ISO 28902-1:2012 pdf free download – Air quality – – Environmental meteorology一 Part 1: Ground-based remote sensing of visual range by lidar.
This part of ISO 28902 describes the determination of the visual range via backscattering atmospheric lidar (“Light Detection And Ranging”). Lidars have proven to be valuable systems for remote sensing of atmospheric pollutants, of various meteorological parameters such as wind velocity and direction, cloud and aerosol distribution and composition, shape of the particles, gas concentration, and of optical properties of the atmosphere like extinction and backscatter. A specific feature of lidar methods is their ability to allow spatially resolved remote sensing. The measurements can be carried out without direct contact and in any direction as electromagnetic radiation is used for sensing. Lidar systems, therefore, supplement conventional measurement technology. They are suitable for a large number of tasks that cannot be adequately performed by using in-situ or point measurement methods.
3.14
effective range resolution
application-related variable describing an integrated range interval for which the target variable is delivered with a defined uncertainty
EXAMPLE The range resolution of consecutive extinction coefficient profiles or calculated values of the meteorological optical range (MOR) or vertical optical range (VOR).
3.15
fog
reduction of visibility caused by hydrometeors at a meteorological optical range VMOR < 1 km and relative humidity near 100 % 3.16 mist reduction of visibility caused by hydrometeors with a relative humidity  80 % or dew point differences 3 K for a meteorological optical range VMOR1 km [WMO, 1992[1]; WMO, 200312]; WMO, 2008[6]] NOTE 1 The definition of an upper limit of 5 km is given by ICAOI3I. NOTE 2 National regulations specify differing upper limits due to different definitions of clear sky (e.g. Germany 8 km, Canada 6 miles). 3.17 haze reduction of visibility caused by lithometeors with a relative humidity < 80 % or dew point differences> 3 K for a meteorological optical range VMOR  1 km
[WMO, 1992[1]; WMO, 200312], WMO, 2008161]
NOTE 1 The definition of an upper limit of 5 km is given by ICAOI3].
NOTE 2 National regulations specify differing upper limits due to different definitions of clear sky (e.g. Germany 8 km, Canada 6 miles).
5.2.5 Visual-range determination with lidar
Koschmieder’s theory assumes visible light. However, lidar methods for visual-range determination operate from the near UV region up to the near IR region, at wavelengths from 315 nm up to 1 600 nm 2).
The application of Koschmieder’s theory to lidar methods is possible if wavelength-independent scattering is assumed. This condition can be met in different meteorological situations if backscatter particles are homogenous in shape and diameter (e.g. fog and mist or haze). If instead, there are particle mixtures or inhomogeneities, different theories have to be applied because wavelength independency is no longer a given.
According to Koschmieder’s theory, the application of this part of ISO 28902 is therefore restricted by convention to VMOR  2 000 m3). This meteorological optical range covers the applications described in 8.3. Examples for applications for VMOR> 2 000 m are given in Annex C.
The range-resolved measurement of the extinction coefficient a with lidar allows the meteorological optical range to be determined even in inhomogeneous stratification conditions. This is the essential difference with 5.2.2 and an advantage of visual-range determination with lidar compared to in-situ methods or point measurement methods or observers.