Mountain Waves Entering the Stratosphere

Abstract

Using the National Science Foundation (NSF)-NCAR Gulfstream V and the NSF-Wyoming King Air research aircraft during the Terrain-Induced Rotor Experiment (T-REX) in March-April 2006, six cases of Sierra Nevada mountain waves were surveyed with 126 cross-mountain legs. The goal was to identify the influence of the tropopause on waves entering the stratosphere. During each flight leg, part of the variation in observed parameters was due to parameter layering, heaving up and down in the waves. Diagnosis of the combined wave-layering signal was aided with innovative use of new GPS altitude measurements. The ozone and water vapor layering correlated with layered Bernoulli function and cross-flow speed.GPS-corrected static pressure was used to compute the vertical energy flux, confirming, for the first time, the Eliassen-Palm relation between momentum and energy flux (EF ϭ ϪU • MF). Kinetic (KE) and potential (PE) wave energy densities were also computed. The equipartition ratio (EQR ϭ PE/KE) changed abruptly across the tropopause, indicating partial wave reflection. In one case (16 April 2006) systematically reversed momentum and energy fluxes were found in the stratosphere above 12 km. On a "wave property diagram," three families of waves were identified: up-and downgoing long waves (30 km) and shorter (14 km) trapped waves. For the latter two types, an explanation is proposed related to secondary generation near the tropopause and reflection or secondary generation in the lower stratosphere.

An example of enhanced tephra deposition driven by topographically induced atmospheric turbulence

“…It results in extreme air turbulence and significant enhancement of vertical atmospheric mixing, and could therefore drive rapid downward acceleration and deposition of particles. Under certain conditions, the instabilities initiated by the breaking of lee waves can propagate upwards, even entering the stratosphere (Smith et al 2008). The effects of lee waves have been extensively reported through observations (Jiang and Doyle 2004;Doyle et al 2005;Smith et al 2007;Lane et al 2009;Jiang et al 2010).…”

Mountain waves modulate the water vapor distribution in the UTLS

“…These layers are disturbed by propagating gravity waves, and an aircraft flying at a constant level penetrates the layers repeatedly, as depicted in Fig. 10 of Smith et al (2008). At a constant altitude, therefore, the trace gas concentration and potential temperature follow the vertical wind variations with a phase shift of 90 • .…”

“…The vertical displacement of an air parcel by gravity waves creates fluctuations in trace gas concentrations at constant altitude if the trace gas distribution has a vertical gradient (Smith et al, 2008). For adiabatic processes, tracer mixing ratios as well as the potential temperature are thereby conserved.…”

“…The method to calculate the vertical trace gas flux (Shapiro, 1980;Schilling et al, 1999) is similar to the calculations of energy and momentum fluxes (e.g., by Smith et al, 2008) and indicates the vertical transport direction of the trace gas. If we assume a negative gradient for the trace gas, a positive flux generally will indicate an upward transport of high mixing ratios into a region with low mixing ratios.…”

“…Gravity waves are known to play an important role in the circulation, structure and variability of the atmosphere (Fritts and Alexander, 2003). They distribute energy and momentum horizontally and vertically in the atmosphere (e.g., Smith et al, 2008;Geller et al, 2013;Wright et al, 2016).…”