Concentric gravity waves over northern China observed by an airglow imager network and satellites

Self Cite

The Tibetan Plateau (TP), known as “Third Pole” of the Earth, has important influences on global climates and local weather. An important objective in present study is to investigate how orographic features of the TP affect the geographical distributions of gravity wave (GW) sources. Three‐year OH airglow images (November 2011 to October 2014) from Qujing (25.6°N, 103.7°E) were used to study the characteristics of GWs over the southeastern TP region. Along with the almost concurrent and collocated meteor radar wind measurements and temperature data from SABER/TIMED satellite, the propagation conditions of three types of GWs (freely propagating, ducted, or evanescent) were estimated. Most of GWs exhibited ducted or evanescent characteristics. Almost all GWs propagate southeastward in winter. The GW propagation directions in winter are significantly different from other airglow imager observations at northern middle latitudes. Wind data and convective precipitation fields from the European Centre for Medium‐Range Weather Forecasts reanalysis data are used to study the sources of GWs on the edge of the TP. Using backward ray‐tracing analysis, we find that most of the mesospheric freely propagating GWs are located in or near the large wind shear intensity region (~10 km–~17 km) on the southeastern edge of the TP in spring and winter. The averaged value of momentum flux is 11.6 ± 5.2 m2/s2 in winter and 7.5 ± 3.1 m2/s2 in summer. This work will provide valuable information for the GW parameterization schemes in general circulation models in TP region.

Section: Resultsmentioning

confidence: 96%

Characteristics of mesospheric gravity waves over the southeastern Tibetan Plateau region

Liu

et al. 2016

Self Cite

“…The generated gravity waves can propagate upward and can modulate the airglow layers in the 80-100 km height range [Taylor and Hapgood, 1988;Taylor et al, 2007;Snively and Pasko, 2008]. Using the imaging nighttime airglow from ground observation sites [Taylor and Hapgood, 1988;Swenson and Mende, 1994;Chung et al, 2003;Sentman et al, 2003;Taylor et al, 2007;Suzuki et al, 2013;Xu et al, 2015] or spaceborne observation [Dewan et al, 1998;Mende et al, 1998;Yue et al, 2013;Akiya et al, 2014;Xu et al, 2015], gravity waves can be easily identified and observed. In addition, storm-generated gravity waves have also been confirmed by GPS data [Horinouchi and Tsuda, 2009;Lay et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

Simultaneous observations of storm‐generated sprite and gravity wave over Bangladesh

Chou

Dai²,

Kuo

et al. 2016

We report simultaneous observations of sprite and gravity wave generated by a storm over Bangladesh. The origin of a concentric gravity wave can be traced to the storm region on 27 April 2014 over Bangladesh with a low cloud top surface temperature (175 K). After data analysis, the time period of the concentric gravity wave is found to be 8.8–8.9 min. The horizontal wavelength is found to be ~50 km for red emissions (~55 km for green emissions), and the horizontal phase velocity is 94.4 ± 31.7 m s−1 for red emissions (102.6 ± 29.4 m s−1 for green emissions). Using the dispersion relation of gravity wave, the elevation angle of wave propagation direction is found to be ~53.3°. The sprite associated with the gravity wave was also recorded at 1534 UT on 27 April 2014. The initiation time of storm‐generated gravity wave is estimated to be 1454 UT at which lightning activity was relatively low using lightning data. At time 1534 UT of the recorded sprite, the lightning rate was close to its maximum value. The storm‐generated gravity wave could be thought as a precursor phenomenon for lightning and sprites since one of the necessary conditions for gravity wave, lightning, and sprites is strong convection inside storms.

“…The nonuniform distribution of wave sources around an observation station is an important factor to determine the anisotropy of the GWs propagation directions. Convective activity is an important source of high‐frequency GWs, which has been revealed from observations in the lower and middle latitudes (Li et al, ; Nakamura et al, ; Xu et al, ) and simulations (Alexander et al, , ; Vadas & Fritts, ; Walterscheid et al, ). Figure shows the distributions of convective precipitations derived from ECMWF reanalysis data.…”

Section: Resultsmentioning

confidence: 98%

“…The atmospheric circulation and structure in turn has important influences on local weather and global climates (McLandress et al, 2012). Convection, front/jet stream, orography, and wind shear in the troposphere are important sources of GWs (Eckermann & Vincent, 1993;Fritts, 1982Fritts, , 1984Li et al, 2016;Nakamura et al, 2003;Xu et al, 2015;Zhang, 2004). The auroral processes can also generate GWs (Oyama & Watkins, 2012).…”

Section: Introductionmentioning

confidence: 99%

First OH Airglow Observation of Mesospheric Gravity Waves Over European Russia Region

Yusupov

Akchurin

et al. 2018

Self Cite

For the first time, we perform a study of mesospheric gravity waves (GWs) for four different seasons of 1 year in the latitudinal band from 45°N to 75°N using an OH all‐sky airglow imager over Kazan (55.8°N, 49.2°E), Russia, during the period of August 2015 to July 2016. Our observational study fills a huge airglow imaging observation gap in Europe and Russia region. In total, 125 GW events and 28 ripple events were determined by OH airglow images in 98 clear nights. The observed GWs showed a strong preference of propagation toward northeast in all seasons, which was significantly different from airglow imager observations at other latitudes that the propagation directions were seasonal dependent. The middle atmosphere wind field is used to explain the lack of low phase speed GWs since these GWs were falling into the blocking region due to the filtering effects. Deep tropospheric convections derived from the European Centre for Medium‐Range Weather Forecasts reanalysis data are determined near Caucasus Mountains region, which suggests that the convections are the dominant source of the GWs in spring, summer, and autumn seasons. This finding extends our knowledge that convection might also be an important source of GWs in the higher latitudes. In winter the generation mechanism of the GWs are considered to be jet stream systems. In addition, the occurrence frequency of ripple is much lower than other stations. This study provides some constraints on the range of GW parameters in GW parameterization in general circulation models in Europe and Russia region.