Applications - Surface Based Remote Sensing of the Atmospheric Boundary Layer - page 88

Fig. 4.6 Comparison of schematics for the MLH determination from SODAR (left-hand graph)
and ceilometer (middle and right graphs). The right-hand graph shows the vertical derivative of the
middle graph. Therefore, the left-hand graph and the negative of the right-hand graph have many
similarities

rather high attenuation of sound waves in the atmosphere. In contrast, optical remote
sensing offers much larger height ranges of at least several kilometres, because the
attenuation of light waves in the atmosphere is small unless there is fog, clouds, or
heavy precipitation. The analysis of the SODAR data and the ceilometer data can be
combined to one single piece of MLH information by forming the minimum from
( 4.4 ) and ( 4.11 ):

MLH = min(MLH ac ,MLH op ), (4.13)

4.2.1.5 Correlation of Pollutant Concentrations with MLH

This subsection is to give examples for the application of continuous mixing layer
depth information from ground-based remote sensing.
Concentration of pollutants which are emitted at or formed near the surface
should correlate with MLH, because the depth of the mixing layer defines the
size of the atmospheric volume in which these pollutants can dilute. This corre-
lation should be best for aged inert substances away from their direct sources that
have already efficiently been mixed in the vertical. For the investigation of these
correlations, the influence of horizontal advection should be negligible, either due