A simple model of gravity-wave momentum and energy fluxes transferred through the middle atmosphere to the upper atmosphere

Orthonormal wavelet analysis is applied for the first time to two-dimensional (time and height) data obtained from three-week continuous MU radar observations in June-July, 1991. It is confirmed that monochromatic wave structures are generally localized both in time and in altitude. We find the dominant temporal scale of wave activity in this case study is 2-4 days. The dominant vertical wavelength seems to decrease from -4 km to -1 km, upwards through the tropopause-lower stratosphere region, which is almost independent of temporal scales in the 1-4 day range.

Section: Discussion In Comparison With Mean Wind Profilesupporting

confidence: 87%

Application of Two-Dimensional Wavelet Analysis to Wind Disturbances Observed with MU Radar in the Lower Stratosphere and Troposphere

Shimomai

Yamanaka

Fukao

1997

“…Considering the upward exponential decrease (only 20% inside the PBL and about one order of magnitude in the free troposphere) of atmospheric density, we consider that the kinetic energy increases at least about 8 times from the bottom to the top of the PBL, decreases about one order from the PBL to the upper troposphere, and again decreases two or three orders from the tropopause to the mesopause. Although the upward decrease of wave energy in the extra-tropical middle atmosphere has been previously reported (e.g., Tsuda et al, 1994a;Yamanaka and Fukao, 1994 Fig. 4.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 84%

Frequency Spectra of Wind Velocity Fluctuations between 1 hour and 1 month in the Atmospheric Boundary Layer over Equatorial Indonesia

Hashiguchi

Fukao

Yamanaka

et al. 1997

Self Cite

Frequency power spectra are analyzed from zonal and meridional wind velocities observed continuously in a height range below 2.5 km with the Kyoto University Boundary Layer Radar (BLR) in Serpong, Indonesia (6.4°S, 106.7°E). We find that (i) the spectral slope in a period range from a few hours to a few days is approximately -1; (ii) the power spectral densities in the rainy season are at least about two times larger than those in the dry season; (iii) the diurnal component is dominant both in dry and rainy seasons; (iv) components with periods of about 4 and 10 days are probably associated with mixed Rossbygravity wavelike cloud clusters and Kelvin wavelike super cloud clusters, respectively; and (v) the power spectral amplitudes increase at least one order of magnitude from the bottom to the top of the equatorial Planetary Boundary Layer (PBL), and the values at the top of the PBL are comparable to those in the upper troposphere over mid-latitudes. The last feature suggests that the equatorial PBL is probably a major source of kinetic energy of the earth's atmosphere.

“…5.2 Energy flux in internal gravity waves Yamanaka and Fukao (1994) have presented a semi-empirical analysis of energy fluxes in gravity waves and estimate that at 100 km altitude the vertical energy flux in these waves is 4 erg cm-2 S-1. Internal gravity waves at frequencies well below the Brunt-Vaisala frequency propagate energy very slowly in the vertical direction (Hines, 1960).…”

Section: Energy Content Of Neutral Atmospherementioning

confidence: 99%

“…Next it has been shown by Hooke (1968) that gravity waves of velocity amplitude 20 ins-' are capable of accounting for a range of F-region ionospheric irregularities at mid-latitudes. Except for the first entry which comes from Yamanaka and Fukao (1994) where Vg, ,, is the vertical component of the group velocity of gravity waves, and Ipnvn is the kinetic energy density of a characteristic wave, and vn is the velocity amplitude of the wave. The real formula is much more complex mathematically (e.g., Kato, 1980).…”

Section: Energy Content Of Neutral Atmospherementioning

confidence: 99%

“…In this respect measurements of these winds and fluxes at E-region conjugate points to the FAI are fundamental. Mid latitude measurements of gravity waves have lead Yamanaka and Fukao (1994) to infer that the energy flux of gravity waves at 100 km altitude is about 3 erg cm-2 cm 1. Longitudinal variations in the occurrence of FAI's would then be related dominantly to the sources of these fluxes from the atmosphere at lower altitudes, and with atmospheric disturbances there.…”

Section: Flux Of Energy In Winds and Gravity Wavesmentioning

confidence: 99%

See 1 more Smart Citation

Equatorial Thermosphere-Ionosphere-Plasmasphere Disturbances.

Cole

1996

A theory of equatorial thermosphere-ionosphere-plasmasphere (magnetosphere) disturbances creating field aligned irregularities is extended here. Further development is given of the hypothesis of the transfer of electrostatic fields and currents from the B-region dynamo to the conjugate F-region, topside ionosphere, and plasmasphere, involving field-aligned currents. Conditions are found such that dynamo action in the ionosphere controls the formation of large-scale magnetic field-aligned irregularities. Sporadic-E layers involving Fe+, and/or other long-lasting ions, may play a special role in the process. General conditions are found under which the discharge of ionospheric currents across the geomagnetic field in the magnetosphere is a significant factor. An energy analysis is conducted of the processes involved in the formation of the irregularities. This suggests that there is a large class of equatorial ionosphere-plasmasphere irregularities whose source of energy is in the conjugate -regions. Alternatively stated, winds and gravity waves in the conjugate point B-regions are a significant source of energy for the equatorial F-region and topside plasmasphere where it is dissipated as joule heat, viscous heating and compressional heating of plasma followed by heat conduction in the neutral gas. Dynamo processes in the conjugate B-regions are a significant source of energy also for the nightside equatorial thermosphere at F region and higher altitudes.