Nonmigrating diurnal tides observed in global thermospheric winds

Abstract

Nonmigrating diurnal tides between 90 and 270 km are inferred from Upper Atmosphere Research Satellite (UARS) wind imaging interferometer (WINDII) winds. This study represents the first known effort to directly analyze tidal wave number structure and propagation direction in winds observed over this altitude range. Prominent diurnal tides include an eastward propagating wave number 3, a zonally symmetric tide, and a westward propagating wave number 2. UARS High Resolution Doppler Imager winds between 60 and 100 km were analyzed identically and show excellent consistency with WINDII tides. Observed tides were compared with tidal fits to Hough Mode Extensions. WINDII tides are generally damped more slowly above 120 km than fitted tides, and the zonally symmetric tide indicates a thermospheric source not captured by Hough Mode Extensions. Our study provides additional confirmation that tides act as direct coupling agents between the troposphere and the thermosphere (and F region), in addition to their role in the E region dynamo. Key Points Presentation of observations of diurnal tides between 100-270 km Thermospheric nonmigrating tides have tropospheric and in-situ sources Observed thermospheric tides damp more slowly than modeled tides ©2013. American Geophysical Union. All Rights Reserved.