AMMA-SAT file format

Files are in Netcdf Format.

File content

A file contains only one geophysical parameter (and eventually associated statistical data) for one sensor and one platform. Orbits of same type (ascending, descending, AM or PM) are grouped into one file per day, on a regular lat/long grid.

File Naming Convention

"P_I_S_Z_R_T_YYYY[MM[DD]]_[HH[MM]]_vV1-V2".nc
with :
P: Geophysical parameter,
I: Sensor,
S: Platform,
Z: orbit type (asc: ascending, desc: descending),
R: Spatial Resolution (ex: 025d --> 0.25 degrees),
T: Temporal Resolution (ex : 01mth for monthly data),
YYYY[MM[DD]]: Year, Month (Optional), Day (Optional),
[HHMM]: Reference time of the data (Optional),
V1: originating dataset version,
V2: dataset version in the AMMASAT database,
.nc ---> Netcdf file suffix.

Example: albedo-nir_polder-1_adeos_010d_10day_199611_v5.0-02.nc

This file contains 10-Days Near-Infrared albedo product with a 0.1° spatial resolution estimated from the Polder-1 sensor data, onboard Adeos, for thez month of November, 1996, in version 5.0 for the initial dataset and in version 02 for the AMMASAT database after netcdf conversion.

Netcdf File Description

Dimensions:

  • time: number of time step,
  • lon: number of longitude points,
  • lat : number of latitude points,
  • level (optional): Number of levels or distinction between ascending and descending orbits
  • bxnum: number of AMMA cells.
  • lenght : maximum length of AMMA Cells names

Coordinates variables:

  • time: time coordinate, expressed as a number of days since 01/01/1960,
  • delta_t : Temporal resolution (format : YYYY-MM-DD HH:MM:SS)
  • lon: longitude coordinate of pixel center, expressed in degrees east,
  • lat: latitude coordinate of pixel center, expressed in degrees north.

Variables:

  • data: geophysical parameter,
  • tpix (optional): time of each pixel expressed in minutes since the reference time of the file (given by time),
  • bxdata: number of pixels in each AMMA cell,
  • bxtimemin, bxtimemax: minimum and maximum time in each AMMA cell,
  • bxlonmax, bxlatmax, bxlonmin, bxlatmin: definition in latitude/longitude of each AMMA cell.

Attributes of data, tpix et bxtime variables:

  • add_offset and scale_factor:

The variables data, tpix, bxtimemin and bxtimemax are stored on 1 byte (signed integer). You have to apply the following formula to retrieve the geophysical value (in float) from the stored value in the file :
geophysique_value = scale*stored_value + offset
The scale factor and offset are given as attributes of each concerned variable.

  • valid_range: valid variation range of variable, same type of the uncompressed value,
  • actual_range: variation range of variable for the file, same type of the uncompressed value,
  • units : variable units,
  • missing_value: code for the missing value, same type as the compressed value,
  • _FillValue: fille value for the CF convention, same type as the compressed value.

Last Updated ( Thursday, 20 April 2006 )