Short-term variability and the weather of the day in the lower
thermosphere and ionosphere using a whole atmosphere model with upper
atmospheric observations
Abstract
Whole atmosphere models that fully capture the propagation of wave
dynamics from lower to upper atmosphere are believed sufficient to
reproduce the type of short-term variability in the neutral upper
atmosphere that produces observed variations in ionospheric parameters.
However, recent studies suggest that upper atmospheric observations are
needed to accurately represent short-term variability in both
planetary-scale mass transport and tidal behavior crucial to
representing the structure of the thermosphere and the wind-dynamo
coupling in the ionosphere. To address this, we use atmospheric
specifications from the prototype High-Altitude Navy Global
Environmental Model (HA-NAVGEM) from the ground to 92 km to nudge the
Whole Atmosphere Community Climate Model extended version (WACCM-X)
coupled to the Navy Highly Integrated Thermosphere Ionosphere
Demonstration System (Navy-HITIDES) ionospheric model. The HA-NAVGEM
data assimilation/forecast system is run in two configurations: a
reference experiment for the time period December 2012-March 2013, where
satellite-based middle atmospheric observations (SABER temperature
retrievals; Aura MLS temperature, ozone, and water vapor retrievals; and
SSMIS microwave radiances) are included between 20-90 km; and a
perturbed experiment, during the same time period, in which the middle
atmospheric observations are removed. The resulting nudged simulations
using WACCM-X coupled to Navy-HITIDES are used to study the impact of
upper atmospheric observations in reproducing the observed short-term
variability in the thermosphere-ionosphere system, both in terms of the
thermospheric structure and the ionospheric response via wind-dynamo
coupling. The role of solar thermal and lunar gravitational tides is
discussed, as well as the impact of observations on the weather of the
day in the lower thermosphere.