1. In general, expresses the rate of transfer per unit area of some condition or physical quantity, such as rainfall, electromagnetic energy, sound, etc. 2. (Or radiant intensity. ) Radiant power per unit solid angle; in SI units, W sr−1. 3. In synoptic meteorology, the general strength of flow around an individual cyclone or anticyclone (most often applied to the former). This concept is commonly used in terms of a process, “intensification,” or descriptively, as an “intense low. ”