Issues about geopotential anomaly in Chile

[Lingchao He (River)]

Hi everyone, 

I've acquired SSH, salinity, and temperature datasets from HYCOM via https://ncss.hycom.org/thredds/ncss/GLBv0.08/expt_93.0, covering the period from July 2014 to December 2019 in Chile (-34 -28 -73.5 -71). I've processed the salinity and temperature data to compute geopotential anomaly pressure for comparison against the SSH pressure time series. The results align with expectations, except for anomalies encountered in 2017 and 2019.

Specifically, towards the end of 2017, the geopotential anomaly pressure values are significantly higher than expected. In 2019, there's a clear discrepancy between the SSH pressure data and the geopotential anomaly pressure, with the two datasets not aligning as anticipated. These discrepancies are hindering my progression to further analysis.

I have utilized the same processing approach for all data points. However, I'm uncertain whether these anomalies are attributable to issues with the HYCOM data or potential errors in my processing code or this is not a data issue. I put my result here. Hope someone can help me with this. Thanks in advance! 

Best, 

River

[Rodrigo Duran]

I wouldn't worry too much about the 2017 one, it seems to be a single point, and although it could be something important that warrants attention, errors at a single point in time or space are often an issue that can be ignored. 

The 2019 part of it is more worrying, could it be that HyCOM is correcting SSH from satellite altimetry and therefore the T,S version of it does not agree? Could it be that HyCOM started including atmospheric pressure in 2019? It would be good to know!

Rodrigo. 

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[Lingchao He]

Hi everyone, 

Thanks for many suggestions! I just fixed the problem I asked above. It turns out it's a data downloading issue. However, there are two high-frequency spikes (shorter than 100 days) in the bottom pressure data in March to May 2016 and Nov to Dec 2017 . A study shows there is a northward geostrophic current in the southwest of my studied area in 2016 March to May. The timing is perfect to march with my spike in 2016 but I did not find anything related to 2017 one ( except for La Niña). Could these spikes be artificial errors? Or are they related to ENSO or La Niña or any other short-term processes? And how to test the idea? Any ideas are welcome. Thank you very much!

Best,

River

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Lingchao He(she/her)

PhD Student

University of Rhode Island

Graduate School of Oceanography