COSMIC GPS Observations of Northern Hemisphere winter stratospheric gravity waves and comparisons with an atmospheric general circulation model

Abstract

COSMIC satellite temperature data are used to derive the 2006/07 winter mean stratospheric Northern Hemisphere potential energy Ep from gravity waves with vertical wavelengths less than 7 km in grid cells of size 10° × 5°; and to study longitudinal and latitudinal variability in cells of size 20° × 5° × 7 days. Large Ep at 17–23 km is mostly associated with the sub‐tropical jet and shows significant longitudinal variability. Some contribution to total Ep from local orographic sources may occur above the Canadian Rockies, Scandinavia and northern Japan, but not above the Himalayas, due to the background wind conditions. Many of the waves are likely to have low ground‐based phase speeds, as observed by filtering around the 0–10 m s−1 background zonal wind. COSMIC results are compared with a T106L60 AGCM, confirming sub‐tropical jet related generation, upward propagation and low phase speeds of the observed gravity waves.

Global distribution of vertical wavenumber spectra in the lower stratosphere observed using high-vertical-resolution temperature profiles from COSMIC GPS radio occultation

“…These results are basically consistent with Alexander et al (2008a). Note that E T p tended to become larger at low latitudes below about 25 • N, which is more clearly recognized in region (b) (Fig.…”

“…The ratio at 10 • S-10 • N latitude showed a steady enhancement, exceeding 1.0, regardless of season and longitude. The ratio at middle latitudes in the NH in region (a) was significantly enhanced in winter, being close to 1.0, suggesting the evident effects of topography in generating GWs by the Tibetan Plateau, located at around 30-50 • N ( Alexander et al, 2008a;Hei et al, 2008). At 50-80 • N the ratio was about 0.6-0.75 in winter, again indicating a relationship with topography (refer to Fig.…”

“…Murayama et al (1994) reported a clear correlation between GW activity and the magnitude of subtropical jet streams using Middle and Upper Atmosphere Radar (MU) observations. Orographic generation of GWs has previously been observed with balloon soundings and satellite measurements over the Andes (Alexander et al, 2008a) and Antarctica (Baumgaertner and McDonald, 2007;Sato and Yoshiki, 2008). Effects of the polar night jet and sudden stratospheric warming events on GW excitation have also been studied (Yoshiki et al, 2004;Hei et al, 2008).…”

“…It is reported that the topography over the Tibetan Plateau, Rocky Mountains, and Andes contributes to the generation of GWs (e.g. Alexander et al, 2008a). In the tropics, GWs are emitted by convective clouds .…”

Investigation of convectively generated gravity wave characteristics and generation mechanisms during the passage of thunderstorm and squall line over Gadanki (13.5° N, 79.2° E)

“…Since the sources of short GWs are most likely found in the middle and upper tropospheres, their propagation direction is mostly upward. We apply the CWT analysis to the perturbed vertical velocity (as in Alexander et al, 2008;Schmidt et al, 2008;Llamedo et al, 2009;de la Torre et al, 2011de la Torre et al, , 2012Hierro et al, 2012) to obtain the dominant modes between 4 min and 120 min. In order to distinguish the CGWs from other oscillations such as GWs, which are generated by turbulent wind shear and buoyancy oscillations, the data are classified into three parts.…”