Data Processing Methods

Edited: 2013-01-21


The table below describes the parameters used in computing the global mean sea level.

Parameter TOPEX Jason-1 Jason-2
Time Period 1992-12-06 to  2002-01-10
2002-01-15 to 2008-07-02
2008-07-03 to present
Cycles 8-343
Base Data Set MGDR-B GDR-C GDR-D
Orbit STD0905 (Lemoine et al., 2010) GDR
Range & Corrections  
Waveform Tracker GDR GDR MLE-4
Dry Troposphere GDR (from ECMWF)
Wet Troposphere  TMR (Replacement Product v.1.0)
 GDR-C (Cycles 1-227); JMR Replacement Product (Cycles 228-259)  AMR (GDR)
Ionosphere GDR (not smoothed)
Sea State Bias CLS Collinear v. 2009 (Tran et al., 2010 GDR
Center of Gravity  MGDR-B N/A
Mean Sea Surface & Corrections
Mean Sea Surface CLS01
Ocean Tide & Loading Tide GOT4.7 (Ray, 1999)
Long Period Equilibrium Tide Cartwright & Tayler, 1971, Cartwright & Edden, 1973
Solid Earth Tide  GDR (Cartwright & Tayler, 1971; Cartwright & Edden, 1973)
Pole Tide GDR (Wahr, 1985)
Atmospheric Pressure (Inverted Barometer) AVISO Dynamic Atmosphere Correction (DAC) that combines MOG2D high frequency and inverted barometer low frequency signals (Pascual et al., 2008)
Glacial Isostatic Adjustment (GIA) -0.3 mm/yr (Peltier, 2001, 2002, 2009; Peltier & Luthcke, 2009)
Processing Corrections  
Inter-Mission Bias  88.48 mm (TOPEX to Jason-1)
 -100.82 mm (Jason-1 to Jason-2)
Minimum Ocean Depth  120 m
Outlier Removal
anomaly greater than 2 m 


Global mean sea level

We chose to reference TOPEX and Jason SSH anomalies on the common ground-track to an along-track mean computed by the CLS_01 mean sea surface [1]. Each cycle of T/P and Jason data are referenced to a standard set of locations using a cross-track gradient correction. Global mean sea level was computed from the corrected SSH anomalies using a simple equal-area weighted average [2]. See our calibration paper (Leuliette, E. W., R. S. Nerem, and G. T. Mitchum. "Calibration of TOPEX/Poseidon and Jason Altimeter Data to Construct a Continuous Record of Mean Sea Level Change." Marine Geodesy 27, no. 1 (2004): 79.) for more information.