $RUNID.apstmp1 (for atmospheric fields). These files are in temporary directories which should be deleted automatically at the end of a run but if the run stops part way through they should get copied to a permanent directory.

At the end of every period1 climate meaning time length the completed period 1 partial sum dump is copied to the period 2 partial dump which has file name like $RUNID.a_s2a ( for atmospheric fields). These files are not routinely removed as they are in permanent directories.

The climate mean files have names of the form:

$ 10 day means
$ monthly means
$ seasonal means
$ yearly means
$RUNID.m1.. period 1 means if they are not one of the above

Last modified 2 years ago Last modified on 17/04/15 11:52:11