To monitor sub-regional visibility, a more sophisticated nephelometer and aerosol sampler were installed in South Lake Tahoe. Instruments installed on a meteorological tower measure wind speed and direction, temperature and humidity. Nephelometer data and analysis of collected particles are used to calculate visibility. A camera at South Lake Tahoe checks the view to the north. A transmissometer mounted at the Zephyr Cove Lookout monitors the intensity of a light source across the Lake at Bliss State Park.
Light intensity is related to visibility.
John Molenar, with Air Resources Specialists, Inc., correlated the 1981 measurements with current monitoring data to determine how visibility has changed over the past two decades. And the results are intriguing. For example, there s been a decrease in particle concentrations at South Lake Tahoe since 1981, but the current station is at a different location, so the observation can t be quantified exactly. There s a significant decrease in atmospheric lead concentrations, probably due to phasing lead out of gasoline. Aerosol concentrations at Bliss are greatest in summer.