14 years of Absolute calibration of satellite altimeters on Lake Issykkul from GPS field campaigns

Jean-Francois Cretaux (CNES/LEgos, France)

CoAuthors

Muriel Berge-Nguyen (Legos/CNES, France); Stephane Calmant (Legos/IRD, France); Pascal Bonnefond (SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, LNE, France); Nurzat Jamangulova (IWPH, Kyrgyzstan); Rysbek Satylkanov (IWPH, Kyrgyzstan); Florent Lyard (Legos/CNRS, France); Felix Perosanz (Get/CNES, France); Philippe Maisongrande (Legos/CNES, France)

Event: 2018 Ocean Surface Topography Science Team Meeting

Session: Regional and Global CAL/VAL for Assembling a Climate Data Record

Presentation type: Type Oral

Within the framework of Jason-2 mission, a Cal-Val project including continental waters (Rivers and lakes) had been setup in 2007. It includes installation of permanent site (meteo station, limnigraphs, GPS reference point) and regular field campaign for the whole lifetime of the satellite. The lake Issykkul in Kyrgyzstan has been chosen as site dedicated to lakes following a preliminary project in 2004 on this lake. It is funded by CNES.
Over the last decade more and more scientific studies were using satellite altimetry to monitor inland waters. However, linking time series from different missions require to accurately monitoring the biases and drifts for each parameter contributing to the final estimate of the reflector height. Moreover the calibration of satellite altimetry over ocean does not apply to inland seas (e.g., corrections, retracking, geographical effects).
Regional Cal/Val sites supply invaluable data to formally establish the error budget of altimetry over continental water bodies, in addition to the global mission biases and drift monitoring. It allows checking
if specific conditions lead to different estimation of absolute bias of the instruments. Calibration over lakes surfaces for example has interesting characteristics with respect to ocean surface: wave and ocean tides are generally low, and to summarize, dynamic variability is much smaller than in the oceanic domain.
CAL/VAL activities on the oceanic domain have a long history and protocols are well established. CAL/VAL activities on lakes are more recent but in turn they address other problems such as the performance of the various tretracking algorithms and more globally assess the quality of the geophysical corrections. This is achievable when measurements of specific and numerous field campaigns and ground permanent network of level gauges and meteo stations are processed to detect biases, errors in the geophysical corrections, etc. 15 campaigns with GPS receivers have been conducted on Issykkul lake (2004, 2005, and every year from 2008 to 2017), with receivers installed on a boat, and receivers on the shore. Cruise with GPS data along the ground track of each satellite were conducted. They allow estimating absolute bias of each altimeter, and relative bias between them. We present here a summary of the reseach and results obtained over the last 14 years using the cal/val site of lake Issykkul. It includes all altimeters of the Jason series, the Envisat and Saral, the Sentinel-3A.
 

Oral presentation show times:

Room Start Date End Date
Teatro Auditorium Fri, Sep 28 2018,10:15 Fri, Sep 28 2018,10:30
Jean-Francois Cretaux
CNES/LEgos
France
jean-francois.cretaux@legos.obs-mip.fr