An observational estimate of gravity wave drag from the momentum balance in the middle atmosphere.

The zonal average momentum budget in the middle atmosphere is computed for 7 months of satellite observations in order to determine the forcing needed to obtain a balance. This momentum residual includes forcing by waves with small zonal scale, such as gravity waves. The results indicate that the forcing needed in the lower mesosphere reaches peak values of about 20 m s^-1 d^-1, which is large compared to the Rayleigh friction used in that part of the atmosphere in numerical models. -from Authors