Originally Posted by
3wheels
Assuming it is full ATC (you say Tower and you say you were asked to join left downwind) then I would assume he was clearing you to join downwind for a left hand circuit whilst a right hand circuit was generally in use. There could be many reasons for this, the most obvious being that you were approaching from that direction. It’s not at all unusual, so just read back...”Roger G-xxxx to join left hand downwind”. He will soon correct you if it’s wrong.
I’d agree with this. Normally, they do right turns, but for whatever reason, the ATC needed you to do a left pattern. Quite common at busy training airports in the US.