Introduction - Surface Based Remote Sensing of the Atmospheric Boundary Layer - page 7

The investigation and monitoring of the boundary layer, therefore, had to rely on
ground-based remote-sensing techniques. SODAR and RADAR are able to detect
wind profiles and precipitation; LIDAR instruments basically give backscatter pro-
files. But the near-surface experiments (Wangara and Kansas, see above) had shown
that temperature and humidity profiles are important as well. This finally led to the
development of radio-acoustic sounding systems (RASS) and Raman-LIDAR sys-
tems. RASS determines vertical profiles of the speed of sound and from this the
vertical temperature profile. The first attempts with such an instrument were made
in 1972 (Marshall et al. 1972 ). First humidity profiling was made in 1970 with a
Raman-LIDAR (Cooney 1970 ).
A first review of ground-based remote-sensing techniques for probing the clear
atmosphere has been given by Derr and Little ( 1970 ); the further development of the
sensor technology between 1970 and 1995 with special attention of the atmospheric
boundary layer is described in Wilczak et al. ( 1996 ). The present state of ground-
based remote-sensing instrumentation is summarized in Chapter 3 .
1.4 The Scope of This Topic
This topic will concentrate on ground-based remote sensing of the atmospheric
boundary layer, which has become a major tool for experimental meteorology in
the past decades and which has seen considerable development since the last review
by Wilczak et al. ( 1996 ). In situ and satellite observation techniques will only be
addressed if they form an integral part of the presented ground-based remote-sensing
technique.
Chapter 2 will gather some basic information on the vertical structure of atmo-
spheric boundary layer over different surface types. Both major parts of the ABL,
the surface or Prandtl layer and the Ekman layer, are considered. The most important
analytical profile laws for wind and turbulence are given.
Chapter 3 introduces into the presently available instrumentation for ground-
based remote sensing along horizontal and vertical paths in the ABL. The presented
sounding techniques comprise acoustic, optical, and electromagnetic techniques.
Chapter 4 presents examples of knowledge on the vertical structure of different
types of boundary layers, which has been obtained by ground-based remote sensing
in recent years. This comprises mixing layer and boundary layer height as well as
vertical wind, turbulence, temperature, humidity, and aerosol profiles. The analy-
sis of these profiles does give information not only on the vertical structure of the
boundary layer but also on secondary flow and circulation features occurring within
the boundary layer.
The development and use of ground-based remote-sensing techniques still sees
considerable progress. Therefore, a short outlook on possible future developments
of ground-based remote sensing of the boundary layer will be given in Chapter 5 .
Two appendices give a short overview of the series of ISARS conferences,
which are devoted to boundary layer remote sensing and a glossary of special terms
frequently used in remote sensing.