Observation and modeling of gravity wave propagation through reflection and critical layers above Andes Lidar Observatory at Cerro Pachón, Chile

Abstract

A complex gravity wave event was observed from 04:30 to 08:10 UTC on 16 January 2015 by a narrow‐band sodium lidar and an all‐sky airglow imager located at Andes Lidar Observatory (ALO) in Cerro Pachón (30.25°S, 70.73°W), Chile. The gravity wave packet had a period of 18–35 min and a horizontal wavelength of about 40–50 km. Strong enhancements of the vertical wind perturbation, exceeding 10 m s−1, were found at ∼90 km and ∼103 km, consistent with nearly evanescent wave behavior near a reflection layer. A reduction in vertical wavelength was found as the phase speed approached the background wind speed near ∼93 km. A distinct three‐layered structure was observed in the lidar data due to refraction of the wave packet. A fully nonlinear model was used to simulate this event, which successfully reproduced the amplitudes and layered structure seen in observations. The model results provide dynamical insight, suggesting that a double reflection occurring at two separate heights caused the large vertical wind amplitudes, while the three‐layered structure in the temperature perturbation was a result of relatively stable regions at those altitudes. The event provides a clear perspective on the filtering processes to which short‐period, small‐scale gravity waves are subject in mesosphere and lower thermosphere.

First tomographic observations of gravity waves by the infrared limb imager GLORIA

“…Consequences of these GW parameterizations are for example surface temperature uncertainties of up to 2 K (Sigmond and Scinocca, 2010) and pressure discrepancies of several hPa at polar latitudes (Sandu et al, 2016) in climate projections. Improved weather predictions and climate projections therefore require more advanced parameterization schemes as proposed by various studies (Kim et al, 2013;Bushell et al, 2015;de la Camara and Lott, 2015;Amemiya and Sato, 2016).…”

Numerical Simulations of High‐Frequency Gravity Wave Propagation Through Fine Structures in the Mesosphere

“…Our results identify the tendency for subkilometer FS layers with low initial amplitudes to form GW-scale instabilities and further evaluate the instability morphologies for different layer compositions, diagnosing the consequences of layer directionality and how they influence the background wind. It is worth noting that shear and stability FS observed in the MLT often have much larger magnitudes than those examined in this study (see, e.g., Bossert et al, 2015Bossert et al, , 2016Cao et al, 2016;Fritts, Pautet, et al, 2014); that GW propagation through relatively weak FS produces such significant impacts on the tendencies for GW dissipation and momentum deposition suggests that such events in the atmosphere having comparable or stronger FS features will have comparable or larger impacts on GW propagation and momentum transport and deposition.…”

Gravity Wave Ducting Observed in the Mesosphere Over Jicamarca, Peru

“…A nonlinear, two‐dimensional numerical model was used to simulate the observed GW processes (Snively et al, ; Snively & Pasko, , and references therein). The model has been used extensively to investigate the propagation, dissipation, and interaction of GWs in the mesosphere and lower thermosphere and for comparisons with observed data (Cao et al, ; Heale et al, ; Simkhada et al, ). The background meridional wind profile (Figure ) was modeled with a Gaussian centered at 71 km, a maximum southward wind of 50 m/s, and turning northward below 69 and above 75 km.…”

“…Bossert et al () combined OH airglow temperature maps with winds, temperatures, and density perturbations from sodium lidar to study a GW ducting event at high latitudes. Cao et al () analyzed airglow intensity combined with temperature and vertical wind structures from sodium lidar at midlatitudes and compared them with a model simulation of a GW packet propagating through multiple ducts. Noctilucent or polar mesospheric clouds are also a well‐known tracer for GW activity.…”