The South Equatorial Belt (SEB) in 2021 was essentially the same as in the previous two years, so this report focuses mainly on the Great Red Spot (GRS) and the structures around it, which have attracted attention for the last few years.  By now it is apparent that the remarkable changes in the GRS in 2019, and the further changes in 2021, result from three concurrent processes:

i) Short term: Impacts of incoming SEBs rings, which sometimes strip reddish flakes from the GRS.  Many SEBs rings were arriving in 2021, but we report that their effects on the GRS were mostly rather minor, as in 2020, with only a few examples of flakes.

ii) Medium term: The Hook and S.Tropical Band (STropB).  These occur together, at irregular intervals, on average once per 2 years or so, and last for some months.  Dark material from the Hook appears to flow around the S rim of the GRS and into the STropB.  A substantial Hook with STropB was present from 2021 Feb. up to July.

iii) Long term:  Shrinkage of the GRS, which has been ongoing for at least a century.  In 2021 it again had the smallest size ever recorded, with a mean length of 12.3 deg. 

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The text of the report is here:   Report-no-8_GRS-2021.pdf

Miniature copies of Figures 1-7 are here:  Report-no-8_GRS-2021_Minifigs.pdf

All the full-size figures are here:    Report-no-8_GRS&SEB_Figures.zip

Appendix 1 (all by S. Mizumoto):  Three reports on the Hook and the associated deviations of spots across the STropZ f. and p. the GRS;  & two animations of maps (one of which is shown below).   Report-no-8_GTRS&SEB_Appendix.zip