Friedrich Köpp

Representativeness of wind measurements with a cw Doppler lidar in the atmospheric boundary layer.

The representativity problem of laser Doppler anemometer wind measurements in the boundary layer under different atmospheric conditions has been investigated theoretically and experimentally. The calculations of the mean wind-velocity measurement errors for the surface layer under different types of thermal stratification and for the boundary layer under neutral conditions have been carried out. The theoretical conclusions are confirmed by the experimental results.

Measurements of Turbulent Energy Dissipation Rate with a CW Doppler Lidar in the Atmospheric Boundary Layer

Abstract The results of a theoretical and experimental study of the feasibility of the turbulent energy dissipation rate ϵT measurements with a continuous wave (CW) CO2 Doppler lidar in the atmospheric boundary layer are presented. Three methods of probing ϵT are considered: 1) Doppler spectrum width, 2) the temporal spectrum (temporal structure function) of wind velocity measured by the Doppler lidar, and 3) spatial structure function. In these methods, information on the dissipation rate is extracted by means of analysis of the corresponding statistical characteristics of wind velocity in the inertial subrange of the turbulence, taking into account the spatial averaging of the measured wind velocity fluctuations over sounded volume. In the first and third methods, the spatial structure of the turbulence is analyzed directly. In the second method, to determine ϵT from the measured temporal characteristics, it is necessary to use a model for the spatiotemporal correlation function of wind velocity. As a r...

Characterization of Aircraft Wake Vortices by Multiple-Lidar Triangulation

Three continuous-wave lidar systems have been deployed to measure simultaneously the aire ow associated with wake vortices generated by a medium-size full-scale test aircraft. The lidar systems were positioned to permit investigation of fundamental aspects of vortex behavior. Two lidars were located 27 m apart, along a line parallel to the glide slope. This allowed a consistency check via comparison of the two sets of results and gave an indication of axial variations in vortex location and character. The third lidar was positioned 80 m away along a line perpendicular to the glide slope. This permitted accurate location of the vortex cores by triangulation methods via a tracking algorithm based on an extended Kalman e lter, typically to an accuracy of better than § §4.0 m. The mean value of core separation for a vortex age of 2 s agrees to within 5% of that predicted for this aircraft using the approximation of elliptically distributed lift. Calculation of vortex circulation requires accurate information on vortex range in conjunction with tangent velocity proe les: The trajectories thus determined are an essential input, and, hence, this method will reduce the uncertainty in the values of circulation in comparison to studies involving only a single lidar.

Influence of clouds and fog on LDA wind measurements.

The influence of clouds and ground fog on CO2 cw laser Doppler wind measurements in the atmosphere is discussed. There is an influence if the focal volume of a laser Doppler anemometer is outside the cloud or fog region. Limitations of the application of the LDA to routine remote wind sensing are presented.

On-line data system for a cw laser Doppler anemometer.

The DFVLR infrared Doppler lidar has been equipped with an on-line data system. It utilizes a peak-finder circuit, a transient recorder, and a microcomputer to evaluate a certain wind quantity from temporal series of measured radial wind components. By means of one example, i.e., the determination of vertical wind profiles in the atmospheric boundary layer, the efficiency of the on-line data system is shown. It takes between 3 and 7 min to derive a profile of wind vectors from the surface up to a 750-m height.

Remote Measurements Of Plume Dispersion Over Sea Surface Using The DFVLR Minilidar

The dispersion of artificial aerosol plumes over sea surfaces was measured using a portable lidar system. The momentary distribution of aerosol concentrations could be derived from short-time measurements. Some effects of the aerosols and the sea surface on the plume dispersion were estimated.

Fernmeßverfahren@@@Remote sensing of mass fluxes of trace gases in the boundary layer mit FTIR-Spektrometrie und Laser Doppler: Messung von Abgasen des Heizkraftwerks München-Nord

ZusammenfassungDie Kombination von Fernerkundungsverfahren wie Fourier-Transform-Infrarot (FTIR)-Spektrometrie und Lidar eröffner die Möglichkeit, Massenflüsse von Gasen zu erfassen. Das Doppler Lidar mißt dabei das dreidimensionale Windfeld und in der Nähe eines Kamins die Änderung des Windfeldes in der Umgebung der Austrittsöffnung. Die Fourier-Transformation des Interferogramms von einem Michelson-Interferometer berechnet aus der aufgezeichneten Intensität (Funktion des Spiegelweges im Interferometer) das spektrale Signal (Spektrum, Funktion der Wellenlänge der Strahlung). Daraus wird durch Analyse der Ausbreitung infraroter Strahlung von der Abgaswolke zum Teleskop des Interferometers die Konzentration der Gaskomponenten bestimmt. Beide Informationen, Geschwindigkeit und Konzentration, ergeben zusammen den Massenfluß des betrachteten Gases. Es wurden die Massenflüsse von CO2, CO, NO und HCl bestimmt, die in guter Übereinstimmung mit den Daten des Kraftwerkes sind. Eine Überwachung von außerhalb des Kraftwerkes ist mit optischen Fernerkundungsverfahren möglich.AbstractThe combination of remote sensing methods like Doppler lidar and FTIR allows remote determination of mass fluxes of gases. Doppler lidar measures the three-dimensional wind vector in the vicinity of diffuse sources, or the velocity of air in a chimney plume if an industrial complex is monitored. FTIR is a multicomponent remote sensing method for gas concentrations. The Fourier transformation of an interferogram of a Michelson interferometer within a FTIR system converts the recorded intensity (function of optical path length) to a spectral signal (function of wavenumber). Both information, velocity and concentration, give the mass fluxes of the tracer (gas). A first test was performed at Munich-Nord power station with FTIR and cw-Doppler lidar. Fluxes of CO2, CO, NO, and HCl were determined. The results are in good agreement with the fluxes measured byin situ instruments of the power station. The method can be used to control industrial complexes from an outside observation site.

An Advanced Wind Infrared Doppler Lidar (WIND) for Mesoscale Meteorological Studies

Knowledge of the wind field at various scales is widely recognized at the present as fundamental to advancing our understanding and prediction of the weather development. Wind profiles are measured only at a few locations by radiosondes mainly in the northern hemisphere and there on the continents.

Remote Measurements Of Plume Dispersion Over Sea Surface Using The Dfvlr Minilidar

The dispersion of artificial aerosol plumes over sea surfaces was measured using a portable lidar system. The momentary distribution of aerosol concentrations could be derived from short-time measurements. Some effects of the aerosols and the sea surface on the plume dispersion were estimated.