Research about the nontraditional Coriolis terms
Zonal temporal dispersion relations of the equatorially confined wave solutions with (black) and without (red) the nontraditional Coriolis terms (NCTs). Except the last frame of the animation, sound of piano is played at a sound frequency proportional to the effective buoyancy frequency used to plot every frame. (From Ong and Roundy 2020)
NCTs represent components of Coriolis force that turn eastward motion upward and upward motion westward, and vice versa.
NCTs, long neglected in global atmospheric models, significantly influence tropical circulation. Over the past years, I have uncovered several dynamic pathways through which NCTs alter the tropical circulation. I am leading a cross-institutional project to incorporate NCTs into CESM3 and E3SM using two nonhydrostatic dynamical cores, Spectral Element and MPAS (Skamarock, Ong, and Klemp, 2021). Our results suggest that omitting NCTs can be a contributor to the long-standing double intertropical convergence zone (ITCZ) bias in models.
The above figure outlines a model hierarchy for NCT effects on tropical flow.
The NCTs effectively make westward-moving air mass heavier and eastward-moving one lighter (White & Bromley, 1995; Ong & Roundy, 2020a).
The NCTs make large-scale eastward-propagating waves or convective systems faster and westward ones slower (Gilman & Glatzmeier, 1981; Verhoeven & Stellmach, 2014; Ong & Roundy, 2020b; Ong & Yang, 2022).
Because of the NCTs, mixed planetary-compressional Rossby waves exist (Bekki et al., 2022; Ong & Yang, 2025).
The NCTs induce westward acceleration in diabatic heating regions, either large-scale (Hayashi & Itoh, 2012; Ong & Roundy, 2019) or convective-scale (Brown & Ahlers, 2007; Igel & Biello, 2020; Marsico et al., 2023). This effect can further concentrate tropical precipitation towards the equator in climate models (Ong et al., ongoing).
The NCTs can influence multiscale interactions, including upscale effects (Coleman et al., 1990; Brown & Ahlers, 2007; Verhoeven & Stellmach, 2014; Goldsmith et al., 2025) and downscale effects (Zikanov et al., 2003; McWilliams & Huckle, 2006).
Due to the NCT effects on multiscale interaction, the planetary boundary layer tends to be deeper with easterly winds and shallower with westerly winds, and these effects can further support and suppress, respectively, trade-wind shallow convection and can be modeled with large-eddy simulations (Ong, 2026, preprint) and CLUBB parameterization (Ong & Larson, 2026)