Using typical sets of numerical parameters under characteristic laser beam propagation conditions, focused beam spreading induced by atmospheric turbulence and thermal blooming is analyzed by numerical simulation. In the analysis of the combined effect, we assume that the thermal blooming effect arises in consequence of the increase in beam radius induced by atmospheric turbulence and beam jitter. The scaling relations between the laser propagation effects and characteristic parameters describing the propagation in atmosphere are obtained. Based upon these relations, we can efficiently estimate atmospheric propagation effects and learn the performance of a particular system design under various environmental conditions, as well as conduct laser system design optimization.