Simulations of the effects of vertical transport on the thermosphere and ionosphere using two coupled models

Abstract

(2014), Simulations of the effects of vertical transport on the thermosphere and ionosphere using two coupled models, J. Geophys. Res. Space Physics, 119, 1172-1185, doi:10.1002 AbstractWe have explored the sensitivity of the thermosphere and ionosphere to dynamical forcing from altitudes near the mesopause (∼95 km). We performed five simulations, all for the year 2009, with the National Center for Atmospheric Research (NCAR)/Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM). Two simulations were driven with the NCAR Global Scale Wind Model, and three used output from the Advanced Level Physics High Altitude (ALPHA) version of the Navy's Operational Global Atmospheric Prediction System (NOGAPS). Use of NOGAPS-ALPHA allows for realistic meteorological variability from the lower atmosphere to propagate up into the TIEGCM, including a rich spectrum of nonmigrating tides. We find that the additional vertical transport from these tides causes a significant reduction in the calculated peak electron density of the ionospheric F 2 layer (NmF2). The mechanism for this effect is the enhanced downward transport of atomic oxygen to the base of the thermosphere. In turn, this yields a greater relative abundance of N 2 and hence enhanced recombination of ions and electrons. To get improved agreement with observed electron densities, we must reduce (K zz ) by a factor of 5. However, even with lower K zz , our calculation still underestimates the NmF2 compared with radio occultation observations by the Constellation Observing System for Meteorology, Ionosphere and Climate satellite system. This underestimate of NmF2 may be linked to an overestimate of the nonmigrating tides in the coupled TIEGCM-NOGAPS calculations or to uncertainties in the bottom boundary for atomic oxygen in the TIEGCM.

Evaluating Different Techniques for Constraining Lower Atmospheric Variability in an Upper Atmosphere General Circulation Model: A Case Study During the 2010 Sudden Stratospheric Warming

“…This follows from the concepts also employed by the mesoscale modeling community whereby a time ramp is used to avoid shocking the model physics, which can occur when constraining to observations too quickly. Following the conclusions of Siskind et al () and to be consistent with prior TIME‐GCM simulations performed by J. C. Wang et al (), the eddy diffusion coefficient ( K z z ) in all our TIME‐GCM simulations was reduced by a factor of 10 (i.e., approximately an order of magnitude lower than the global average values reported by Jones et al, ) in order to compensate for the increased mixing downward transport introduced by including realistic wave perturbations from NAVGEM‐HA.…”

“…Four‐dimensional Tendency nudging (originally called 4D DA by Stauffer & Seaman, , , and references therein) was developed for tropospheric mesoscale weather prediction and was applied to the TI system by Siskind and Drob () and Siskind et al (). Conceptually, 4D Tendency nudging dynamically adjusts model horizontal winds and temperatures to reanalysis data (or observations in the case of DA) by adding an artificial source term to the prognostic zonal, meridional, and thermodynamic energy equations.…”

“…Here α is equal to 1 in both the SD zm and SD full TIME‐GCM simulations resulting in a model relaxation time of 30 s. The 4D Tend simulation is representative of the 4D Tendency nudging approach, where TIME‐GCM zonal mean and wave perturbations in horizontal winds and neutral temperatures are relaxed to 3‐hourly NAVGEM‐HA fields in the middle atmosphere via equation . For the 4D Tend case, G is chosen to be 1.5 × 10 −4 s −1 , corresponding to a relaxation time of ∼1.85 hr (after Siskind & Drob, ; Siskind et al, ). Additionally, we performed a standard/driven TIME‐GCM simulation for reference, driven solely at the lower boundary by daily varying background fields from ECMWF reanalysis data and climatological migrating and nonmigrating diurnal and semidiurnal tidal perturbations the GSWM version 2009 (Zhang et al, , ).…”

“…A somewhat different nudging approach was used by Siskind and Drob () and Siskind et al () to investigate how nonmigrating tides affect the vertical transport of light constituents in the TI. They employed a nudging technique in the NCAR thermosphere‐ionosphere‐electrodynamics general circulation model (TIE‐GCM) pioneered by the mesoscale modeling community (cf., Stauffer & Seaman, , ).…”

Comparison of co‐located independent ground‐based middle atmospheric wind and temperature measurements with numerical weather prediction models

“…For several reasons, there is an increasing interest to develop coupled whole atmosphere models that extend from the ground to the thermosphere [e.g., Siskind et al, 2014]. First, as mentioned it is now recognized that improvements in the middle and upper atmospheric regions can improve tropospheric forecast skill scores [e.g., Sigmond et al, 2013].…”