Applications - Surface Based Remote Sensing of the Atmospheric Boundary Layer - page 101

Fig. 4.17 Mean monthly nocturnal wind profile over a town (Hannover, Germany) for August
2002 from SODAR measurements. Also shown are analytical profiles from the first equation in
(2.27) ( thin full line ) and from the complete equation (2.27) ( dotted line )
part of the light spectrum, has a first range gate of data at ~200 m range, a range res-
olution of 30 m, and a velocity precision evaluated at ~20 cm s − 1 (Wulfmeyer et al.
2000 ; Grund et al. 2001 ). Wind-energy-related measurements were, e.g. taken in
the U.S. Great Plains, where a major contribution to the wind resource is a recurrent
nocturnal southerly low-level jet (LLJ) that is prevalent during the warm season.
Important properties of the LLJ are its speed and height, the speed and shear across
the height interval spanned by the rotors, and the magnitude and frequency of tur-
bulence in the rotor layer. These properties were investigated using HRDL at two
locations, southeast Kansas during the Cooperative Atmosphere-Surface Exchange
Study campaign of October 1999 (CASES-99: Banta et al. 2002 ; Poulos et al. 2002 )
and in southeast Colorado, south of the town of Lamar, during the Lamar Low-Level
Jet Project (Kelley et al. 2004 , 2005 ; Pichugina et al. 2004 , 2005a ) in September
2003 (LLLJP-03). In the months immediately following the Lamar deployment,
more than 100 wind turbines were installed at the site of LLLJP-03.
Mean wind profiles were determined using azimuth (conical) scans and elevation
scans (which produce a vertical slice of data in the atmosphere and which were
generally performed parallel to the wind direction) in the abovementioned studies.
Frequency distributions of mean wind properties (speed, direction) are useful for
site assessment of wind-energy potential (Banta et al. 2002 ; Pichugina et al. 2004 ,
2005a ). Another property of the wind profile is the power-law exponent often used
to extrapolate wind-profile data to altitudes above which measurements were taken.
Distributions of this quantity determined by Pichugina et al. ( 2004 )fromHRDL