HIRLAM Model Data Format (KNMI)

The data this page describes are here.

Each data file consists of the output over each of the three Cloudnet sites for one run of the model. The model is run every six hours, so there are four files per day, and each run produces forecasts every three hours from T+0 to T+48. In addition to the variables at the nearest gridpoint to each site, the variables from the eight nearest gridpoints are also reported, in the form of a 3×3 grid. The filenames are of the form cloudnet.YYYYMMDDHH, where YYYYMMDD is the date and HH is the forecast time. They are zipped up into monthly archives with names of the form HIRLAM_YYYYMM.zip.

                HIRLAM [analysis time of forecast]
                                 -------------
                                 | 1 | 2 | 3 |    Layout
                                 -------------      of
                                 | 4 | 5 | 6 |
                                 -------------     the
                                 | 7 | 8 | 9 |    area
                                 -------------
For forecast period 00 03 06 09 12 15 18 21 24 27 30 33 36 39 42 45
        Forecast [forecast period]
        CHIBOLTON [latitude longitude]
        single level data
    6 105   0   Geopotential of the surface     m2/s2
   83 105   0   Roughness length of surface     m
    1 105   0   Pressure at surface             Pa
    1 103   0   Pressure at mean sea level      Pa
   11 105   0   Skin temperature of surface     K
   11 105   2   2 meter temperature             K
   31 105  10   Wind direction at 10 meter      degree w.r.t. true N
   32 105  10   Wind speed at 10 meter          m/s
   51 105   2   Specific humidity at 2 meter    g/g
   17 105   2   Dew point temperature at 2 m    K
   62 105   0   Large scale precipitation       kg/m2
   63 105   0   Convective precipitation        kg/m2
   71 105   0   Cloud cover                     0 .. 1
        multilevel data
        For level 31 .. 1
     11      Pressure   Pa      temperature             K
        For level 31 .. 1
     31      Pressure   Pa      wind direction  degree w.r.t. true N
        For level 31 .. 1
     32      Pressure   Pa      wind speed              m/s
        For level 31 .. 1
     39      Pressure   Pa      vertical velocity       Pa/s
        For level 31 .. 1
     51      Pressure   Pa      specific humidity       g/g
        For level 31 .. 1
     76      Pressure   Pa      cloud water             g/g
        PALAISEAU [latitude longitude]
        [idem]
        CABAUW [latitude longitude]
        [idem]

The 9-squre indicates the correspondence between column number and
sub-area; column 5 always corresponds with the subarea in which the
given lat/lon coordinates fall.

The multilevel data need a pressure coordinate, because the height of
the coordinate surface varies with ground level (so called eta
coordinates).

Note also:

• The horizontal model resolution is around 22 km; thus the position of the adjacent gridpoints can be calculated.
• The division between liquid and ice water content is internal to the model, so it is not possible to extract them separately.
• The model does not report cloud fraction at each level. For more information on the cloud scheme, read pages 28 and 29 of the HIRLAM scientific documentation (postscript).