Lidar observations of fine-scale internal gravity waves

More than fifty episodes of internal gravity waves were identified in data collected by the Raman-shifted Eye-safe Aerosol Lidar (REAL) in Dixon, California, from March to June 2007. The REAL provided two-dimensional spatial data in the form of horizontal cross-sectional images of aerosol backscatter intensity. This data is high pass median filtered and from that we can determine the wavelength and propagation velocity of the waves. To be included in this study, wave structures of coherent aerosol bands must have propagated through a 30 m tower installed 1.61 km south of the lidar and existed for longer than one minute. Instruments on the tower included three-component sonic anemometers, relative humidity sensors, and thermometers that provided time-series of in situ data at multiple altitudes. This temporal data allowed the measurement of wave period and calculations of relevant quantities such as Brunt-Vaisala frequency and thermal flux. All cases occurred during the night under statically stable conditions. The figure below shows one lidar image and in situ data for one of the more than fifty episodes.