Usually in perturbation GCM experiments of this kind that impose a large climate perturbation on a Earth-like climate restart file, the first few months of the experiment are discarded as a spinup period and the climatology is then analysed. Instead, here we examine the spinup period as giving insights into the development of the tropical cyclone world from an initial state of an Earth-like climate. Upon the removal of all topography and the imposition of a tropical SST globally, mid-latitude cyclones provide a source of convection that initiates the development of tropical cyclones in the mid-latitudes and polar regions of the aquaplanet. Within two weeks, mid-latitude cyclones are completely converted into tropical cyclones. This is easily recognized by the generation in mid-latitude and polar regions of symmetric storms of considerably smaller size than the asymmetric mid-latitude cyclones, and with central pressures as low as 940 hPa. In this experiment, tropical cyclones continue to form in tropical latitudes and drift poleward but their numbers are dwarfed by the mid-latitude and polar “tropical” cyclones.
This aquaplanet simulation is then run for a period of 10 years and the simulated climatology of tropical cyclones is examined. Results from this simulation will be presented at the conference, along with an examination of how these model results can be used to inform a climate theory of tropical cyclone formation.
Bi, D., Dix, M., Marsland, S. J., O’Farrell, S., Rashid, H., Uotila, P., ... & Yan, H. (2013). The ACCESS coupled model: description, control climate and evaluation. Aust. Meteorol. Oceanogr. J, 63(1), 41-64.
Hayashi, Y. Y., & Sumi, A. (1986). The 30-40 day oscillations simulated in an "aqua planet" model. J. Meteor. Soc. Japan, 64(4), 451-467.
Hardiman, S. C., Boutle, I. A., Bushell, A. C., Butchart, N., Cullen, M. J., Field, P. R., ... & O’Connor, F. M. (2015). Processes controlling tropical tropopause temperature and stratospheric water vapor in climate models. J. Climate, 28(16), 6516-6535.
Khairoutdinov, M., & Emanuel, K. (2013). Rotating radiative‐convective equilibrium simulated by a cloud‐resolving model. J. Adv. Model. Earth Sys., 5(4), 816-825.
Reed, K. A., & Chavas, D. R. (2015). Uniformly rotating global radiative‐convective equilibrium in the Community Atmosphere Model, version 5. J. Adv. Model. Earth Sys, 7(4), 1938-1955.