Coherence and Scale of Vertical Velocity in the Convective Boundary Layer from a Doppler Lidar
- 334 Downloads
We utilized a Doppler lidar to measure integral scale and coherence of vertical velocity w in the daytime convective boundary layer (CBL). The high resolution 2 μm wavelength Doppler lidar developed by the NOAA Environmental Technology Laboratory was used to detect the mean radial velocity of aerosol particles. It operated continuously in the zenith-pointing mode for several days in the summer 1996 during the “Lidars in Flat Terrain” experiment over level farmland in central Illinois. We calculated profiles of w integral scales in both the alongwind and vertical directions from about 390 m height to the CBL top. In the middle of the mixed layer we found, from the ratio of the w integral scale in the vertical to that in the horizontal direction, that the w eddies are squashed by a factor of about 0.65 as compared to what would be the case for isotropic turbulence. Furthermore, there is a significant decrease of the vertical integral scale with height. The integral scale profiles and vertical coherence show that vertical velocity fluctuations in the CBL have a predictable anisotropic structure. We found no significant tilt of the thermal structures with height in the middle part of the CBL.
KeywordsCoherence Convective boundary layer Integral scale Lidar Turbulence
Unable to display preview. Download preview PDF.
- Batchelor GK (1953) Homogeneous turbulence. Cambridge University Press, UK, 197 pp.Google Scholar
- Davis KJ (1992) surface fluxes of trace gases derived from convective-layer profiles. University of Colorado, Boulder, COGoogle Scholar
- Frehlich R, Meillier Y, Jensen ML, Balsley B (2006) Measurements of boundary layer profiles in an urban environment. J Appl Meteorol in pressGoogle Scholar
- Kristensen L, Kirkegaard P (1986) Sampling problems with spectral coherence, Technical report Riso-R-526. Riso National Laboratory, DK-4000, Roskilde, DenmarkGoogle Scholar
- Luke YL (1972) Integral of Bessel functions, Handbook of Mathematical Functions Abramowitz M. In: Stegun I. (eds) Dover publications Inc. New York, pp 479–494Google Scholar
- Mayor S, Lenschow DH (2002) Coherence of vertical velocity from a zenith-pointing Doppler lidar. In: 15th Symposium on boundary layers and turbulence, Wageningen, The Netherlands, 15–19 July 2002Google Scholar
- Prueger JH, Kustas WP, Hipps LE, Hatfield JL, Cahill A, Williams CA, Albertson JD, Eichinger WE, Cooper DI, Brunsell N, Gillies R (2003) Spatial variability of turbulent fluxes across a corn/soybean production region in central Iowa’. AMS 17th Conference on Hydrology, Long Beach, CA, USAGoogle Scholar