Analyzing Waves in Resonance Lidar Data Workshop

Patricia M. Franke, University of Illinois, pfranke@uiwpl.ece.uiuc.edu
Richard L. Collins, University of Alaska, rlc@gi.alaska.edu
NIST 1107, 1:00-3:00 PM
Wednesday, June 28, 2000

A variety of techniques have been developed for studying waves and tides in airglow, lidar and radar data. Typically these techniques employ some simplifying assumption about the atmosphere (e.g. the waves are linear gravity waves that are freely propagating, or that the atmosphere is in hydrostatic equilibrium). Analyses of airglow, lidar, radar data sets suggests that nonlinear wave dynamics may significantly effect the retrieval of atmospheric state variables from the measurement. The goal of this workshop is to consider examples of these phenomena in both Rayleigh and resonance lidar data sets and discuss methods for developing robust retrieval algorithms and reporting for the data. Several strawman data sets will be presented that highlight different phenomena of interest. The workshop session will include prepared presentations highlighting specific topics; wave-breaking and nonlinear interactions in lidar data, tidal analysis of lidar data, mesospheric inversion layers and airglow-lidar studies of waves. We will present some initial results and invite workshop participants to critically assess the techniques and suggest better ways to analyze these phenomena.

Wave-breaking and nonlinear interactions: Doppler wind/temperature lidar data sets from Starfire, NM, will be presented to look at the wave dynamics as represented in the sodium density, temperature and wind measurements. The data sets will be analyzed using non-linear models of gravity waves to study the dynamics of wave breaking and wave-wave interactions in the data. These include identifying regions of instability in the data that yield wave overturning as well as looking at critical layer effects.

Tidal analysis of lidar data: Doppler temperature lidar data will be presented to look at tidal signatures and how they can be retrieved. Simulation results will be presented that show how the tides and waves perturb the sodium layer.

Mesospheric inversion layers: Both ground-based lidars and spaced-based temperature sensors routinely observe perturbation temperatures that are associated with pronounced deviations from the adiabatic lapse rate. These include "layers" wherein temperature increases as a function of mesospheric altitude on the topside, with bottomside lapse rates that are significantly larger than the "unperturbed" state. Many of these so-called inversion layers evolve in a manner that is wholly consistent with propagating gravity wave, planetary wave, or tidal perturbations. We believe that it is important to distinguish between simple wave phenomena and the distinctive class of large MILs. We have initiated a study wherein the global-scale wave model (GSWM) temperature variances are used as a threshold beyond which we identify large MILs in Purple Crow Lidar data. We will also provide a strawman MIL definition and invite everyone to help us to better define these distinctive phenomena.

Airglow-Lidar Studies The OH airglow imager resident at the STARFIRE optical range provides a complementary look at the waves at the mesopause. The waves that this instrument measures best are of a shorter period and horizontal wavelength than those usually seen in lidar data. These waves are important contributors to the dynamics of the region probed by the sodium lidar, so understanding their distribution in frequency, phase speed, and direction is important since the lidar results hold important information about the propagation environment of these waves. Summary results of this distribution for recent campaigns will be presented. propagation environment for these waves.

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