Simultaneous observations of mesospheric gravity waves and sprites generated by a midwestern thunderstorm

Abstract

Wescott, E. M.; Picard, R. H.; Winick, J. R.; Stenbaek-Nielsen, H. C.; Dewan, E. M.; Moudry, D. R.; São Sabbas, F. T.; Heavner, M. J.; and Morrill, J., "Simultaneous observations of mesospheric gravity waves and sprites generated by a midwestern thunderstorm" (2003 AbstractThe present report investigates using simultaneous observations of coincident gravity waves and sprites to establish an upper limit on sprite-associated thermal energy deposition in the mesosphere. The University of Alaska operated a variety of optical imagers and photometers at two ground sites in support of the NASA Sprites99 balloon campaign. One site was atop a US Forest Service lookout tower on Bear Mt. in the Black Hills, in western South Dakota. On the night of 18 August 1999 we obtained from this site simultaneous images of sprites and OH airglow modulated by gravity waves emanating from a very active sprite producing thunderstorm over Nebraska, to the Southeast of Bear Mt. Using 25 s exposures with a bare CCD camera equipped with a red ÿlter, we were able to coincidentally record both short duration (¡10 ms) but bright (¿3 MR) N2 1PG red emissions from sprites and much weaker (∼1 kR), but persistent, OH Meinel nightglow emissions. A time lapse movie created from images revealed short period, complete 360• concentric wave structures emanating radially outward from a central excitation region directly above the storm. During the initial stages of the storm outwardly expanding waves possessed a period of ≈10 min and wavelength ≈50 km. Over a 1 h interval the waves gradually changed to longer period ≈11 min and shorter wavelength ≈40 km. Over the full 2 h observation time, about two dozen bright sprites generated by the underlying thunderstorm were recorded near the center of the outwardly radiating gravity wave pattern. No distinctive OH brightness signatures uniquely associated with the sprites were detected at the level of 2% of the ambient background brightness, establishing an associated upper limit of approximately T . 0:5 K for a neutral temperature perturbation over the volume of the sprites. The corresponding total thermal energy deposited by the sprite is bounded by these measurements to be less than ∼1 GJ. This value is well above the total energy deposited into the medium by the sprite, estimated by several independent methods to be on the order of ∼1-10 MJ.

High temporal and spatial-resolution detection of D-layer fluctuations by using time-domain lightning waveforms

“…Ionospheric studies have found evidence of D-layer heating due to thunderstorm quasi-electrostatic fields [Inan et al, 1996;Pasko et al, 1995], evidence of direct heating of the D-layer due to lightning electromagnetic pulses [Cheng and Cummer, 2005;Cheng et al, 2007], and evidence of atmospheric gravity wave (AGW) influence on the E-region ionosphere (100-150 km) [Davis and Johnson, 2005;Johnson and Davis, 2006]. Stratospheric AGW studies have shown neutral density fluctuations at altitudes of 60-90 km due to tropospheric thunderstorms activities [Taylor and Hapgood, 1988;Dewan et al, 1998;Sentman et al, 2003;Yue et al, 2009], and the electron density at this altitude is expected to fluctuate in a similar manner. However, because of low electron densities in the D-layer, it is difficult to continuously measure the electron density and its possible spatial and temporal fluctuations.…”

Thermospheric responses to gravity waves arising from mesoscale convective complexes

“…Observational studies have associated gravity waves near the mesopause with severe storms (Taylor and Hapgood, 1988;Sentman et al, 2003) or correlated mesoscale variance, discrete gravity wave signatures, and wave momentum uxes in the troposphere and lower stratosphere with convection and frontal activity (Larsen et al, 1982;Lu et al, 1984;Kuettner et al, 1987;Fritts and Nastrom, 1992;Hauf, 1993;Pÿster et al, 1993a, b;Alexander and Pÿster, 1995;Sato et al, 1995;Karoly et al, * Corresponding author. Tel.…”

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)

“…3-6) (Dewan et al, 1998;Dhaka et al, 2003;Sentman et al, 2003) during the initial and mature phases of convection for Event 1 and only during the mature phase of convection Event 2 (since the squall line reached GDK in its matured stage): where ω: intrinsic frequency, N: Brunt-Väisälä frequency, m: vertical wave number, k: horizontal wave number, ϕ: elevation angle of group velocity vector, τ : wave period, τ B : Brunt-Väisälä period, λ x : horizontal wavelength, λ z : vertical wavelength; c gx , c gz , c px and c pz are: components of intrinsic group velocity and phase velocity, respectively. The gravity wave parameters from Eqs.…”