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A simultaneous deployment of Doppler, temperature, and water-vapor lidars is able to provide profiles of molecular destruction rates and turbulent kinetic energy (TKE) dissipation in the convective boundary layer (CBL). Horizontal wind profiles and profiles of vertical wind, temperature, and moisture fluctuations are combined, and transversal temporal autocovariance functions (ACFs) are determined for deriving the dissipation and molecular destruction rates. These are fundamental loss terms in the TKE as well as the potential temperature and mixing ratio variance equations. These ACFs are fitted to their theoretical shapes and coefficients in the inertial subrange. Error bars are estimated by a propagation of noise errors. Sophisticated analyses of the ACFs are performed in order to choose the correct range of lags of the fits for fitting their theoretical shapes in the inertial subrange as well as for minimizing systematic errors due to temporal and spatial averaging and micro- and mesoscale circulations. We demonstrate that we achieve very consistent results of the derived profiles of turbulent variables regardless of whether 1 or 10 s time resolutions are used. We also show that the temporal and spatial length scales of the fluctuations in vertical wind, moisture, and potential temperature are similar with a spatial integral scale of ≈160 m at least in the mixed layer (ML). The profiles of the molecular destruction rates show a maximum in the interfacial layer (IL) and reach values of ϵm≃7×10-4 g 2 kg -2 s -1 for mixing ratio and ϵθ≃1.6×10-3 K 2 s -1 for potential temperature. In contrast, the maximum of the TKE dissipation is reached in the ML and amounts to ≃10-2 m 2 s -3. We also demonstrate that the vertical wind ACF coefficient kw∝w′2‾ and the TKE dissipation ϵ∝w′2‾3/2. For the molecular destruction rates, we show that ϵm∝m′2‾w′2‾1/2 and ϵθ∝θ′2‾w′2‾1/2. These equations can be used for parameterizations of ϵ , ϵm , and ϵθ. All noise error bars are derived by error propagation and are small enough to compare the results with previous observations and large-eddy simulations. The results agree well with previous observations but show more detailed structures in the IL. Consequently, the synergy resulting from this new combination of active remote sensors enables the profiling of turbulent variables such as integral scales, variances, TKE dissipation, and the molecular destruction rates as well as deriving relationships between them. The results can be used for the parameterization of turbulent variables, TKE budget analyses, and the verification of large-eddy simulations. [ABSTRACT FROM AUTHOR]

A simultaneous deployment of Doppler, temperature, and water-vapor lidars is able to provide profiles of molecular destruction rates and turbulent kinetic energy (TKE) dissipation in the convective boundary layer (CBL). Horizontal wind profiles and profiles of vertical wind, temperature, and moisture fluctuations are combined for deriving the dissipation and molecular destruction rates by determining the transversal temporal autocovariance functions (ACFs). These ACFs are fitted to their theoretical shapes and coefficients in the inertial subrange. Error bars are estimated by a propagation of noise errors. 5 Sophisticated analyses of the ACFs are performed in order to choose the correct range of lags of the fits for fitting their theoretical shapes in the inertial subrange as well as for minimizing systematic errors due to temporal and spatial averaging and micro- and mesoscale circulations. We demonstrate that we achieve very consistent results of the derived profiles of turbulent variables regardless whether 1-s or 10-s time resolutions are used. We also show that the temporal and spatial length scales of the fluctuations of vertical wind, moisture, and potential temperature are similar with a spatial integral scale of 10 160m at least in the mixed layer (ML). The profiles of the molecular destruction rates show a maximum in the interfacial layer (IL) and reach values These equations can be used for parameterizations of, m, and l All noise 15 errors bars are derived by error propagation and are small enough to compare the results with previous observations and large eddy simulations. The results agree well with previous observations but show more detailed structures in the IL. Consequently, the synergy resulting from this new combination of active remote sensors enables the profiling of turbulent variables such as integral scales, variances, TKE dissipation, and the molecular destruction rates as well as deriving relationships between them. The results can be used for the parameterization of turbulent variables, TKE budget analyses, and the verification of large eddy 20 simulations. [ABSTRACT FROM AUTHOR]

