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Global valid observations of ocean color products

Posted: Sat May 13, 2023 4:10 am America/New_York
by hzk15
Recently, I have been working with ocean color product data and downloaded MODIS-T/A and VIIRS-NPP Chl-a data from the website, with a daily-temporal and 4km-spatial resolution.
Due to factors such as cloud cover and sun glint, the Chl-a satellite-based data is severely affected by missing values. Therefore, I conducted a statistical analysis on the global valid observations of these three products and found that stripe patterns appeared in mid-latitudes and low latitudes of both hemispheres (referring to the attachment), which I consider to be potentially unreasonable. Moreover, I obtained similar results when using GEE for computation.
May I ask whether this is a problem with the product itself, or whether there are other reasons that can explain the occurrence of similar phenomena?

Re: Global valid observations of ocean color products

Posted: Wed May 24, 2023 4:04 pm America/New_York
by OB General Science - guoqingw

The pattern doesn't make sense to me, and this shouldn't be a problem with the products. But just in case, can you please provide more details about what you did? Did you use the whole dataset (all the available l3 Chlorophyll products) for each mission to calculate the ratio? Is the ratio calculated using a function similar to: valid_pixels/total_pixels over the years for each lat/lon?