Atmospheric Turbidity Across the Los Angeles Basin

Abstract

Atmospheric turbidity (aerosol optical thickness) was measured with sunphotometers across the Los Angeles Basin. Automobiles were used for east-west traverses of the metropolitan area (a distance of ?100 km) on two days with distinctly different meteorological conditions: a hazy, relatively humid day and a warmer, dryer, less hazy day with easterly Santa Ana wind flow. Additionally, incident global UV and total solar irradiance were measured at six sites (five urban and one rural) and nephelometer measurements of aerosol concentrations were made at two locations. On the hazy day turbidity was remarkably uniform across the Los Angeles Basin. In contrast, significant variation of turbidity from west to east occurred on the less polluted day. Solar radiation measurements also reflected the day-to-day and spatial turbidity differences. During the hazy day the urban sites received only 64?76% as much UV energy as did the rural mountain site. With easterly Santa Ana wind flow, San Bernardino received 17% more total solar energy than on the hazy day.