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A new in situ measurement system and lidar processing algorithms were developed for improved measurements of boundary layer profiles. The first comparisons of simultaneous Doppler lidar–derived profiles of the key turbulence statistics of the two orthogonal horizontal velocity components (longitudinal and transverse) are presented. The instrument requirements for accurate observations of stably stratified turbulence were determined. A region of stably stratified low turbulence with constant gradients of temperature and velocity was observed above the nocturnal boundary layer using high-rate sensors. The important turbulence parameters were estimated, and turbulence spectra were consistent with new theoretical descriptions of stratified turbulence. The impact of removing the larger-scale velocity features in Doppler lidar estimates of turbulent velocity variance and length scales was investigated. The Doppler lidar–derived estimates of energy dissipation rate ε were found to be insensitive to spatial filtering of the large-scale atmospheric processes. The in situ and lidar-derived profiles were compared for the stable boundary layer in a suburban environment.

Boundary layer profiles of mean temperature, velocity, and small-scale turbulence from in situ sensors, Doppler lidar, sodar, and rawinsondes are intercompared for an urban environment. A new Doppler lidar algorithm is presented to produce high-resolution profiles of small-scale velocity statistics. The lidar-derived profiles are robust and accurate even for challenging conditions such as stable boundary layers with a low-level jet, low turbulence, and low wind speed. Similar results are expected for other locations and convective conditions.

The probability density function (PDF) and spatial statistics of both the energy dissipation rate ϵ and the temperature structure constant C2T are determined for the shear region of a nocturnal jet. The PDF of ϵ and C2T are approximately lognormal. In addition, the joint probability density function of ϵ and C2T is approximately a joint lognormal distribution. The one-dimensional spatial spectra of ϵ and C2T in the inertial region have a k−0.5 and k−0.6 dependence, respectively, where k is the horizontal spatial wavenumber.

Using the unprecedented observational facilities deployed duringthe 1999 Cooperative Atmosphere-Surface Exchange Study (CASES-99),we found three distinct turbulent events on the night of 18October 1999. These events resulted from a density current,solitary wave, and internal gravity wave, respectively. Our studyfocuses on the turbulence intermittency generated by the solitarywave and internal gravity wave, and intermittent turbulenceepisodes associated with pressure change and wind direction shiftsadjacent to the ground. Both the solitary and internal gravitywaves propagated horizontally and downward. During the passage ofboth the solitary and internal gravity waves, local thermal andshear instabilities were generated as cold air was pushed abovewarm air and wind gusts reached to the ground. These thermal andshear instabilities triggered turbulent mixing events. Inaddition, strong vertical acceleration associated with thesolitary wave led to large non-hydrostatic pressure perturbationsthat were positively correlated with temperature. The directionaldifference between the propagation of the internal gravity waveand the ambient flow led to lateral rolls. These episodic studiesdemonstrate that non-local disturbances are responsible for localthermal and shear instabilities, leading to intermittentturbulence in nocturnal boundary layers. The origin of thesenon-local disturbances needs to be understood to improve mesoscalenumerical model performance.

Finescale temperature and velocity measurements with multiple vertically spaced cold-wire and hot-wire sensors on the Cooperative Institute for Research in the Environmental Sciences (CIRES) tethered lifting system (TLS) were produced during the Cooperative Atmosphere–Surface Exchange Study-1999 (CASES-99). The various calibration methods are presented as well as algorithms to extract high-resolution estimates of the energy dissipation rate ϵ and the temperature structure constant C2T. The instrumentation is capable of measurements of ϵ ≈ 10−7 m2 s−3 and C2T ≈ 10−6 K2 m−2/3.

