Applications - Surface Based Remote Sensing of the Atmospheric Boundary Layer - page 74

Table 4.1 Overview on methods using ground-based remote sensing for the derivation of the
mixing layer height mentioned in this chapter (see rightmost column for section title)

Method Short description Section

Acoustic ARE Analysis of acoustic

backscatter intensity

Acoustic Received Echo Method

Acoustic HWS Analysis of wind speed

profiles

Horizontal Wind Speed Method

Acoustic VWV Analysis of vertical wind

variance profiles

Vertical Wind Variance Method

Acoustic EARE Analysis of backscatter and

vertical wind variance
profiles

Enhanced Acoustic Received Echo
Method

Optical threshold Detection of a given

backscatter intensity
threshold

Threshold Method

Optical gradient Analysis of backscatter

intensity profiles

Gradient or Derivative Methods

Optical idealized
backscatter

Analysis of backscatter
intensity profiles

Idealized Backscatter Method

Optical wavelet Analysis of backscatter

intensity profiles

Wavelet Method

Optical variance Analysis of backscatter

intensity profiles

Variance Method

Acoustic/electromagnetic RASS RASS

Acoustic/electromagnetic SODAR-RASS and

windprofiler-RASS

Combined Deployment of Two
Different RASS

Acoustic/in situ SODAR-RASS plus surface

heat flux data

Further Algorithms Using a RASS

Acoustic/electromagnetic SODAR plus windprofiler Combined Deployment of SODAR

and Wind Profiler

Acoustic/optical SODAR plus ceilometer Combined Deployment of SODAR

and Ceilometer

A variety of different algorithms have been developed by which the MLH is
derived from ground-based remote-sensing data (see Table 4.1 for a short overview).
We will mainly concentrate on acoustic and optical remote sensing because electro-
magnetic remote sensing has too high lowest range gates for a good coverage of
shallow MLH. The disadvantage of a too high lowest range gate can partly be cir-
cumvented by slantwise profiling or conical scanning if the assumption of horizontal
homogeneity can be made.

4.2.1.1 Acoustic Methods

Acoustic methods either analyze the acoustic backscatter intensity, or, if Doppler
shifts in the backscattered pulses can be analyzed, features of vertical profiles of
the wind components and its variances as well. The acoustic backscatter intensity is
proportional to small-scale fluctuations in atmospheric temperature (usually gener-
ated by turbulence) or by stronger vertical temperature gradients. The latter feature