Three-Dimensional Characteristics of Stratospheric Mountain Waves during T-REX

Abstract

Measurements from the National Science Foundation/National Center for Atmospheric Research (NSF/ NCAR) Gulfstream V (G-V) obtained during the recent Terrain-Induced Rotor Experiment (T-REX) indicate marked differences in the character of the wave response between repeated flight tracks across the Sierra Nevada, which were separated by a distance of approximately 50 km. Observations from several of the G-V research flights indicate that the vertical velocities in the primary wave exhibited variations up to a factor of 2 between the southern and northern portions of the racetrack flight segments in the lower stratosphere, with the largest amplitude waves most often occurring over the southern flight leg, which has a terrain maximum that is 800 m lower than the northern leg. Multiple racetracks at 11.7-and 13.1-km altitudes indicate that these differences were repeatable, which is suggestive that the deviations were likely due to vertically propagating mountain waves that varied systematically in amplitude rather than associated with transients. The cross-mountain horizontal velocity perturbations are also a maximum above the southern portion of the Sierra Nevada ridge.Real data and idealized nonhydrostatic numerical model simulations are used to test the hypothesis that the observed variability in the wave amplitude and characteristics in the along-barrier direction is a consequence of blocking by the three-dimensional Sierra Nevada and the Coriolis effect. The numerical simulation results suggest that wave launching is sensitive to the overall three-dimensional characteristics of the Sierra Nevada barrier, which has an important impact on the wave amplitude and characteristics in the lower stratosphere. Real-time high-resolution Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) forecasts successfully capture the along-barrier variations in the wave amplitude (using vertical velocity as a proxy) as well as skillfully distinguishing between large-and small-amplitude stratospheric wave events during T-REX.

Variance-Based Sensitivity Analysis: Preliminary Results in COAMPS

“…The shortwave and longwave radiation processes are represented following Harshvardhan et al (1987). Results from COAMPS model simulations have been evaluated on numerous occasions using special observations and field campaign datasets and have been demonstrated to accurately simulate mesoscale flows (e.g., Hodur 1997; Doyle et al 2011;Jiang and Doyle 2009).…”

An Intercomparison of T-REX Mountain-Wave Simulations and Implications for Mesoscale Predictability

“…1), which was one of the stronger mountain wave cases observed during T-REX Smith et al 2008;Doyle et al 2010). The wind component parallel to the T-REX -B‖ flight track (245°) is used for the initial state.…”

Dynamics of Orographic Gravity Waves Observed in the Mesosphere over the Auckland Islands during the Deep Propagating Gravity Wave Experiment (DEEPWAVE)

“…Highresolution regional forecasts centered over Auckland Island using the U.S. Naval Research Laboratory (NRL) Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS: Hodur 1997; Doyle et al 2011) and Mountain Wave Forecast Model (Eckermann et al 2006b) predicted wave generation and penetration of orographic gravity waves into the stratosphere. Accordingly, the RF23 flight track was devised, among other things, to profile possible deep orographic gravity waves over Auckland Island.…”