1. A qualitative term referring to the surroundings of a site, especially to how well its openness will allow in situ measurements made at that site to represent the general area. Exposure is of particular concern for wind, temperature, precipitation, and radiation measurements. See instrument exposure. 2. The amount of time an individual is affected by a particular phenomenon, such as exposure to sunlight as affects UV-induced sunburn, air pollutants, or nuclear radiation. 3. See instrument exposure.