Earthdata Forum

Hello
I am a researcher who want to use SWOT_SIMULATED_L2_KARIN_SSH_ECCO_LLC4320_SCIENCE_V1 data. However, I find the ssha( I choose the ssha_karin) is very different from the eta of original LLC4320. And I find the ssha(ssha_karin) and ssh(ssh_karin) is the same. I am curious about that question, so i write this letter. Can you explain the reasons? The attached pictures are the same day that I drew using llc4320 and swot simulation. Thanks in advance.

Hello,
My guess is that there is significant cross-swath bias in the simulated dataset. Perhaps this code from the community repository would help (https://github.com/SWOT-community/SWOT-OpenToolkit/blob/main/examples/remove_crossswath_bias.ipynb) If this is the case, then the difference between ssha_karin and ssh_karin should become clearer after cross-swath bias is removed.

Regarding eta versus ssha, I would check the documentation of SWOT (User Handbook and PDD: https://podaac.jpl.nasa.gov/SWOT?tab=datasets-information&sections=about) and any MITgcm documentation about the definitions of ssha and eta, respectively, and compare them.

Hope this helps!

Hello,
thank you for your suggestions, I follow your advise to deal with ssh and ssha with the code(https://github.com/SWOT-community/SWOT-OpenToolkit/blob/main/examples/remove_crossswath_bias.ipynb). However, there are still some problems about the ssh and ssha. The appendices contain the sea surface height (SSH) and sea surface height anomaly (SSHA) piture after I removed the cross-swath bias. However, there are still significant differences between them and the Eta values of LLC4320. I have also attached my code. If there are any errors or areas for improvement, I would greatly appreciate it if you could point them out. Thank you in advance.

Hello,
Sorry to say I'm not able to help any further with science, as I mainly deal with matters of data access and documentation. Perhaps you could ask the ECCO folks https://ecco-group.org/home.htm , or any MITgcm experts, and compare the definitions and reference levels with that of the SWOT SSH products. Is it also worth considering - given that you are comparing 2 snapshots from LLC4320 and SWOT-simulated LLC4320, are they even comparable in absolute values, variance, or area-wide trend? Does the time difference between the simulated ascending passes and descending passes matter, and what is the time range covered by the simulated passes you are looking at?