There is not much information to glean about the relationship between latitude and cloudiness here. It appears as though the two are unrelated with all latitudes showing a wide range of values.
Something which was interesting to me however is that you can see clear horizontal bands in the image. Looking at the data, we find that the vast majority of the points had a multiple of four for the cloudiness percentage. This suggests to me that the data recorded is done so in a discrete fashion rather than continuous, perhaps even by humans rather than machine. I would be interested to see more about how exactly the values are determined.