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clarification-this is an example and it is the AOD time serie at a longitudinal segment (AOD VERSUS latitude) in the atlantic next to the africa during 15 years (2000-2014) using the combined dark target and deep blue data. I do not understand the white areas (between 20 and 22°N)that sistematically appear in the AOD field. thank you for answerI have a doubt about the 'white spaces' in the maps from satellite. For example, for the atlantic areas I have plotted AOD and appear many areas where sistematically do not have any data (white spaces). So I want to know why that happens or which factors are behind that.

thank you for your answer

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  • $\begingroup$ What is the source of the image? $\endgroup$
    – f.thorpe ♦
    Oct 6, 2016 at 0:24
  • $\begingroup$ I plotted the images using terra-dark target-550nm product. $\endgroup$
    – Adilson Vladmir C. Veiga
    Oct 6, 2016 at 1:13
  • $\begingroup$ What is this image supposed to show? $\endgroup$
    – Jan Doggen
    Oct 6, 2016 at 8:26
  • $\begingroup$ the image shows time series of the AOD at a longitunal segment in the atlantic next to the africa. $\endgroup$
    – Adilson Vladmir C. Veiga
    Oct 6, 2016 at 20:05

1 Answer 1

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Expect every daily retrieval of AOD to have many missing pixels, mostly where clouds appear. Data is removed when the quality assurance flags do not meet some minimum criteria. This can happen when the retrieval is contaminated (e.g. from clouds or sun glint on the surface). If you are interested, you can obtain raw level-1 and level-2 data with all data, including arrays for quality assurance flags.

There will also be systematic gaps in the data where the satellite had no coverage. Polar orbiting satellites will get complete coverage near the poles, but widening gaps will appear the closer you get to the equator.

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  • $\begingroup$ I thank you for your answer. I uploaded an example (image) that helps understanding the nature of the question. I dont belive that the problem is caused by clouds because during 15 years, there was no record. I am waiting for your helping $\endgroup$
    – Adilson Vladmir C. Veiga
    Oct 6, 2016 at 0:15
  • $\begingroup$ If you are referring to the white stripe above 20 latitude, I don't know what that is. Perhaps this is a longitudinal slice, and that is a water feature? There are different algorithms used for "over land" and "over water" AOD, so depending on the data source, it might not include both. Or, perhaps it's a specific location with very high albedo (e.g. Sahara desert) where an AOD retrieval might have trouble. $\endgroup$
    – f.thorpe ♦
    Oct 6, 2016 at 0:25
  • $\begingroup$ the product is from terra-dark target-550nm and over a segment north-south in the atlantic ocean in the outflow of the african continent. really it is dificult to know the cause, but I believe that is something related to the retrieval $\endgroup$
    – Adilson Vladmir C. Veiga
    Oct 6, 2016 at 0:59
  • $\begingroup$ If it's over ocean, it could be an island or other piece of land. The over-land and over-ocean data are not necessarily in the same dataset. $\endgroup$
    – f.thorpe ♦
    Oct 6, 2016 at 4:49

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