Development and Validation of the Whole Atmosphere Community Climate Model With Thermosphere and Ionosphere Extension (WACCM‐X 2.0)

Abstract

Key developments have been made to the NCAR Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM‐X). Among them, the most important are the self‐consistent solution of global electrodynamics, and transport of O+ in the F‐region. Other ionosphere developments include time‐dependent solution of electron/ion temperatures, metastable O+ chemistry, and high‐cadence solar EUV capability. Additional developments of the thermospheric components are improvements to the momentum and energy equation solvers to account for variable mean molecular mass and specific heat, a new divergence damping scheme, and cooling by O(3P) fine structure. Simulations using this new version of WACCM‐X (2.0) have been carried out for solar maximum and minimum conditions. Thermospheric composition, density, and temperatures are in general agreement with measurements and empirical models, including the equatorial mass density anomaly and the midnight density maximum. The amplitudes and seasonal variations of atmospheric tides in the mesosphere and lower thermosphere are in good agreement with observations. Although global mean thermospheric densities are comparable with observations of the annual variation, they lack a clear semiannual variation. In the ionosphere, the low‐latitude E × B drifts agree well with observations in their magnitudes, local time dependence, seasonal, and solar activity variations. The prereversal enhancement in the equatorial region, which is associated with ionospheric irregularities, displays patterns of longitudinal and seasonal variation that are similar to observations. Ionospheric density from the model simulations reproduces the equatorial ionosphere anomaly structures and is in general agreement with observations. The model simulations also capture important ionospheric features during storms.

Height Variation of Gaps in 150‐km Echoes and Whole Atmosphere Community Climate Model Electron Densities Suggest Link to Upper Hybrid Resonance

“…Our findings are supported by simultaneous observations with the Vertical Incidence Pulsed Ionosphere Radar (VIPIR, an advanced ionosonde-dynasonde system) (Bullett et al, 2010) and by comparison of gap heights with electron density contours calculated with the WACCM-X 2.0 global atmosphere and ionosphere model (Liu et al, 2018). Our findings are supported by simultaneous observations with the Vertical Incidence Pulsed Ionosphere Radar (VIPIR, an advanced ionosonde-dynasonde system) (Bullett et al, 2010) and by comparison of gap heights with electron density contours calculated with the WACCM-X 2.0 global atmosphere and ionosphere model (Liu et al, 2018).…”

The Effects of Vertically Propagating Tides on the Mean Dynamical Structure of the Lower Thermosphere

“…However, one would expect different qualitative and quantitative results (e.g., Yigit et al, 2009) if this same study was performed with a model that included a gravity wave parameterization (e.g., the whole atmosphere community climate model with thermosphere and ionosphere extension, WACCM-X; Liu et al, 2018). Therefore, the results presented herein highlight exclusively the effects of vertically propagating tides on the zonal-mean zonal wind balance in the lower thermosphere.…”

The Influence of Internal Atmospheric Variability on the Ionosphere Response to a Geomagnetic Storm

“…The simulations performed in the present study use WACCM-X version 2.0 (Liu et al, 2018), which is part of the National Center for Atmospheric Research Community Earth System Model. WACCM-X extends from the surface to the upper thermosphere (4.1 × 10 −10 hPa, ∼500-700 km).…”

“…WACCM-X extends from the surface to the upper thermosphere (4.1 × 10 −10 hPa, ∼500-700 km). As discussed in Liu et al (2018), WACCM-X version 2.0 incorporates additional thermosphere and ionosphere processes in order to model the upper atmosphere. The chemical, dynamical, and physical processes in the troposphere, stratosphere, and mesosphere are based on the Whole Atmosphere Community Climate Model (WACCM) version 4 (Marsh et al, 2013), which itself is based on the Community Atmosphere Model version 4 (Neale et al, 2013).…”

“…The model horizontal resolution is 1.9 ∘ in latitude and 2.5 ∘ in longitude, and the vertical resolution is 0.25 scale heights in the upper atmosphere. The reader is referred to Liu et al (2018) for a detailed description of WACCM-X version 2.0. As discussed in Liu et al (2018), WACCM-X version 2.0 incorporates additional thermosphere and ionosphere processes in order to model the upper atmosphere.…”