SNAP documentation

Experiment starting times

The aim of this project is to compare stratospheric data for different models. 15 day runs have been performed for a range of ensembles for the following starting times

  • Northern hemisphere
    • 23 December 2012
    • 28 December 2012 (or 29 December 2012 for METO)
    • 02 January 2013
    • 07 January 2013
    • 12 January 2013
  • Southern hemisphere
    • 05 October 2012
    • 10 October 2012
    • 15 October 2012
    • 20 October 2012
    • 25 October 2012

Re-processing the data

The data has been re-processed to make it easier to compare the data sets, and the following changes have been made

  • variable names have been altered, so that they should be consistent across data sets. Where possible, the variable names have been matched to the names used in the ERA-Interim datasets.
  • most variables have been converted to floats (also known as single precision reals, 4 bytes, or REAL*4). The exceptions are a few variables representing dimensions which are integers (also 4 bytes per element).
  • Ensure that latitude runs from 90° to -90° and pressure levels run from lower in atmosphere to higher for all datasets.
  • Data for each starting date, for each ensemble are put into one file. The naming convension for these files is /group_workspaces/jasmin/snap/nc/phase1/<hemisphere>/<organisation>/<start_date>/<organisation>_<start_date>_<ensemble>.nc where <hemisphere> is either `nh_ssw' or `sh_fw', <organisation> is the organisation, <start_date> is the start date and <ensemble> is a two digit number indicating which ensemble.

More detailed information on the processing for each data set can be found on the pages for CAWCR, KOPRI, METO and MRI.

A summary of the data produced is given in the table below

OrganisationRange of time (in days from start) Resolution (Δlat, Δlon) Number of points (nlat, nlon) Pressure levels (upper pressure levels) Theta levels
CAWCR0.25 - 15(1.5°,1.5°) (119, 240)37 (15)5
KOPRI0 - 29 (1.9°,1.875°) & (2.5°,2.5°) (94, 192) & (73, 144)17
METO0 - 30(5/9°,5/6°) (324, 432) & (325, 432)37
MRI0 - 15.75(1.5°,1.5°) (121, 240)37 (15)5

Where there are 37 pressure levels, these are always 1000, 975, 950, 925, 900, 875, 850, 825, 800, 775, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 225, 200, 175, 150, 125, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2 and 1 hPa, where the bold numbers show the levels also found in the KOPRI data. The units here of hPa although the units in the datasets are all Pa.

The upper pressure levels are the top 15 levels, so 200hpa to 1hPa.

The theta levels are at 340, 650, 840, 1450 and 1850K.

From the table it's clear that while the 1.5° by 1.5° lat-lon grid is the most common, not all data is on this grid. The other datasets can be moved onto the grid with the remapLatLon executable.

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