At which latitudes do currents of dry sinking air cause the dry conditions of earth's major deserts

Currents of dry sinking air cause the dry conditions of earth's major deserts at: 30° N and 30° S Latitudes

At approximately 30 degrees from the equator, the air that moved up from the equator started to descends. This air, however, could only come from one direction. So when the air is blocked by a mountain, the other side will not receive any water that it contains. This makes the other sides of the mountain became really dry which will eventually cause the formation of the desert.