Minimize Sea ice re-tracking

There is a single re-tracker dedicated to SAR mode sea-ice waveforms. This re-tracker method has its heritage in the empirical-based sea-ice re-tracker implemented in the CryoSat-2 mission. It corresponds to a simplified version of the 5-sections ice-sheet retracker used in CryoSat-2. In this case only three segments are considered: leading edge is modelled as a Gaussian; an exponenetial function is used to fit the trailing edge decaying; and a third order polynomial function.

The main output of these two retrackers annotated in the Level-2 product are:

  • corrected "sea-ice" altimeter range
  • corrected "sea-ice" backscatter coefficient
  • "sea-ice" sea surface height
  • "sea-ice" sea surface height anomaly
  • interpolated "sea-ice" sea surface height anomaly
  • freeboard (difference between the measured surface height and the expected sea-surface height at the given location)
 
 

PARAMETER

Surface Type Classification Derived from Altimeter

NETCDF NAME

surf_type_class_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band

DESCRIPTION

The ALT_MAN_WAV_02 algorithm discriminates waveforms assigning a surface type classification based upon the record contents. The possible surface types are: open ocean (0b), sea_ice (1b), lead (2b) and unclassified (3b).

UNITS

 

DATA SET AVAILABILITY

Reduced: none
Standard: 20 Hz Ku band
Enhanced: 20 Hz Ku band

OPERATING MODE AVAILABILITY

SAR

DATA ORIGIN

1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_MAN_WAV_02 algorithm
20 Hz C-band: none

ADDITIONAL INFORMATION

None

PARAMETERS RELATED

None

PARAMETER DETAILED DESCRIPTION

ESA's Global Land and Ocean Mission for GMES Operational Services

Table 1. Discrimination parameters

 

 

PARAMETER

Corrected Sea-Ice Backscatter Coefficient

NETCDF NAME

sig0_sea_ice_sheet_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band

DESCRIPTION

SAR mode: sea-ice retracking.
The instrumental corrections already included are: AGC instrumental errors correction (agc_cor_[x1]_[x2]), internal calibration correction (sig0_cal_[x1]_[x2]). The ALT_PHY_BAC_02 algorithm computes the backscatter coefficient for SAR mode.

UNITS

10-2 dB

DATA SET AVAILABILITY

Reduced: none
Standard: 20 Hz Ku band
Enhanced: 20 Hz Ku band

OPERATING MODE AVAILABILITY

SAR

DATA ORIGIN

1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_PHY_BAC_02 algorithm
20 Hz C-band: none

ADDITIONAL INFORMATION

None

PARAMETERS RELATED

None

PARAMETER DETAILED DESCRIPTION

ESA's Global Land and Ocean Mission for GMES Operational Services

Table 2. Sea-ice re-tracking estimates - Backscatter coefficient

 
 

PARAMETER

Corrected Sea-Ice Altimeter Range

NETCDF NAME

range_sea_ice_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band

DESCRIPTION

SAR mode: sea-ice re-tracking using the ALT_RET_ICE_03 algorithm.
The ALT_RET_ICE_03 algorithm re-tracks the power waveform by fitting a function that models the expected power return to the waveform. ALT_COR_RAN_02 computes the general Doppler correction.
The instrumental corrections already included are: USO drift correction (uso_cor_[x1]_[x2]), internal path correction (int_path_cor_[x1]_[x2], distance antenna-COG (cog_cor_[x1]_x2]) and Doppler slope correction (dop_slope_cor_[x1]_[x2]).

UNITS

10-4 m. An offset of 700 000 m to be added to the value read from the netCDF file.

DATA SET AVAILABILITY

Reduced: None
Standard: 20 Hz Ku band
Enhanced: 20 Hz Ku band

OPERATING MODE AVAILABILITY

SAR

DATA ORIGIN

1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_COR_RAN_02 algorithm
20 Hz C-band: none

ADDITIONAL INFORMATION

None

PARAMETERS RELATED

None

PARAMETER DETAILED DESCRIPTION

ESA's Global Land and Ocean Mission for GMES Operational Services

Table 3. Altimeter range

 
 

PARAMETER

Sea-Ice Sea Surface Height and Sea-Ice Sea Surface Height Anomaly

NETCDF NAME

sea_ice_sea_surf_[x1]_[x2]
sea_ice_sea_ssha_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band

DESCRIPTION

SAR mode: sea-ice re-tracking using the ALT_RET_ICE_03 algorithm.
The ALT_RET_ICE_03 algorithm re-tracks the power waveform by fitting a function that models the expected power return to the waveform. ALT_PHY_RAN_02 computes the sea surface height anomaly for sea-ice.
The instrumental corrections already included are: USO drift correction (uso_cor_[x1]_[x2]), internal path correction (int_path_cor_[x1]_[x2]), distance antenna-COG (cog_cor_[x1]_x2]) and Doppler slope correction (dop_slope_cor_[x1]_[x2]).

UNITS

10-4 m

DATA SET AVAILABILITY

Reduced: none
Standard: 20 Hz Ku band
Enhanced: 20 Hz Ku band

OPERATING MODE AVAILABILITY

SAR

DATA ORIGIN

1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_PHY_RAN_02 algorithm
20 Hz C-band: none

ADDITIONAL INFORMATION

None

PARAMETERS RELATED

Interpolated Sea-Ice Sea Surface Height Anomaly: int_sea_ice_sea_ssha_[x1]_[x2]
Freeboard: Freeboard_[x1]_[x2]

PARAMETER DETAILED DESCRIPTION

ESA's Global Land and Ocean Mission for GMES Operational Services

Table 4. Ocean surface parameters