Question

what is the rain shadow area beyond the highlands of brazil called ?

Answer 1

Rain shadows are, as Wikipedia puts it, regions on the “leeward side of a mountainous area (away from the wind). The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them”[1].

Brazil doesn’t have a lot of tall mountains, however, and, after doing a bit of googling, I’ve only managed to find one website mentioning areas in Brazil that could be considered to be affected significantly by this phenomenon. According to it, some parts of the Caatinga, an ecoregion typical of the Brazilian Northeast, fall under rain shadow.

If this is true, then there are pockets of rain shadow in the states of Ceará, Piauí, Paraíba, Rio Grande do Norte, Pernambuco, Alagoas, and Sergipe.