The Variabilities of the Mesosphere and Lower Thermosphere as observed by TIMED

The Mesosphere and Lower Thermosphere (MLT) is a region of the Earth atmosphere that is very sensitive to external influences from the sun above and lower atmosphere below it. Its chemical, momentum and thermal balance, thus basic states (i.e. pressure, density, and temperature, and winds) can change in different time scales due to naturally-occurring and/or human-induced changes to the composition and energy contained within this region. The NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) mission, since its successful launch in December 2001, has provided for the first time a comprehensive view of the basic structure and its variabilities of the MLT system during the descreasing phase of this current solar cycle. This paper gives a 5-year climatological view of the MLT system as observed by the TIMED spacecraft and reports the characteristics and magnitudes of its temporal and spatial variabilities. Examples of the observed climatology and variabilities will be used to examine and assess our basic understanding of coupled radiative/chemical/dynamical processes that occur in the system.