[ecco-support] [EXTERNAL] Inquiry Regarding Discontinuities in ADVx_TH and Related Variables in ECCOv4r4 Monthly Tiled Data

[Zhang, Hong (US 398K)]

On May 24, 2025, at 2:25 AM, Qiuhong Liao <qiuhong.liao at student.unsw.edu.au> wrote:

Dear ECCO Support Group,
I hope this message finds you well.
I am writing to seek clarification regarding an issue I encountered while working with the ECCOv4r4 dataset. Specifically, I have been analyzing the ocean heat budget using the monthly tiled data available athttps://ecco.jpl.nasa.gov/drive/files/Version4/Release4/nctiles_monthly.
While processing the variables ADVx_TH, ADVy_TH, DFxE_TH, and DFyE_TH, I noticed significant discontinuities along certain tile boundaries. These discontinuities appear as abrupt changes in the variable values, especially between tiles in regions such as the Pacific and Indian Oceans. For example, ADVx_TH values in these areas are notably higher than those in neighboring tiles, which may adversely impact the accuracy of my heat budget calculations.
<image.png>

I am unsure whether this behavior is an expected feature of the dataset, or if it might be an artifact related to the tiling or reconstruction process. Could you kindly advise on the possible causes and recommend best practices for correctly stitching and interpreting these variables?
Thank you very much for your support and for providing such a valuable resource to the scientific community.
Best regards,
Qiuhong
Hi Qiuhong,
To show vector fields from LLC grid on geographic map, one needs to rotate the vector field.
Your plot of  ADVx_TH is correct for longitude of -38 --142, but wrong elsewhere.
Please check the geometry of LLC grid here
<https://ecco-v4-python-tutorial.readthedocs.io/fields.html#tile-native-lat-lon-cap-90-grid>
ecco-v4-python-tutorial.readthedocs.io<https://ecco-v4-python-tutorial.readthedocs.io/fields.html#tile-native-lat-lon-cap-90-grid>
[X]<https://ecco-v4-python-tutorial.readthedocs.io/fields.html#tile-native-lat-lon-cap-90-grid>

Python code to deal with vector on LLC grid
<https://ecco-v4-python-tutorial.readthedocs.io/ECCO_v4_Interpolating_Fields_to_LatLon_Grid.html>
ecco-v4-python-tutorial.readthedocs.io<https://ecco-v4-python-tutorial.readthedocs.io/ECCO_v4_Interpolating_Fields_to_LatLon_Grid.html>
[X]<https://ecco-v4-python-tutorial.readthedocs.io/ECCO_v4_Interpolating_Fields_to_LatLon_Grid.html>
And matlab one
<https://github.com/MITgcm/gcmfaces/blob/master/gcmfaces_calc/calc_UV_zonmer.m>
gcmfaces/gcmfaces_calc/calc_UV_zonmer.m at master · MITgcm/gcmfaces<https://github.com/MITgcm/gcmfaces/blob/master/gcmfaces_calc/calc_UV_zonmer.m>
github.com<https://github.com/MITgcm/gcmfaces/blob/master/gcmfaces_calc/calc_UV_zonmer.m>
[apple-touch-icon-180x180-a80b8e11abe2.png]<https://github.com/MITgcm/gcmfaces/blob/master/gcmfaces_calc/calc_UV_zonmer.m>

Hope it helps
Hong
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