Gravity wave momentum flux in the upper mesosphere derived from OH airglow imaging measurements

Abstract

We report procedures to identify small-scale (20-100 km) atmospheric gravity waves from OH airglow images to estimate momentum fluxes carried by the waves. We also deduce contamination of background continuum emission in OH image, by comparing a simultaneous observation of OH lines measured by the Spectral Airglow Temperature Imager (SATI). We applied the procedures to a one-night dataset obtained at Shigaraki, Japan (34.9• N, 136.1 • E) on November 19, 1999. The background wind, which is essential for deriving the intrinsic parameters of gravity waves, was measured by the Middle and Upper Atmosphere (MU) radar. Contamination of background continuum emission with the OH filter was deduced to be 30%. From these procedures, we found that the gravity waves identified in the OH images were mainly propagating southward or southeastward with horizontal wavelengths of 60-90 km and apparent phase speeds of 40-80 m/s. The estimated momentum fluxes on this night was 1-15 m 2 s −2 , with an average of 4.9 m 2 s −2 .

Investigation of gravity waves using horizontally resolved radial velocity measurements

“…Further, it was possible to test the decomposition of the wind field using synthetic data to investigate whether the GW properties were preserved within the radial velocity variation images. Our analysis shows that the outlined imaging technique permits to extract the GW properties for monochromatic waves similar to airglow observations (e.g., Nielsen et al, 2006;Suzuki et al, 2007).…”

“…To investigate the horizontal variability of the wind field we developed an imaging technique similar to the OHemission observations (e.g., Suzuki et al, 2010). Considering the approach of Browning and Wexler (1968), the wind field is decomposed into mean winds and the first-order gradient wind terms from Eq.…”

“…The meridional, zonal and vertical GW amplitudes are coupled by the linear polarization relations for GW. The vertical wavelength is given by the dispersion equation (e.g., Fritts and Alexander, 2003;Suzuki et al, 2010) for short-period GW.…”

“…There are several in situ (e.g., Eckermann and Vincent, 1989;Theuerkauf et al, 2011) and ground-based observation techniques like, e.g., meteor radars (e.g., Hocking, 2005;Fritts et al, 2010b, a;Placke et al, 2011), MF radars (e.g., Hoffmann et al, 2010Hoffmann et al, , 2011Placke et al, 2013), lidars (e.g., Rauthe et al, 2006;Gerding et al, 2008), airglow imagers (e.g., Nakamura et al, 1999;Pautet and Moreels, 2002;Suzuki et al, 2004Suzuki et al, , 2010 or CCD images of noctilucent clouds (NLC) (e.g., Pautet et al, 2011) as well as satelliteborne observations (e.g., Preusse et al, 2000;Ern et al, 2004Ern et al, , 2011 to quantify the properties of gravity waves and their effect on the background flow. Here we investigate short-period gravity waves using horizontally resolved radar observations.…”

Investigation of a mesospheric gravity wave ducting event using coordinated sodium lidar and Mesospheric Temperature Mapper measurements at ALOMAR, Norway (69°N)

“…A number of studies have also addressed the specific dynamics needs noted above. These include estimates of MLT GW momentum fluxes employing various techniques [e.g., Vincent and Reid, 1983;Fritts and Vincent, 1987;Reid and Vincent, 1987;Reid et al, 1988;Meyer et al, 1989;Tsuda et al, 1990;Wang and Fritts, 1990;Hitchman et al, 1992;Murphy and Vincent, 1993;Nakamura et al, 1993;Swenson et al, 1999;Gavrilov et al, 2000;Espy et al, 2004Espy et al, , 2006Suzuki et al, 2007;Antonita et al, 2008;Fritts et al, 2010Fritts et al, , 2012. Other studies yielded direct evidence for local instabilities suggesting GW "breaking," dissipation, and energy and momentum deposition [e.g., Swenson and Mende, 1994;Hecht et al, 1997;Yamada et al, 2001;Xu et al, 2006;Li et al, 2005Li et al, , 2007.…”