Mesospheric gravity waves over a tropical convective region observed by OH airglow imaging in Indonesia

Abstract

[1] From OH airglow imaging observation carried out over one year in Indonesia, 74 events of gravity waves in the MLT (Mesosphere and Lower Thermosphere) region were extracted. Observed period, horizontal wavelength and observed horizontal phase speeds of gravity waves were typically 5 -13 min, 13-45 km and 37-75 m/s, respectively. Propagation directions were mostly southward except for the period between December and February, when eastward propagation was preferential. Spatial distributions of tropospheric clouds, estimated with GMS (Geostationary Meteorological Satellite) were consistent with the propagation direction of gravity waves, i.e., these clouds mainly existed in the opposite direction to the propagation direction of waves. This suggests that horizontal propagation characteristics of the short period gravity waves in the low latitude MLT region are mainly affected by the distribution of the wave sources in the troposphere, and the effect of the background mean wind in the middle atmosphere is smaller, as it is weaker ($20 m/s) in the equatorial region.

Characteristics and sources of gravity waves observed in noctilucent cloud over Norway

“…The comparison of the average horizontal wavelength of the waves shows reasonable agreement, with a mean value of 24 and 25 km over ∼ 69 and ∼ 62 • N, respectively. Thus, the wave-like perturbations derived from the NLC images in the summer mesosphere are similar in scale from 60 to 74 • N. In addition, they are similar to mesospheric short-period gravity waves observed in the airglow emissions at middle (Taylor et al, 1998), polar (Nielsen et al, 2006) and equatorial latitudes, where peak horizontal wavelengths around 25-30 km were found.…”

“…Although there are a number of gravity-wave studies at high latitudes, most of these rely upon analyzing the wave structures induced by the waves in the night airglow (e.g., Taylor and Henriksen, 1989;Pautet et al, 2005;Nielsen et al, 2006Nielsen et al, , 2009Espy et al, 2004;, Suzuki et al, 20092013). However, these observations are not possible during the high latitude polar summer when the mesosphere remains sunlit.…”

Diurnal variation of short-period (20–120 min) gravity waves in the equatorial Mesosphere and Lower Thermosphere and its relation to deep tropical convection

“…TBB < 230 K is generally considered to represent deep convection (e.g. Nitta and Sekine, 1994). Because the values presented here are monthly mean values, we consider TBB < 250 K as an indication of strong convection.…”

“…We use the cloud-top equivalent black body temperature (TBB) data as a proxy for deep tropical convection (Nitta and Sekine, 1994). Low and high temperatures indicate high and low clouds, respectively.…”

Temperature changes over storms from measurements of spacecraft TIMED

“…In the second category, there were a number of investigations that attempted to explain the prevalence of AGWs in airglow imagers with horizontal wavelength values which are typically several tens of kilometres, have ground-based periods of ten to several tens of minutes, and are imaged a long distance away from a specic convective source [5,12,13,23,26,36,38,40]. Walterscheid et al [40] presented the idea that this was due to ducting of the AGWs in a thermal duct present in the upper mesosphere and lower thermosphere.…”