The Amazon plain has a tropical rainforest climate. Why is there a big seasonal difference in precipitation?

Tropical rain forest climate is a relative concept, that is, it is hot and rainy all year round.

But it doesn't say that it must rain every day every month.

Therefore, the dividing line between different climates is not clear.

Brazil's tropical rain forest, first of all, its rainfall has supported the formation of the local rain forest landscape, so it is not wrong to be classified as a tropical rain forest climate.

However! Around July every year, the equatorial convergence zone is obviously northward, probably in the Caribbean. At this time, the tropical rain forest in Brazil is controlled by the southeast wind, and the subtropical high in the southern hemisphere extends westward in winter, controlling the southern Brazilian plateau. Dry and hot winds blow from the southeast, or the plateau blows to the plain. So around July, the Amazon Plain is dry and hot. Even if the local sun is the lowest at this time, it will be the hottest time of the year in the next 2-3 months.

This is the source of seasonal precipitation difference in local tropical rain forest. This dry and hot weather lasts for 1~2 months every year, and the overall local environment remains unchanged.