TY - JOUR

T1 - Statistical analysis of gravity waves observed with the middle and upper atmosphere radar in the middle atmosphere 1. Method and general characteristics

AU - Gavrilov, N. M.

AU - Fukao, S.

AU - Nakamura, T.

AU - Tsuda, T.

AU - Yamanaka, M. D.

AU - Yamamoto, M.

PY - 1996/12/27

Y1 - 1996/12/27

N2 - A statistical procedure is developed to obtain the parameters of spectral harmonics of internal gravity waves (IGW) with horizontal wavelengths larger than ∼ 60 km using measurements of wind velocity in the middle atmosphere from the middle and upper atmosphere (MU) radar. The method is applied to find sets of IGW parameters for the winter and summer seasons of 1987-1988 for 6-km-thick layers centered at 70, 75, and 80 km at Shigaraki, Japan (34.9°N, 139.4°E). The numbers of selected IGW harmonics having periods from 5 min up to 6 hours vary between 360 and 2000 depending on the season and altitude. Mean vertical wave numbers are 0.6-0.9 km-1 in winter and 0.5-1 km-1 in summer, and horizontal wave numbers are (3-4)×10-2 km-1 and (2-4)×10-2 km-1, respectively. Predominant azimuths of wave vectors and momentum fluxes concentrate near 64° in winter and 90° in summer at all altitudes. In general, the difference between the azimuths of the wave vector and momentum flux is close to zero or 180°. Turbulent and instrumental noise can contribute 20-30% of the observed intensity of the wind variations at altitudes of 70-85 km. The IGW momentum fluxes are 0.2-2.7 m2s-2 in winter and 0.2-1.9 m2s-2 in summer. The wave drag of the mean flow is 0.5-45 m2s-1 in winter and 2-25 m2s-1 in summer. In most cases the momentum flux and wave drag are directed oppositely to the mean wind.

AB - A statistical procedure is developed to obtain the parameters of spectral harmonics of internal gravity waves (IGW) with horizontal wavelengths larger than ∼ 60 km using measurements of wind velocity in the middle atmosphere from the middle and upper atmosphere (MU) radar. The method is applied to find sets of IGW parameters for the winter and summer seasons of 1987-1988 for 6-km-thick layers centered at 70, 75, and 80 km at Shigaraki, Japan (34.9°N, 139.4°E). The numbers of selected IGW harmonics having periods from 5 min up to 6 hours vary between 360 and 2000 depending on the season and altitude. Mean vertical wave numbers are 0.6-0.9 km-1 in winter and 0.5-1 km-1 in summer, and horizontal wave numbers are (3-4)×10-2 km-1 and (2-4)×10-2 km-1, respectively. Predominant azimuths of wave vectors and momentum fluxes concentrate near 64° in winter and 90° in summer at all altitudes. In general, the difference between the azimuths of the wave vector and momentum flux is close to zero or 180°. Turbulent and instrumental noise can contribute 20-30% of the observed intensity of the wind variations at altitudes of 70-85 km. The IGW momentum fluxes are 0.2-2.7 m2s-2 in winter and 0.2-1.9 m2s-2 in summer. The wave drag of the mean flow is 0.5-45 m2s-1 in winter and 2-25 m2s-1 in summer. In most cases the momentum flux and wave drag are directed oppositely to the mean wind.

UR - http://www.scopus.com/inward/record.url?scp=0030369191&partnerID=8YFLogxK

U2 - 10.1029/96jd01447

DO - 10.1029/96jd01447

M3 - Article

AN - SCOPUS:0030369191

VL - 101

SP - 29511

EP - 29521

JO - Journal of Geophysical Research: Biogeosciences

JF - Journal of Geophysical Research: Biogeosciences

SN - 0148-0227

IS - 23

ER -