Exploring the effects of a nonhydrostatic dynamical core in high‐resolution aquaplanet simulations

Abstract

This study explores the impact of a nonhydrostatic dynamical core in high‐resolution regional climate simulations using an aquaplanet framework. The Weather Research and Forecasting (WRF) model is used to conduct simulations with both hydrostatic (H) and nonhydrostatic (NH) solvers at horizontal grid spacings (Δx) of 36, 12, and 4 km. The differences between the H and NH simulated precipitation (ΔP) are notable even at Δx = 12 km in the intertropical convergence zone and the transition region to the drier subtropics. At gray zone grid spacing (12 km and 4 km) over the tropics, ΔP is sensitive to whether a cumulus parameterization scheme is used or not. With an idealized Witch of Agnesi land mountain, differences in the precipitation and circulation (vertical velocity) between the H and NH simulations are significant even at Δx = 36 km in the tropics due largely to the strong feedbacks related to moist processes. The differences increase as the model grid spacing and mountain half width (a) are reduced, accompanied by a shift toward a more nonhydrostatic flow regime at a = 24 km. Latent heat release drastically enhances the differences between the NH and H simulations and extends the effect of nonhydrostatic dynamics to a broader region over the mountain and downstream over the tropics. Overall, differences exist between H and NH simulations even at resolutions between 12 and 36 km, but the differences are sensitive to the representations of moist physics and other features such as horizontal diffusion used in the WRF model.

Sensitivity of U.S. summer precipitation to model resolution and convective parameterizations across gray zone resolutions

“…Also, consistent with Yang et al . [] who noted the importance of physics‐dynamics interactions in amplifying the difference between simulations with hydrostatic versus nonhydrostatic dynamical cores, our results show larger differences between H and NH at 36 km and 12 km resolution with the KF scheme compared to 4 km resolution without a cumulus scheme.…”

“…Consistent with Lebassi‐Habtezion and Diffenbaugh [] and Yang et al . [], nonhydrostatic dynamics has a positive impact on precipitation simulations over the western U.S. with complex terrain even at 12 km and 36 km grid spacings. The smaller differences between simulations with the hydrostatic versus nonhydrostatic dynamical core in this study compared to those in Lebassi‐Habtezion and Diffenbaugh [] are likely related to the different emphases on precipitation in the warm versus cold seasons.…”

“…More specifically, nonhydrostatic dynamics may produce noticeable improvement in simulating orographic precipitation [ Janjić et al ., ]. As dynamics interact with the moist physics, the impacts of using H versus NH dynamical cores could be non‐negligible even at mesoscale resolutions [ Yang et al ., ]. Additional simulations performed by using spectral nudging are also used to further explore the relative impacts of large‐scale circulation biases on simulations of precipitation.…”

Sensitivity of Mountain Hydroclimate Simulations in Variable‐Resolution CESM to Microphysics and Horizontal Resolution

“…Nonetheless, at increasingly finer grid‐spacing, hydrostatic models have been shown to exhibit divergent growth in the vertical velocity compared with nonhydrostatic models (Jeevanjee, ; Morrison, ; Weisman et al, ). Recent analyses by Yang et al () using both hydrostatic and nonhydrostatic formulations of the Weather Research and Forecasting (WRF) model at 36, 12, and 4 km showed statistically significant differences in simulated total precipitation in the tropics (largely due to latent heat release). However, differences within the midlatitudes were negligible between nonhydrostatic and hydrostatic simulations.…”

Impact of Atmospheric Rivers on Surface Hydrological Processes in Western U.S. Watersheds

“…Previous studies have mostly been conducted to either focus on fine spatial resolution over short durations or long duration at a coarse resolution (Chen & Hossain, ; Hu et al, ; Leung & Qian, ). With advances in computing resources, convection permitting climate simulations at grid spacing of a few kilometers are becoming feasible and recent studies have demonstrated their usefulness for simulating cold season orographic precipitation and snowpack dynamics (Rasmussen et al, ) and extreme precipitation (Liu et al, ; Prein et al, ) as well as warm season precipitation and its diurnal variability (Gao et al, ; Prein et al, ; Yang et al, ). Overcoming the limitations of both model resolution and simulation period opens the door to improving analysis of AR events on climate time scale.…”