The light-wind, clear-sky, very stable boundary layer (vSBL) is characterized by large values of bulk Richardson number. The light winds produce weak shear, turbulence, and mixing, and resulting strong temperature gradients near the surface. Here five nights with weak-wind, very stable boundary layers during the Cooperative Atmosphere-Surface Exchange Study (CASES-99) are investigated. Although the winds were light and variable near the surface. Doppler lidar profiles of wind speed often indicated persistent profile shapes and magnitudes for periods of an hour or more, sometimes exhibiting jetlike maxima. The near-surface structure of the boundary layer (BL) on the five nights all showed characteristics typical of the vSBL. These characteristics included a shallow traditional BL only 10-30 m deep with weak intermittent turbulence within the strong surface-based radiation inversion. Above this shallow BL sat a layer of very weak turbulence and negligible turbulent mixing. The focus of this paper is on the effects of this quiescent layer just above the shallow BL, and the impacts of this quiescent layer on turbulent transport and numerical modeling. High-frequency time series of temperature T on a 60-m tower showed that 1) the amplitudes of the T fluctuations were dramatically suppressed at levels above 30 m in contrast to the relatively larger intermittent T fluctuations in the shallow BL below, and 2) the temperature at 40- to 60-m height was nearly constant for several hours, indicating that the very cold air near the surface was not being mixed upward to those levels. The presence of this quiescent layer indicates that the atmosphere above the shallow BL was isolated and detached both from the surface and from the shallow BL. Although some of the nights studied had modestly stronger winds and traveling disturbances (density currents, gravity waves, shear instabilities), these disturbances seemed to pass through the region without having much effect on either the SBL structure or on the atmosphere-surface decoupling. The decoupling suggests that under very stable conditions, the surface-layer lower boundary condition for numerical weather prediction models should act to decouple and isolate the surface from the atmosphere, for example, as a free-slip, thermally insulated layer. A multiday time series of ozone from an air quality campaign in Tennessee, which exhibited nocturnal behavior typical of polluted air, showed the disappearance of ozone on weak low-level jets (LLJ) nights. This behavior is consistent with the two-stratum structure of the vSBL, and with the nearly complete isolation of the surface and the shallow BL from the rest of the atmosphere above, in contrast to cases with stronger LLJs, where such coupling was stronger.

This study combines the experimental measurements with large-eddy simulation (LES) data of a neutral planetary boundary layer (PBL) documented by a 60-m lower instrumented with eight sonic anemometers, and a high-resolution Doppler lidar during the 1999 Cooperative Atmospheric and Surface Exchange Study (CASES-99) experiment. The target of the paper is (i) to investigate the multiscale nature of the turbulent eddies in the surface layer (SL), (ii) to explain the existence of a -1 power law in the velocity fluctuation spectra, and (iii) to investigate the different nature of turbulence in the two sublayers within the SL, which are the eddy surface layer (ESL; lower sublayer of the SL lying between the surface and about 20-m height) and the shear surface layer (SSL; lying between the ESL top and the SL top). The sonic anemometers and Doppler lidar prove to be proper instruments for LES validation, and in particular, the Doppler lidar because of its ability to map near-surface eddies. This study shows the different nature of turbulence in the ESL and the SSL in terms of organized eddies, velocity fluctuation spectra, and second-order moment statistics. If quantitative agreement is found in the SSL between the LES and the measurements, only qualitative similarity is found in the ESL due to the subgrid-scale model, indicating that the LES captures part of the physics of the ESL. The LES helps explain the origin of the -1 power-law spectral subrange evidence in the velocity fluctuation spectra computed in the SL using the CASES-99 dataset: strong interaction between the mean flow and the fluctuating vorticities is found in the SL, and turbulent production is found to be larger than turbulent energy transfer for [k.sub.1]z> 1 ([k.sub.1] being the longitudinal wavenumber and z the height), which is the condition of the -1 power-law existence.

