Future Directions for Whole Atmosphere Modeling: Developments in the Context of Space Weather Space Weather

Coupled Sun‐to‐Earth models represent a key part of the future development of space weather forecasting. With respect to predicting the state of the thermosphere and ionosphere, there has been a recent paradigm shift; it is now clear that any self‐respecting model of this region needs to include some representation of forcing from the lower atmosphere, as well as solar and geomagnetic forcing. Here we assess existing modeling capability and set out a road map for the important next steps needed to ensure further advances. These steps include a model verification strategy, analysis of the impact of nonhydrostatic dynamical cores, and a cost‐benefit analysis of model chemistry for weather and climate applications. Plain Language Summary Numerical models that comprehensively simulate the region between the Sun and the Earth represent a key part of the future development of space weather forecasting. With respect to predicting the Earth's upper atmosphere, there has been a recent paradigm shift; it is now clear that any self‐respecting model of this region needs to include some representation of impacts from below (the lower atmosphere) as well as from above (solar variability and the effects of solar wind fluctuations). Here we assess existing modeling capability and set out a road map for the important next steps needed to ensure further advances. These steps include a strategy for checking the accuracy of the models, an analysis of the impact of methods chosen to represent upper atmosphere dynamics, and an assessment of the relative benefits of comprehensive (but expensive) and simplified (but inexpensive) model representations of upper atmosphere chemistry.