Mesospheric gravity waves observed near equatorial and low–middle latitude stations: wave characteristics and reverse ray tracing results

Abstract

Abstract. Gravity wave signatures were extracted from OH airglow observations using all-sky CCD imagers at four different stations: Cachoeira Paulista (CP) (22.7 • S, 45 • W) and São João do Cariri (7.4 • S, 36.5 • W), Brazil; Tanjungsari (TJS) (6.9 • S, 107.9 • E), Indonesia and Shigaraki (34.9 • N, 136 • E), Japan. The gravity wave parameters are used as an input in a reverse ray tracing model to study the gravity wave vertical propagation trajectory and to estimate the wave source region. Gravity waves observed near the equator showed a shorter period and a larger phase velocity than those waves observed at low-middle latitudes. The waves ray traced down into the troposphere showed the largest horizontal wavelength and phase speed. The ray tracing results also showed that at CP, Cariri and Shigaraki the majority of the ray paths stopped in the mesosphere due to the condition of m 2 <0, while at TJS most of the waves are traced back into the troposphere. In summer time, most of the back traced waves have their final position stopped in the mesosphere due to m 2 <0 or critical level interactions (|m| →∞), which suggests the presence of ducting waves and/or waves generated in-situ. In the troposphere, the possible gravity wave sources are related to meteorological front activities and cloud convections at CP, while at Cariri and TJS tropical cloud convections near the equator are the most probable gravity wave sources. The tropospheric jet stream and the orography are thought to be the major responsible sources for the waves observed at Shigaraki.

Observation of mesospheric gravity waves at Comandante Ferraz Antarctica Station (62° S)

“…Similar analyses were reported by Nakamura et al (1999) and Nakamura et al (2003), at Shigaraki (35 • N) Japan and at Tanjungsari (6.9 • S, hereafter TJS) Indonesia, respectively. Wrasse et al (2006) compared the gravity wave characteristics for 4 distinct stations at equatorial and mid-latitudes. They showed that the horizontal wavelengths observed at CP and Cariri were similar, with a maximum occurrence between 5 and 25 km; at TJS the horizontal wavelength was mainly distributed between 5 and 30 km, while at Shigaraki was between 5 and 40 km.…”

Simultaneous observation of ionospheric plasma bubbles and mesospheric gravity waves during the SpreadFEx Campaign

“…The condition of vertical propagation and dissipation of the waves depends on the wave characteristics (wavelength and phase velocity) and the filtering by the background wind system. In the equatorial mesopause region (80 to 100 km), the gravity waves with a period of 5 to 30 min, horizontal wavelength of 10 to 100 km, phase velocity of 20-80 m/s, are frequently observed by airglow imaging method (Wrasse et al, 2006). Some of these waves have a condition to propagate above 100 km, even up to 200 km in the ionosphere (Vadas and Fritts, 2004).…”

An investigation of long-distance propagation of gravity waves under CAWSES India Phase II Programme

“…Using multi-instrument (imager, Na lidar, MF radar) observations in the range 31-32 • N latitude, Kubota et al (2006) observed a large-scale gravity wave of wavelength ∼ 673-774 km, period ∼ 1.7 h and velocity 107-122 m s −1 . Wrasse et al (2006) investigated the propagation characteristics of gravity waves using the ray-tracing technique at four different stations -Cachoeira Paulista (22.7 • S, 45 • W), Brazil, São João do Cariri (7.4 • S, 36.5 • W), Brazil, Tanjungsari (6.9 • S, 107.9 • E), Indonesia and Shigaraki (34.9 • N, 136 • E), Japan -and found that the source region of the gravity waves was located 1000 km away from the observational site on a few occasions. Recently Suzuki et al (2013) reported observation of gravity waves that propagated in ducts over distances of 1800 km within the 31-44 • N latitude range in Japan.…”