Winds are primarily due to the uneven heating of the planet. The trade winds are due to the circulation of air at the equator up and over to about 30 deg. north, where it sinks and flows back towards the equator. The coriolis effect causes the air to move towards the west. The westerlies rise at 60 degrees north, head toward 30 deg south and then move back towards 60 north. The coriolis effect moves these towards the east. Polar air rises at 60 deg north and sinks at the north pole.