The Origin of Haze in the Central United States and Its Effect on Solar Irradiation

Abstract

The depletion by atmospheric haze of solar irradiation at the earth's surface in the central United States is estimated and some aspects of the origin of the haze investigated. Observed optical properties of the haze are reviewed and their relation to visual range measurements demonstrated. An approximate radiative transfer model relates visual range and mixing-height observations to solar irradiance at the ground, and the relation is validated against detailed irradiance observations on two days, and against observed monthly and annual irradiation at one station. Statistics of irradiation depletion are computed for 24 stations. The annual average depletion is ∼7.5%. By means of a simple regional-scale air quality model, it is shown that haze properties and solar radiation depletion can be satisfactorily related to EPA emission inventories for particulate matter and sulfur dioxide.