During the Cooperative Atmosphere‐Surface Exchange Study-1999 (CASES-99) campaign in southeastern Kansas in the fall of 1999, the University of Colorado’s Cooperative Institute for Research in Environmental Sciences (CIRES) made a series of vertical profiling measurements using the CIRES tethered lifting system (TLS). The results reported here began during a period when the nocturnal boundary layer (NBL) was characterized by a low-level jet (LLJ) peaking at 120 m and a temperature profile that increased smoothly with height to a point slightly above the height of the LLJ peak. Then, within a period of less than 30 min, the character of the NBL changed abruptly, with the breakdown of the well-defined LLJ and the appearance of a surprisingly steep temperature change of some 3.5 K around 180‐190 m AGL. Part of this inversion was extremely sharp, with the steepest portion showing a temperature change of 1 K over an altitude range of only 5 cm, corresponding to a vertical temperature gradient in excess of 20 K m 21. The general shape of this steep gradient was maintained—albeit with slightly reduced values—for at least 20 min. It is understood that the magnitude of the steepest portion of this gradient exceeds all previously observed atmospheric gradients by over an order of magnitude, although comparable gradients—albeit under very disparate conditions—have been observed in the ocean. A second surprising feature apparent in these results was the steepness of the gradients in turbulence structure at the top of the NBL and within the residual layer (RL), the region above the NBL that is usually slightly stably stratified and extends upward to the height marked by the vestiges of the previous day’s capping inversion. At the NBL top, energy dissipation rates and temperature structure parameters dropped sharply by more than one order of magnitude over a distance of only a few meters. At higher altitudes within the RL, a 60-m-thick region of very weak turbulence was observed. This low-turbulence region also exhibited sharp edges, where energy dissipation rates and temperature structure parameters changed by at least an order of magnitude over vertical distances of only a few meters.

Results of the refractive index structure parameter (CT2), Cn2, and the eddy dissipation rate, (epsilon) , derived from the velocity structure parameter, Cv2, are presented from high speed fluctuation measurements taken using a kite/tethered-blimp platform in the Tularosa Basin at White Sands Missile Range, NM during the spring of 1998. Comparisons of different sensor measuring the same parameter are displayed and discussed. Salient features of the sensors and the kite and blimp platforms are outlined. Long term measurements of high speed fluctuations of temperature and velocity are shown and intermittency of turbulence is discussed. The nature and statistics of turbulence inside, outside, and at the boundary of a turbulent layer are also shown and interpreted. Observations in the entrainment zone at the top of the planetary boundary layer are shown and similarities of characteristics found in the tropopause region with these boundary layer features is discussed. The diurnal variation of turbulence is presented with particular emphasis on the transition period from the end of daytime convection to development of the stable nocturnal boundary layer. Results are displayed as profiles and histograms of Cn2 and (epsilon) for daytime, near sunset, and nighttime conditions.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Results of the (temperature) refractive index structure param- eter (CT ), Cn , and the eddy dissipation rate e derived from the velocity structure parameter Cv are presented from fast response sensor obser- vations using a kite/tethered-blimp platform in the Tularosa Basin at White Sands Missile Range, New Mexico, during the spring of 1998. Comparisons of different sensors (fine-wire probes and pitot tubes) mea- suring the same parameter are displayed and discussed while salient features of all sensors (standard and fast response) and the kite and tethered-blimp platforms are outlined. The nature and statistics of turbu- lence, including intermittency, under different stability conditions is dis- cussed, including those found in the residual layer above the nocturnal boundary layer and the entrainment zone at the top of the daytime plan- etary boundary layer. In addition to displaying time series of temperature C n and e results obtained at specific altitudes and times, histograms of all daytime and nighttime Cn and e values are compared to log-normal distributions. Examples of profiles ofC n and e for daytime, near sunset, and nighttime conditions are shown and discussed. The relationship of Cn with e is displayed for all data as well as sorted by daytime and nighttime. These results are explained in terms of potential and kinetic energy considerations under different atmospheric stability conditions. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)03209-8) Subject terms: turbulence; refractive index structure parameter; atmospheric propagation; meteorology; velocity; temperature; sensors.