Profiles of mean winds and turbulence were measured by the High Resolution Doppler lidar in the strong-wind stable boundary layer (SBL) with continuous turbulence. The turbulence quantity measured was the variance of the streamwise wind velocity component [[sigma].sup.2.sub.u]. This variance is a component of the turbulence kinetic energy (TKE), and it is shown to be numerically approximately equal to TKE for stable conditions--profiles of [[sigma].sup.2.sub.u] are therefore equivalent to profiles of TKE. Mean-wind profiles showed low-level jet (LLJ) structure for most of the profiles, which represented 10-min averages of mean and fluctuating quantities throughout each of the six nights studied. Heights were normalized by the height of the first LLJ maximum above the surface [Z.sub.X], and the velocity scale used was the speed of the jet [U.sub.X], which is shown to be superior to the friction velocity [u.sub.*] as a velocity scale. The major results were 1) the ratio of the maximum value of the streamwise standard deviation to the LLJ speed [[sigma].sub.u]/[U.sub.X] was found to be 0.05, and 2) the three most common [[sigma].sup.2.sub.u] profile shapes were determined by stability (or Richardson number Ri). The least stable profile shapes had the maximum [[sigma].sup.2.sub.u] at the surface decreasing to a minimum at the height of the LLJ: profiles that were somewhat more stable had constant [[sigma].sup.2.sub.u] through a portion of the subjet layer; and the most stable of the profiles had a maximum of [[sigma].sup.2.sub.u] aloft, although it is important to note that the Ri for even the most stable of the three profile categories averaged less than 0.20. The datasets used in this study were two nights from the Cooperative Atmosphere-Surface Exchange Study 1999 campaign (CASES-99) and four nights from the Larnar Low-Level Jet Project, a wind-energy experiment in southeast Colorado, during September 2003.

Recent observational data (turbulence variables by sonic anemometers and three-dimensional flow pattern by Doppler lidar), obtained during the Cooperative Atmosphere Surface Exchange Study field campaign in October 1999 (CASES-99), show evidence of a layered structure of the near-neutral surface layer: (i) the eddy surface layer (ESL), which is the lower sublayer where blocking of impinging eddies is the dominating mechanism; and (ii) the shear surface layer (SSL), which is an intermediate sublayer, where shear affects the isotropy of turbulence. The origin of the eddies impinging from aloft (probably from the SSL) down to the ESL is preliminarily addressed in this study, since the Doppler lidar data show evidence of linearly organized eddies embedded in the surface layer (i.e., about 100-m vertical extent) and horizontally spaced by about 300 m. This is consistent with theories predicting that the primary mechanism of eddy motion in high Reynolds number wall layers is 'top-down.' The layered structure of the surface layer also has a visible effect on vertical profiles of vertical velocity variance (bar.[w.sup.2]) and momentum transport. In the ESL, (bar.[w.sup.2]) scales as [z.sup.2/3] while it is constant or slightly decreases within the SSL. Concerning momentum transport, ejections contribute identically to the momentum flux as do sweeps in the ESL, whereas in the SSL, ejections give about 50% higher relative contribution.

In the nighttime stable boundary layer (SBL), shear and turbulence are generated in the layer between the maximum of the low-level jet (LLJ) and the earth's surface. Here, it is investigated whether gross properties of the LLJ--its height and speed--could be used to diagnose turbulence intensities in this subjet layer. Data on the height and speed of the LLJ maximum were available at high vertical and temporal resolution using the high-resolution Doppler lidar (HRDL). These data were used to estimate a subjet layer shear, which was computed as the ratio of the speed to the height of the jet maximum, and a jet Richardson number [Ri.sub.j], averaged at 15-min intervals for 10 nights when HRDL LLJ data were available for this study. The shear and [Ri.sub.j] values were compared with turbulence kinetic energy (TKE) values measured near the top of the 60-m tower at the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99) main site. TKE values were small for [Ri.sub.j] greater than 0.4, but as [Ri.sub.j] decreased to less than ~0.4, TKE values increased, indicating that [Ri.sub.j] does have merit in estimating turbulence magnitudes. Another interesting finding was that shear values tended to cluster around a constant value of 0.1 [s.sup.-1] for TKE values that were not too small, that is. for TKE greater than ~0.1 [m.sup.2][s.sup.-2].

