Chihoko Yamashita

Stratospheric gravity wave characteristics and seasonal variations observed by lidar at the South Pole and Rothera, Antarctica

� 0.7 m s � 1 , and period of � 104 min. Approximately 44% of the observed waves show an upward phase progression while the rest display a downward phase progression in ground-based reference for both locations. Gravity wave potential energy density (GW-EP) at Rothera is � 4 times higher than the South Pole in winter but is comparable in summer. Clear seasonal variations of GW-EP are observed at Rothera with the winter average being 6 times larger than that of summer. The seasonal variations of GW-EP at the South Pole are significantly smaller than those at Rothera. The absence of seasonal variations in wave sources and critical level filtering at the South Pole is likely to be responsible for the nearly constant GW-EP. The minimum critical level filtering in winter at Rothera is likely to be a main cause for the winter enhanced GW-EP, as this would allow more orography-generated waves to reach the 30 to 45 km range. The stratospheric jet streams may also contribute to the winter enhancement at Rothera.

Responses of mesosphere and lower thermosphere temperatures to gravity wave forcing during stratospheric sudden warming

[1] We examine the responses of the mesosphere and lower thermosphere (MLT) temperatures to gravity waves (GWs) during stratospheric sudden warming (SSW) using TIME-GCM through modifying GW parameters. Our study confirms that the height of GW forcing region is mainly determined by GW amplitude and wavelength, and its vertical depth is closely tied to the spectral width of GW phase speed. The GW forcing controls the pattern and strength of residual circulation and thereby the characteristics of the MLT cooling and warming regions. The planetary wave (PW) forcing in the MLT also affects the vertical depth and magnitude of MLT temperature anomalies through further modifying the residual circulation. These PWs in MLT are likely generated in-situ by the GW forcing at high latitudes. Therefore, the mechanisms of GW controlling the MLT temperature during a SSW are directly through GW forcing and indirectly through generating PWs in-situ.

Field demonstration of simultaneous wind and temperaturemeasurements from 5to50 km with a Na double-edge magneto-optic filter in a multi-frequency Doppler lidar

We report the first (to our knowledge) field demonstration of simultaneous wind and temperature measurements with a Na double-edge magneto-optic filter implemented in the receiver of a three-frequency Na Doppler lidar. Reliable winds and temperatures were obtained in the altitude range of 10-45 km with 1 km resolution and 60 min integration under the conditions of 0.4 W lidar power and 75 cm telescope aperture. This edge filter with a multi-frequency lidar concept can be applied to other direct-detection Doppler lidars for profiling both wind and temperature simultaneously from the lower to the upper atmosphere.