Yes, ANTITRADES is a Scrabble word!

Letter values in Scrabble US: A 1, N 1, T 1, I 1, T 1, R 1, A 1, D 2, E 1, S 1.

Is it a valid word?

ANTITRADES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

wind in the upper atmosphere blowing above but in the opposite direction from the trade winds
winds blowing from west to east and lying above the trade winds in the tropics

Also: antitrade wind.