I'm a Brazilian native. Here, the English translation to the most didactic way to express the Amazon seasons are: "rainy season", and "less rainy season", because it always rains a lot, but there is a period when there is less. Does anyone know if this is the best way to express this in English scientific language?
While not being very descriptive, 'dry season' is in general use, even for rainforests (Af Koppen climate, if you will). Example papers using the terminology here.