This study investigates a shear-flow instability observed in the stably stratified nighttime boundary layer on 6 October 1999 during the Cooperative Atmosphere-Surface Exchange Study (CASES-99) in south-central Kansas. A scanning Doppler lidar captured the spatial structure and evolution of the instability, and high-rate in situ sensors mounted on a nearby 60-m tower provided stability and turbulence data with excellent vertical resolution. Data from these instruments are analyzed and linear stability analysis (LSA) is employed to carefully characterize the wave field, its interaction with the mean flow, and its role in turbulence generation. The event persisted for about 30 min and was confined within the shear zone between the surface and a low-level jet (LLJ) maximum. Eigenvalues corresponding to the fastest growing mode of the LSA showed good agreement with the basic wave parameters determined from the lidar data. Good qualitative agreement was also obtained between the eigenfunction of the fastest growing mode and the vertical profile of the dominant Fourier mode in wave number spectra from spatially resolved lidar data. The height of the measured momentum flux divergence associated with the wave motion was consistent with the LSA prediction of the height of the critical level. Data show that the instability was triggered by an increase in shear due to a slowing of the flow below the LLJ maximum. This low-level slowing produced a local maximum in the shear profile, which was elevated above the surface. The speed and height of the LLJ remained relatively constant before, during, and after the event. Prior to the event turbulent momentum flux increased as the shear increased and as the gradient Richardson number decreased. With the onset of wave activity, a sudden increase in downward wave-momentum flux was accompanied by a sharp reduction in shear near the critical level.

As part of the Land/Sea Breeze Experiment (LASBEX) to study the sea breeze at Monterey Bay, the pulsed Doppler lidar of the NOAA/ERL Wave Propagation Laboratory performed vertical and nearly horizontal scans of the developing sea breeze on 12 days. Analyses of Doppler velocity data from these scans revealed details on the growth of the sea-breeze layer and on the horizontal variability of the sea breeze resulting from inland topography. Two days were selected for study when the ambient flow was offshore, because the onshore flow of the sea breeze was easy to discern from the background flow. Sequences of vertical cross sections taken perpendicular to the coast showed the beginnings of the sea breeze beneath the land breeze at the coast and the subsequent growth of the sea-breeze layer horizontally and vertically. On one of the days a transient precursor - a 'minor sea breeze' - appeared and disappeared before the main sea breeze began in midmorning. Other issues that the lidar was well suited to study were the compensating return flow, the Coriolis effect, the effects of topography, and the growth of the dimensions of the sea-breeze layer. No return flow above the sea breeze and no Coriolis turning of the sea-breeze flow were found even through the late afternoon hours. Terrain effects included an asymmetry in the development of the sea breeze over water as opposed to over land and the persistence into the late morning hours of southeasterly flow from the Salinas River valley toward the vicinity of the lidar. Vertical and horizontal dimensions of the sea-breeze layer were determined from lidar vertical cross sections. From these, length-to-width aspect ratios were calculated, which were then compared with aspect ratios derived from recent analytical models. The theoretical values compared poorly with the observed values, most likely because the complicating effects of topography and stability were not accounted for in the theoretical models.

Author(s): Peter M. Edwards [1, 2, 8]; Steven S. Brown (corresponding author) [1]; James M. Roberts [1]; Ravan Ahmadov [1, 2]; Robert M. Banta [1]; Joost A. deGouw [1, 2]; [...]