Cryosphere

Ice validation for Antarctic and Greenland continents. CTOH investigates the stability and reliability of different corrections for the altimetric measurements. A validation chain is already developed specifically to the cryosphere (ICE validation).

Principle of the Ice Validation

Here we show the processing chain that has been developed at LEGOS and which we use to qualify the ENVISAT and ERS data. We show the steps of the validation process, the results on various parameters, like height, but also backscatter, leading edge and trailing edge of the waveforms. The validation process allows us to deliver reports, but also a validation table which is available on our website as well as other meta product.

 

ENVISAT re-processing release v2.1

 

The validation of the latest reprocessing (v2.1) of ENVISAT data over the cryosphere for the period from June 2002 (Cycle 6) up to october 2010 (Cycle 94). This dataset cover the period until the orbit change in October 2010.

 

Validation table

 

    The ice validation table gives a global view of the mission over an area (Antarctica or Greenland) of the availability of tracks. The colour code gives the information of the major events met during the validation process (like the tracks missing, the tracks validated or not, …).

 

Quality assessment report -Annual-

 

    The quality assessment report describes long term monitoring of validated data over cryosphere. It merges the informations from each cycle and gives a global vision of the ICE-2 parameters and corrections behaviour during the mission. It will be available by the end of october.

 

Particular investigations

 

Here are all collected the investigations done about the validation data for the ENVISAT mission.

 

Doppler slope correction

With the previous processing, the ICE Validation chain of the CTOH detects some problems with the Doppler slope correction over the Cryosphere. Here we present validation of the latest re-processing (v2.1) of ENVISAT data over the cryosphere and show the improvements.

 

Dry tropospheric correction 

There are two studies about this correction. One concerning the previous ENVISAT GDR release and the other one concerning the last release ENVISAT GDR (v2.1).

Here we present the validation of the latest reprocessing (v2.1) of ENVISAT data. We observe the limitation of this re-processed DTC, especially the jump observed at cycle 44 over Antarctica which causes significant local trend and suspect changes in the variability of this correction over time. We investigated a solution and re-compute this correction all over the globe with the ERA Interim ECMWF pressure fields and using directly the altimetric range measurement rather than any external digital elevation model (DEM). We present the results of this investigation, the statistics of previous (DTC_v2.1) and new corrections (DTC_ctoh) and in the context of different surfaces. The improvement is significant, and we discuss the aspects and impacts of this improvement, in terms of meteorological-fields, procedure, and location.

 

This investigation looked at the use of the Dry Tropospheric Correction over Antarctic ice sheets in the Envisat GDR v2.1 data set (cycles 10-­‐93), reprocessed during 2011. A.S. Muir Mullard Space Science Laboratory, UCL 28/11/2011.

 

    Technical note ESA

 

ENVISAT RA2 Dry Troposphere correction for ice sheets, ESA Living Planet Symposium, 28 June - 2 July 2010, Bergen, Norway. 

ERS-1 and ERS-2

 

The CTOH is engaged in reprocessing project for these missions ERS-1 and ERS-2.