The Influence On Accuracy Of Visibility Measurement For The Changes In Wavelength Of Light Source

Visibility has an important impact on transportation, marine, aviation and military files. At the same time, visibility also represents the cleanliness of the atmosphere directly in the atmospheric monitoring field. Atmospheric aerosol as the important factor which affects the visibility is also closely related to human health. Therefore, it has a significant impact on people’s production and life to measure visibility timely and accurately. The changes in wavelength of light source have a great impact on the visibility measurement, so it is necessary to study the influence on visibility measurement for the changes in wavelength of light source.The visibility mainly depends on the measurement of atmospheric extinction coefficient and atmospheric extinction coefficient depends on the measurement of the light transmittance in the method of transmission type. A system was designed to measure the light transmittance, the light transmittance of the400-1100nm waveband was measured after the light passed through the aerosol in the experiment. The relation between aerosol particle size distribution and the change of light transmittance curve state was analyzed based on Mie scattering theory. The accuracy of Koschmieder empirical formula was verified combined with the data measured in the experiment. At the same time the influence of detection wavelength drift on visibility measurement was also analyzed.The results show that the distribution of the transmittance curve is different under the different aerosol concentration. The spectral transmittance depends on the aerosol concentration and the aerosol particle size distribution determines the change of spectral transmittance curve state. There is a large error when using the existing empirical formula to calculate visibility. The correction coefficient of visibility measured by light of different wavelengths in the same environment is different. And the correction coefficient of visibility measured by light of the same wavelength in the different environment is also different. The relative error of visibility measurement increases with the range of detection wavelength drift in linearity. With the increasing range of detection wavelength drift, the rate of the relative error in visibility measurement increases linearly at each wavelength is different. Under the same range of detection wavelength drift, the visibility measurement error is different by using the different detection wavelength.