Weird signal pattern observed in GOMex experiment

[Siddhesh Tirodkar]

Hi,

 

Greetings for the day.

 

I am Siddhesh Tirodkar, postdoctoral fellow at Florida Atlantic University.

 

I went through the different set of experiments data available for Gulf of Mexico region for years from 2011 to 2022 (GOMex and GOFS).

 

In GOMex experiments, GOMI0.04 expt_32.5, I have observed the signals of 5- and 17-days frequency in ssh, u and v current for year 2017, 2018 (u and v plots are not shown). Find attached figure 1 for reference. The figure 1 shows the ssh evolution in time at 31 N for 2017-2018. We usually don’t see these signals and they are disturbing our simulations.

 

I tried to check, GOMI0.04 exp_31.0 for year 2011 and 2012, but this experiment does not show these signals. Find attached figure 2 for reference. The figure 2 shows the ssh evolution in time at 31 N for 2011-2012. The model output for this experiment is better.

 

I am not able to identify this variation in the data before year 2014. The 17 days frequency signal in GOMex data GOMI0.04 expt_32.5 ssh has total variation range of 1.6 m (see figure 3) which is much higher than 2011–2012-year ssh variation (refer figure4) of 0.3 m.

 

If we compare the GOMex experiment with GOFS experiments, then it is observed that the GOFS experiments GLBv0.08 does not show such signal of 17-day frequency (refer figure 5). I have observed this issue with GOMex experiment for years after 2014.

 

Any help identifying the source in this regard will be appreciated.

 

If you need any more information, please let me know.

 

-Thanks & Regards,

Siddhesh Tirodkar

Postdoctoral Fellow

Harbor Branch Oceanographic Institute,

Florida Atlantic University

+17869340456

 

[Alan Wallcraft]

The GOFS and GOMI0.04 exp_31.0  cases do not include tides.  I suggest you filter out tides before doing an analysis.  A crude way of doing this is to use 1-day means or a 1 day running mean.

Compare with HYCOM-TSIS 1/25º Gulf of Mexico Reanalysis

This is a more recent product and since it is produced at COAPS we better positioned to provide assistance.  If this does not have the 5- and 17-days frequency signals then the best option is to abandon 32.5.

Alan.

[Siddhesh Tirodkar]

Hi Alan,

 

Thank you for your reply.

 

I will check the HYCOM-TSIS GOMex reanalysis and let you know my findings.

 

-Thanks & Regards,

Siddhesh Tirodkar

Postdoctoral Fellow

Harbor Branch Oceanographic Institute,

Florida Atlantic University

+17869340456

 

From: Alan Wallcraft <alan.wa...@hycom.org>
Sent: Friday, June 14, 2024 12:23 PM
To: HYCOM.org Forum <fo...@hycom.org>
Cc: Siddhesh Tirodkar <stir...@fau.edu>
Subject: Re: Weird signal pattern observed in GOMex experiment

 

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[Siddhesh Tirodkar]

Hi Alan,

 

Greetings of the day.

 

I went through the HYCOM-TSIS GOMex product for 2 different years (2011 & 2017).

 

First, I took the raw data for 60 days for every year and took a transect at 31 N (figure1 and figure4).

I filtered tide from the data for both year by 24-hour averages (figure2 and figure5).

Figure 3 is from GOMI0.04 expt_32.5 for year 2017 and figure 6 is from GOMI0.04 exp_31.0 for year 2011. (these datasets are raw)

 

From figure 1, 2 and 3 for year 2017, I can see that there is still some 15-day frequency peak in HYCOM-TSIS and GOMI0.04 expt_32.5.

If I consider figure 4, 5 and 6 for year 2011, the same frequency peak is absent in GOMI0.04 exp_31.0 but visible in HYCOM-TSIS output.

 

I am not able to understand this frequency visible in data. The similar frequency is also available in barotropic velocity in u and v (figure7). This data alters the inflow into the Gulf of Mexico.

 

Any help in this reference will be useful.

 

-Thanks & Regards,

Siddhesh Tirodkar

Postdoctoral Fellow

Harbor Branch Oceanographic Institute,

Florida Atlantic University

+17869340456