A Comparison of Higher-Order Vertical Velocity Moments in the Convective Boundary Layer from Lidar with In Situ Measurements and Large-Eddy Simulation
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We have analyzed measurements of vertical velocity w statistics with the NOAA high resolution Doppler lidar (HRDL) from about 390 m above the surface to the top of the convective boundary layer (CBL) over a relatively flat and uniform agricultural surface during the Lidars-in-Flat-Terrain (LIFT) experiment in 1996. The temporal resolution of the zenith-pointing lidar was about 1 s, and the range-gate resolution about 30 m. Vertical cross-sections of w were used to calculate second- to fourth-moment statistics of w as a function of height throughout most of the CBL. We compare the results with large-eddy simulations (LES) of the CBL and with in situ aircraft measurements. A major cause of the observed case-to-case variability in the vertical profiles of the higher moments is differences in stability. For example, for the most convective cases, the skewness from both LES and observations changes more with height than for cases with more shear, with the observations changing more with stability than the LES. We also found a decrease in skewness, particularly in the upper part of the CBL, with an increase in LES grid resolution.
KeywordsHigher-order moments Lidar measurements Turbulence statistics Velocity moments Vertical velocity
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- Hunt JCR, Kaimal JC, Gaynor JE (1988) Eddy structure in the convective boundary layer—new measurements and new concepts. Q J R Meteorol Soc 482: 827–858Google Scholar
- Militzer JM, Michaelis MC, Semmer SR, Norris KS, Horst TW, Oncley SP, Delany AC, Brock FV (1995) Development of the prototype pamiii/flux-pam surface meteorological station. In: Proceedings of the 9th symposium on meteorological observations and instrumentation. American Meteorological Society, Boston, pp 490–494Google Scholar
- O’Connor EJ, Illingworth AJ, Brooks IM, Westbrook CD, Hogan RJ, Davies F, Brooks BJ (2010) A method for estimating the turbulent kinetic energy dissipation rate from a vertically pointing Doppler lidar, and independent evaluation from balloon-borne in situ measurements. J Atmos Ocean Technol 27: 1652–1664CrossRefGoogle Scholar
- Sullivan PP, Patton EG (2011) The effect of mesh resolution on convective boundary-layer statistics and structures generated by large-eddy simulation. J Atmos Sci (in press)Google Scholar
- Wyngaard J (1988) Structure of the PBL. In: Venkatram A, Wyngaard J (eds) Lectures on air pollution modeling. American Meteorological Society, BostonGoogle Scholar