Winstanley J V, Adams M J
Appl Opt. 1975 Sep 1;14(9):2151-7. doi: 10.1364/AO.14.002151.
A new instrument for the measurement of atmospheric extinction coefficient-the Point Visibility Meter (PVM)-is introduced and its principle of operation discussed. The instrument measures the amount of light scattered at a particular forward scattering angle by haze or fog; the extinction coefficient sigma is then found from the empirical law relating sigma to the scatter at this angle. Detailed calculations of aerosol scattering properties using Mie theory are given to support this empirical law. Error estimates based on these calculations indicate rms errors of less than +/-12% for a range of sigma values 2-60 km(-1). Field trials of the instrument against standard transmissometers confirm these theoretical findings and show a linearity of instrumental output with extinction coefficient, with an rms error of +/-11.7%.
介绍了一种用于测量大气消光系数的新仪器——点式能见度仪（PVM），并讨论了其工作原理。该仪器测量由薄雾或浓雾在特定前向散射角处散射的光量；然后根据将消光系数σ与此角度处的散射相关联的经验定律求出消光系数σ。给出了使用米氏理论对气溶胶散射特性的详细计算，以支持该经验定律。基于这些计算的误差估计表明，对于2-60 km⁻¹范围内的一系列σ值，均方根误差小于±12%。该仪器与标准透射仪的现场试验证实了这些理论结果，并表明仪器输出与消光系数呈线性关系，均方根误差为±11.7%。
