MODIS Average quality level

[chaeck]

Hi all,

I am looking at trends of SST horizontal gradients and variability, and artefacts in yearly averages have prompted me to look at the SST quality level.

When averaging over a couple of months (I have tried years 2008 and 2020), the quality level (qual_sst4) is showing higher values in a rectangle spanning 105W-105E ; 30N-10S (see attached plot for the year 2008). This is also noticable in the SST variability, for instance the SST standard deviation in a rolling window is higher in the same rectangle.

I am using the L3 daily nighttime SST4 V2019 (https://podaac.jpl.nasa.gov/dataset/MODIS_AQUA_L3_SST_THERMAL_DAILY_4KM_DAYTIME_V2019.0), downloaded with the podaac-data-downloader. I have computed the average with xarray and nces to similar results.
This does not show in the yearly product (https://podaac.jpl.nasa.gov/dataset/MODIS_AQUA_L3_SST_MID-IR_ANNUAL_4KM_NIGHTTIME_V2019.0).

Could that be an expected consequence of the processing? I don't have any clue as to where this could come from.

Thanks,

[PODAAC - edward.m.armstrong]

Hi

Could you check your work and reattach your plot? The one attached does not match the study region of interest.

There might be some small differences in Sea Surface Temperature and quality level between the SST and SST4 MODIS products, but should not be significant.

regards,
Ed Armstrong, JPL PO.DAAC

[chaeck]

Thank you for your response.

What I meant is that there is a sharp increase in average quality level inside that rectangle. Maybe to make it clearer, here is a zoom on the south-east corner.

Erratum: the link in the first post is wrong, I used the Mid-IR / SST4 product. In fact, the issue is not showing on the Thermal-IR / SST product.