ECMWF DDH Data Format

The data this page describes are here.

The data for each Cloudnet site consist of five ASCII files per day, with names of the form cloudnet_YYYYMMDD_AAA_BB, where YYYYMMDD is the date, BB is a numerical code that identifies the site and AAA is one of var (variables on model levels), flx (fluxes between levels), or sfc, sfc2 and sfce (surface and single-level fields).

Each file has a three line header, with each line beginning with "#". The first line explains the second. The first four parameters on the second line are model internal parameters and are irrelevant for the user. The next two numbers mark model point for which the data was extracted. The third line contains the variable names for each of the columns of data that follow. The first four columns are common to all files: idat and itime are the initial date and time of the forecast from which the data was retrieved. vdate and vtime are the verifying date and time of the data meaning date and time which it is valid for. Hence the difference to the initial date and time indicates the forecast range used. The next column (lev) is the model level of the data. The columns that follow these are specific to the file type:

*var*

These files contain the model variables on the 60 model levels. Level 1 is the top full level of the model (10 hPa), level 60 is the lowest full level. The order of the variables is:

P HIST - pressure (Pa)
U HIST - zonal wind component (m/s)
V HIST - meridional wind component (m/s)
T HIST - temperature (K)
Q HIST - specific humidity (kg/kg)
L HIST - specific cloud liquid water content (kg/kg)
I HIST - specific cloud ice content (kg/kg)
A HIST - cloud fraction (percent/100.)
R HIST - reative humidity (percent/100.)
W HIST - omega=vertical velocity in pressure coordinates (Pa/s)

*flx*

These files contain the radiative, turbulent, and precipitation fluxes throughout the atmosphere. The fluxes are averages over the last hour.

They are archived on the so-called flux levels of the model (often referred to as half-levels). The full levels on which the variables are stored are placed between two flux levels. Hence, level 61 represents the surface and level 1 the top of the atmosphere. Full level k is between half level k and k+1. The fluxes in level 61 are the surface fluxes. The order of the fluxes is:

T FSWR - net shortwave flux (W/m²)
T FLWR - net longwave flux (W/m²)
T FVDF - sensible heat flux (W/m²)
Q FVDF - turbulent moisture flux (kg/kg * kg/(m²*s))
Q FCVR - convective rain flux (kg/(m²*s) = mm/s)
Q FCVN - convective snow flux (mm/s)
Q FLSR - large-scale rain flux (mm/s)
Q FLSN - large-scale snow flux (mm/s)
U FVDF - turbulent momentum flux - u component (m/s * kg/(m²*s))
V FVDF - turbulent momentum flux - v component (m/s * kg/(m²*s))

*sfc*

These files contain surface/single-level variables and fluxes. The level number is set to 1. The order is:

SFSSLHF - Surface latent heat flux (W m^-2)
SFSSSHF - Surface sensible heat flux (W m^-2)
SFSSW - Surface solar radiation (W m^-2)
SFSLW - Surface thermal radiation (W m^-2)
SFSWC - Surface csky solar radiation (W m^-2)
SFLWC - Surface csky thermal radiation (W m^-2)
SFLSR - Large-scale rainfall (kg m^-2)
SFSCR - Convective rainfall (kg m^-2)
SFLSF - Large-scale snowfall (kg m^-2)
SFSCF - Convective snowfall (kg m^-2)
SFSTCC - Total cloud cover
SFSLSPF - Large-scale precipitation fraction
SFSSWDO - Downward Solar (kg m^-2)
S HIST - Surface pressure (Pa)

*sfc2*

These files also contain surface variables and fluxes (there are too many to fit in one file). The order is:

SFSLWDO - Downward thermal radiation (W m^-2)
SFSZ - Orography as a geopotential (m² s^-2)
SFSLF - Land fraction
S HIST - Surface pressure (Pa)

*sfce*

Yet more surface variables and fluxes:

SFST2M - 2 m temperature (degrees C)
SFSQ2M - 2 m specific humidity (g/kg)
SFS10U - 10 m zonal wind (m/s)
SFS10V - 10 m meridional wind (m/s)
SFSZ0M - Surface Roughness for momentum (m)
SFSZ0H - Surface Roughness for heat (m)
SFSAL - Surface albedo (%)
SFSBLH - Boundary layer height (m)
SFSTSK - Skin temperature (degrees C)

Note:

Very small numbers (<10^-10 for precipitation and < 10^-1 for radiation) and small negative numbers in solar radiation and precipitation are due to packing and unpacking mechanisms and do not represent model problems.