Absolute calibration of SARAL-AltiKa and Jason-2 over Kavaratti Island in Arabian Sea

K. N. Babu (SAC, India)

CoAuthors

A. K. Shukla (ISRO, India); A. B. Suchandra (ISRO, India); Pascal Bonnefond (OCA/GEOAZUR, France); P. Mehra (National Institute of Oceanography, Goa, India)

Event: 2014 Ocean Surface Topography Science Team Meeting

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

Presentation type: Type Oral

The equatorial altimeter calibration site "Kavaratti Island" has historic tidal observations: started with Survey of India, National Institute of Oceanography, and Indian national Centre for Ocean Information Services. However these observations are independent interms of its sampling location and time. In order to perform the absolute calibration of altimeters two of its radar gauge bench marks are leveled to Topex ellipsoid reference frame through a geodedic survey in October 2012 and later in September 2013. Permanent GPS receiver installation as well as GPS buoy experiment was part of these survey. The absolute calibration result of Jason-2 as well as Saral/AltiKa for the period 12th February 2009 to 20th February 2014 is analyzed and reported here.

The bias between tide gauge measured sea surface height and altimeter measurement with an identical referencing frame is defined here as the calibration parameter. By using the site characteristics parameters which are derived from GPS survey, the tide gauge observations are converted into identical altimeter sea surface height. The geo-location corrections are compensated using the geoid gradient parameter.

The absolute sea surface bias for Jason-2 is -1.52mm/18.9mm at tide gauge station 1 / 2 with standard deviation of 41.47mm / 36.47mm. The absolute bias for the collocated time frame (12/10/2012 - 13/11/2013) is 2.55mm/17.93mm with standard deviation of 36.10mm/37.79mm. The absolute calibration exercise of AltiKa for its 11 cycles at tide gauge station 2 shows an absolute bias of -17mm.
 

Oral presentation show times:

RoomStart DateEnd Date
Ballroom Wed, Oct 29 2014,14:15 Wed, Oct 29 2014,14:30
K. N. Babu
SAC
India
kn_babu@sac.isro.gov.in