POTENTIAL FOR IMPROVING GLOBAL MARINE GRAVITY FROM CRYOSAT AND JASON-1

摘要

Marine gravity anomalies derived from radar altimeterrnmeasurements of ocean surface slope are the primaryrndata for investigating global tectonics and seafloorrnbathymetry. The accuracy of the global marine gravityrnfield is limited by the availability of non-repeatrnaltimeter data. Current models, having accuracies of 3-rn5 milligals (e.g., S&S V18 and DNSC08), are based onrnthe non-repeat data collected by Geosat (18 mo.) andrnERS-1 (12 mo.) which use altimeter technology fromrnthe 70’s and 80’s, respectively. The next opportunitiesrnfor significant improvements in marine gravity willrncome from Cryosat and perhaps Jason-1 if it is placedrninto a non-repeat orbit. In addition to complete oceanrncoverage, the three attributes needed for improvedrngravity are improved range precision, optimal satelliterninclination, and long mission duration. We will usernthese methods to assess the range precisions of Cryosatrnand Jason-1 in relation to Geosat, ERS, Topex, andrnEnvisat. We expect that the higher PRF’s of the newerrnaltimeters will provide a square root of 2 improvementrnin range precision. The low inclination of the Jason-1rnorbit offers the best opportunity for improvement in thernE-W variations in gravity, especially at low latitude.rnThe hopefully, long mission duration of Cryosatrnprovides the best opportunity for reducing the noise duernto ocean surface roughness from swells. Data fromrnthese two missions may eventually result in a factor ofrntwo improvement in the accuracy of the marine gravityrnfield and geoid at scales less than 100 km.