We investigate the effects on the mesosphere and thermosphere from a strong mountain wave (MW) event over the wintertime Southern Andes using a gravity wave (GW)‐resolving global circulation model. During this event, MWs break and attenuate at
We present a new version of the high‐resolution Kühlungsborn Mechanistic general Circulation Model (KMCM) extended to
- Award ID(s):
- 1832988
- NSF-PAR ID:
- 10375520
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 125
- Issue:
- 10
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract z ∼50–80 km, thereby creating local body forces that generate large‐scale secondary GWs having concentric ring structure with horizontal wavelengthsλ H =500–2,000 km, horizontal phase speedsc H =70–100 m/s, and periodsτ r ∼3–10 hr. These secondary GWs dissipate in the upper mesosphere and thermosphere, thereby creating local body forces. These forces have horizontal sizes of 180–800 km, depending on the constructive/destructive interference between wave packets and the overall sizes of the wave packets. The largest body force is atz =80–130 km, has an amplitude of ∼2,400 m/s/day, and is located ∼1,000 km east of the Southern Andes. This force excites medium‐ and large‐scale “tertiary GWs” having concentric ring structure, withλ H increasing with radius from the centers of the rings. Near the Southern Andes, these tertiary GWs havec H =120–160 m/s,λ H =350–2,000 km, andτ r ∼4–9 hr. Some of the larger‐λ H tertiary GWs propagate to the west coast of Africa with very large phase speeds ofc H ≃420 m/s. The GW potential energy density increases exponentially atz ∼95–115 km, decreases atz ∼115–125 km where most of the secondary GWs dissipate, and increases again atz >125 km from the tertiary GWs. Thus, strong MW events result in the generation of medium‐ to large‐scale fast tertiary GWs in the mesosphere and thermosphere via this multistep vertical coupling mechanism. -
Abstract We analyze quiet‐time data from the Gravity Field and Ocean Circulation Explorer satellite as it overpassed the Southern Andes at
z ≃275 km on 5 July 2010 at 23 UT. We extract the 20 largest traveling atmospheric disturbances from the density perturbations and cross‐track winds using Fourier analysis. Using gravity wave (GW) dissipative theory that includes realistic molecular viscosity, we search parameter space to determine which hot spot traveling atmospheric disturbances are GWs. This results in the identification of 17 GWs having horizontal wavelengthsλ H = 170–1,850 km, intrinsic periodsτ I r = 11–54 min, intrinsic horizontal phase speedsc I H = 245–630 m/s, and density perturbations0.03–7%. We unambiguously determine the propagation direction for 11 of these GWs and find that most had large meridional components to their propagation directions. Using reverse ray tracing, we find that 10 of these GWs must have been created in the mesosphere or thermosphere. We show that mountain waves (MWs) were observed in the stratosphere earlier that day and that these MWs saturated at z ∼ 70–75 km from convective instability. We suggest that these 10 Gravity Field and Ocean Circulation Explorer hot spot GWs are likely tertiary (or higher‐order) GWs created from the dissipation of secondary GWs excited by the local body forces created from MW breaking. We suggest that the other GW is likely a secondary or tertiary (or higher‐order) GW. This study strongly suggests that the hot spot GWs over the Southern Andes in the quiet‐time middle winter thermosphere cannot be successfully modeled by conventional global circulation models where GWs are parameterized and launched in the troposphere or stratosphere. -
Abstract We examine the total electron content (TEC) from GPS receivers over the United States on March 25–26, 2015. We observe partial to nearly fully concentric rings of traveling ionospheric disturbances (TIDs) with centers close to deep convection. Many of these TIDs have observed horizontal phase speeds
c H > 300 m/s, suggesting they are induced by gravity waves (GWs) created in the thermosphere. We investigate the largest‐amplitude concentric TIDs at 23:00 UT on March 25 and 01:20 UT on March 26. We find thatc Hand the GW periodτ rincrease linearly with radius and the horizontal wavelength,λ H, increases quadratically with radius. This is expected if the GWs are excited by point sources. For these GWs,c H = 150–530 m/s,τ r ∼ 8–40 min, andλ H ∼ 100–500 km. Using reverse ray‐tracing, no GW withc H > 200 m/s propagates belowz = 100 km, 73% of the GWs in the first case cannot propagate belowz ∼ 100 km, all of the GWs in the second case cannot propagate belowz ∼ 100 km, and the inferred thermospheric point sources are ∼2–4° from deep convection. Because the underlying GWs are most likely excited by a point source and most must be created in the thermosphere, we find that these concentric TIDs are most likely induced by GWs generated in the thermosphere, including those withc H = 150–200 m/s. Their close proximity to deep convection and the TEC map asymmetries suggest these TIDs are likely induced by secondary GWs from local horizontal body forces created by the dissipation of primary GWs from deep convection. -
Abstract We analyze the gravity waves (GWs) observed by a Rayleigh lidar at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) (16.08°E, 69.38°N) in Norway at
z ∼ 20–85 km on 12–14 January 2016. These GWs propagate upward and downward away fromz knee = 57 and 64 km at a horizontally‐displaced location with periodsτ r ∼ 5–10 hr and vertical wavelengthsλ z ∼ 9–20 km. Because the hodographs are distorted, we introduce an alternative method to determine the GW parameters. We find that these GWs are medium to large‐scale, and propagate north/northwestward with intrinsic horizontal phase speeds of ∼35–65 m/s. Since the GW parameters are similar above and belowz knee, these are secondary GWs created by local body forces (LBFs) south/southeast of ALOMAR. We use the nudged HIAMCM (HIgh Altitude Mechanistic general Circulation Model) to model these events. Remarkably, the model reproduces similar GW structures over ALOMAR, withz knee = 58 and 66 km. The event #1 GWs are created by a LBF at ∼35°E, ∼60°N, andz ∼ 58 km. This LBF is created by the breaking and dissipation of primary GWs generated and amplified by the imbalance of the polar night jet below the wind maximum; the primary GWs for this event are created atz ∼ 25–35 km at 49–53°N. We also find that the HIAMCM GWs agree well with those observed by the Atmospheric InfraRed Sounder (AIRS) satellite, and that those AIRS GWs south and north of ∼50°N over Europe are mainly mountain waves and GWs from the polar vortex, respectively. -
Abstract “Ultra‐fast” Kelvin waves (UFKWs) serve as a mechanism for coupling the tropical troposphere with the mesosphere, thermosphere and ionosphere. Herein, solutions to the linearized wave equations in a dissipative thermosphere in the form of “Hough Mode Extensions (HMEs)” are employed to better understand the vertical propagation of the subset of these waves that most effectively penetrate into the thermosphere above about 100 km altitude; namely, UFKWs with periods ≲4 days, vertical wavelengths (
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