Detection of Low-level-jet Generated Gravity Waves Using a Doppler Wind Lidar and Wave Effect on Momentum and Sensible Heat Vertical Transport

Gravity waves were detected by a Doppler wind lidar in the region of inversion caps in the late mornings due to the strong shear of the low-level-jet (LLJ) and thin layer of stable temperature stratification below the jets. This type of gravity waves occurred quite frequently during the JU2003 experiment. The mechanism of the gravity waves generation by the LLJ is investigated using a linear stability analysis with lidar, radiosonde, and profiler data. The wavelength and phase speed of the wave are computed using the spectral and wavelet methods. Near ground air motions were analyzed using the sonic anemometer data situated in the urban and suburban areas. The time series were separated into three parts, the mean, the wave, and turbulence, using a multi-resolution wavelet analysis technique. Vertical momentum and heat fluxes from wave motion are very large compared with the turbulent fluxes. The wave fluxes probably accelerated boundary layer growth during the morning hours.