Application of a long range transmissometer to measure the ambient atmospheric extinction coefficient in remote pristine environments

Molenar, John; Dietrich, David; Tree, Roger; Malm, William; Persha, Gerald

From official abstract: "Measurement of the ambient atmospheric extinction coefficient is an essential component of any comprehensive visual air quality monitoring program. The ability to determine extinction in remote pristine Class I areas is difficult due to the need for systems that have 1 ow power consumption, require infrequent servicing, can operate at extreme ambient temperatures, have minimal environmental impact due to sheltering, and can accurately measure near Rayleigh extinctions. In the past extinction has been estimated from nephelometry or natural target contrast measurements with both techniques subject to severe limitations. These operational requirements and instrument limitations have recently been addressed in federal visibility monitoring programs by the implementation of a network of twenty-one Optec LPV-2 transmissometers. The performance of these instruments has been evaluated with a two-year pre-operational test period while the systems were procured and deployed. During this stage, siting requirements, shelter and power system design, data logging systems , installation, standard operating, calibration, maintenance and quality assurance procedures, and instrument reliability and performance characteristics have been thoroughly investigated. The quality and quantity of the collected data and observed operational characteristics illustrate the effectiveness of the measurement technique. The experience gained during the pre-operational test period has led to the full implementation of the operational network as of March 1, 1989."