Remote Sensing of Boundary Layer Structure and Height - Wind Energy Meteorology: Atmospheric Physics for Wind Power Generation - page 181

B.3.2 Further Algorithms Using a RASS
Hennemuth and Kirtzel ( 2008 ) have recently developed a method that uses data
from a SODAR-RASS and surface heat flux data. MLH is primarily detected from
the acoustic backscatter intensity received by the SODAR part of the SODAR-
RASS and verified from the temperature profile obtained from the RASS part of
the instrument. Surface heat flux data and statistical evaluations complement this
rather complicated scheme. The surface heat flux is used to identify situations with
unstable stratification. In this respect this observable takes over an analogous role
as the r w in the EARE algorithm ( Sect. B.1.4 ). The results have been tested against
radiosonde soundings. The coincidence was good in most cases except for a very
low MLH at or even below the first range gate of the SODAR and the RASS.
B.4 Other Algorithms Using More Than One Instrument
Using more than one instrument for sounding can help to overcome some of the
above described deficiencies (limited vertical range, limited data availability) of
the individual instruments. Possible combinations are listed in the two following
sections.
B.4.1 Combined Deployment of SODAR and Wind Profiler
Beyrich and Görsdorf ( 1995 ) have reported on the simultaneous usage of a
SODAR and a wind profiler for the determination of MLH. For the SODAR data
the ARE method was used. From the wind profiler data MLH was likewise
determined from the height of the elevated signal intensity maximum (see also
Angevine et al. 1994 ; Grimsdell and Angevine 1998 ; White et al. 1999 ). Good
agreement between both algorithms was found for evolving convective boundary
layers. The vertical ranges of the two instruments (50-800 m for the SODAR and
200-3,000 m for the wind profiler) allowed following the complete diurnal cycle
of MLH.
B.4.2 Combined Deployment of SODAR and Ceilometer
There is an interesting difference between the schemes for the determination of
MLH from acoustic and optical backscatter intensities which should be noted
carefully. While the acoustic backscatter intensity itself is taken for the detection
of H1 and H3 and the first derivative of this backscatter intensity for the
determination of H2 (see Sect. B.1.4 ), the first and the second derivative of the