Documentation

File Format

CM SAF's climate monitoring HOAPS products are provided as NetCDF (Network Common Data Format) files. The data files are created following NetCDF Climate and Forecast (CF) Metadata Convention version 1.5 and NetCDF Attribute Convention for Dataset Discovery version 1.0. For data processing and conversion to various graphical packages input format, CM SAF recommends the usage of the climate data operators (CDO), available under GNU Public License (GPL) from MPI-M.

Naming conventions

The data sets are delivered in separate files for each averaging period:
- 1 file per month for monthly means (HOAPS-G)
- 1 file per 6 hour for composites (HOAPS-C)

The naming convention for files received from the CM SAF Web User Interface is structured as follows:

PPPTTYYYYMMDDhhmmXXXXXXXXXXVVRR.nc

PPP CM SAF parameter code (see ››see "HOAPS Code Table")
TT product type: "mm" - monthly mean / "ic" - instantaneous composite data
YYYY year
MM month
DD day
hh hour
mm minute
ss second
XXXX internal product code
VV CM SAF version code
RR selected region: "GL" - global / "UD" - user defined

Example filenames:

  • PREic200112311800001130034201GL.nc
    composite file for 2001-12-31 18hr timestep, global domain
  • PREmm200211010000001130034201GL.nc
    monthly mean file for 2002-11-01, global domain
  • PREmm200801010000001130034201UD.nc
    monthly mean file for 2008-01-01, user defined domain

Decoding of Parameters

In order to save disk space, all time dependent 2-dimensional fields are stored with netCDF data type short (16 Bit). The encoding/decoding follows the standard netCDF conventions. If the attributes scale_factor and add_offset are present for a variable, the data has to be scaled first and then the offset is added. Missing values have to be filtered before decoding.

Variables

Each netCDF datafile contains the following variables (unless otherwise noted):

show/hide variable list


Variable attributes

The netCDF variables can contain one ore more of the following attributes:

show/hide attribute list


Global attributes

Each netCDF datafile contains the following global attributes:

show/hide attribute list

HOAPS Code Table

AcronymDescriptionUnitPar. IDCM SAF IDCM SAF code
WINDWind speed at 10m heightm/s0CM-142NSW
HAIRNear surface specific humidityg/kg1CM-141NSH
RAINPrecipitationmm/d2CM-144PRE
WVPAVertically integrated water vapourkg/m**23*HTW
TWPAVertically integrated total (ice+liquid) waterkg/m**24*TWP
ASSTSea surface temperaturedeg C30*SST
HSEASea surface saturation specific humidityg/kg31*SSH
FNETSurface net longwave radiationW/m**260*SNL
DHUMDifference in humidityg/kg61*SHD
TRCELatent heat transfer coefficient (Dalton number)-64*LTC
LATELatent heat flux at sea surfaceW/m**265CM-143LHF
HEATSensible heat flux at sea surfaceW/m**266*SHF
EVAPEvaporationmm/d67CM-145EVA
BUDGFreshwater fluxmm/d68CM-146EMP
      * parameter not operationally supported by CM SAF