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southwest of Moscow and the mast at the Boulder Atmospheric Observatory in
Colorado have a height of 300 m), which is by far not sufficient to monitor the
full depth of the boundary layer. The only observation technique that can fill this
gap is remote sensing.
Ground-based remote sensing started with the construction of the first RADAR
devices. Originally developed for military purposes, first meteorological observa-
tions of moving rain bands were made in 1946 by R. Wexler and D.M. Swingle
(Wexler and Swingle 1946 ). In the same year, the first acoustic remote-sensing
devices, SODARs, were constructed by G.W. Gilman, H.B. Coxhead, and F.H.
Willis (Gilman et al. 1946 ) and employed for the analysis of the vertical struc-
ture of the boundary layer. Only the backscatter intensity was recorded from
the first RADAR and SODAR measurements (see, e.g. McAllister et al. ( 1969 )
for the description of the advantages of facsimile plots from acoustic sounding
for the analysis of the vertical structure of the lower atmosphere). Computing
resources for the analysis of the Doppler shift in order to detect wind speeds
were missing at that time. The first Doppler RADAR was operated in 1957
(Brantley and Barczys 1957 ). In acoustic sounding, Doppler analysis to derive wind
speeds was used from 1964 onwards (Kelton and Bricout 1964 , Mahoney et al.
1973 ).
The next push came from the emerging laser techniques. Thus, in 1963, the first
LIDARs (initially called optical RADAR) were used for meteorological observa-
tions (Fiocco and Smullin 1963 ). By 1970, scientists and engineers had conceived
many LIDAR techniques and were building systems to demonstrate and apply
this technology. LIDAR ceilometry (cloud-base height measurement) and obser-
vations of vertical aerosol structure, including inference of the inversion height,
had both been well demonstrated. LIDAR observations of smokestack plume
rise and of transport and dispersion of a cloud of aircraft-sprayed insecticide
had also been performed. A differential absorption of light (DIAL) measure-
ment of the vertical profile of water vapour was reported as early as 1964 (for
a first review on DIAL, see Schotland 1974 ). Wind measurements achieved by
tracking puffs of aerosol particles had been demonstrated, and Doppler measure-
ments of wind motions were just beginning. However, practical applications of
LIDAR were hampered by several difficulties, including fickle lasers, inadequate
data systems, and eye safety restrictions. Experimenters were also encountering
a number of problems, such as inadequate laser frequency control, interferences
from other atmospheric constituents, and gaps in the theory of optical interac-
tion with the atmosphere, all of which required solution before certain atmo-
spheric parameters could be retrieved accurately and dependably (Wilczak et al.
1996 ).
The development of remote-sensing techniques was fostered by the appear-
ance of the first satellites in space. Already 3 years after the first Russian satellite
“Sputnik”, the first meteorological satellite TIROS was launched in 1960. Space-
borne remote sensing, which employs optical or electromagnetic waves, has a
limited vertical resolution, which is not sufficient for detailed boundary layer
studies.
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