Aridity - Aridity defines a desert, not temperature. Our average in Davis is about 480 mm. Think back to the Bernoulli Effect. The lift force has to overcome gravity, but it also depends on the difference in density between the fluid and the grains. The lower the density of the fluid, the harder it is to lift the grains against gravity.
Larger grains can only roll along the ground.
The traction and saltation transport are slightly different, however, because the impacts between grains are more forceful. Water dampens the impacts by limiting grain speed by friction between the water and grains and the effects of viscosity. Air does much less so because of both lower density and much lower viscosity. Thus, impacts when saltating grains land are very forceful. This leads to a positive feedback - once saltation starts, the number of saltating grains increases rapidly.