The Study Of Merging Sea Level Anomalies Data Derived From Multi-satellite Altimeter

The sea level anomalies(SLA), which are computed from the difference of the instantaneous sea surface height(SSH) and a mean surface height(MSS), are extensively used for studying the ocean dynamics. Relied on the advantages of large scale, all-time and all weather, satellite altimeter regular monitor sea level and ocean circulation variations and has provided a reliable and simple mean for the acquisition of global SLA data. The multi-mission merged data sets can greatly improve the spatial resolution and the estimation precision of surface height variations, and provide data support for ocean mesoscale dynamics. In our paper, based on the combined use of multi-satellite altimeter are in orbit, these altimeter data are merged into a homogeneous gridded SLA products.Based on the combined use of four multi-satellite altimeter data which include ENVISAT, Jason-1, Jason-2 and HY-2, these altimeter data are analyzed and validated cycle by cycle to eliminate the exceptional data cycle after data editing and geophysical correcting, and the SLA obtained by different altimeter are computed through some concrete calibration models and correction parameters. After that the orbit error reduction is based on a global minimization of dual-crossover and self-crossover differences using the Jason-2 altimeter as a reference, smoothing cubic-spline functions are then used to obtain a continuous estimation of the orbit error over time for ENVISAT, Jason-1 and HY-2 separately. The results show that after the orbit error reduction the differences of dual-crossover and self-crossover are significantly reduced. Then the homogeneous and similar precision global along track SLA products are generated. Based on these data and under the processing of objective analysis method, the global uniform space distribution, time and space resolution of(1/4) ° and 7 days, and regular merged SLA products are generated.Compared with AVISO merged SLA products in global scope and China surrounding seas separately, our merged SLA products show the sea surface variation consistency in corresponding time and the RMS of SLA differences is 3-4cm. The comparison shows the merged SLA products in our paper are accuracy and reliability. Finally, based on the gridded SLA data, the mesoscale eddy detection in global and China surrounding seas are carried out for examining the application ability of merged SLA products.