ENSO and its Precursor simulated by UNICON with CESM1

Abstract:

Thanks to the convective momentum transport and the mass flux closure based on the diluted-CAPE, CESM1 drastically improves the simulation of the El Nino and Southern Oscillation (ENSO) phase over its precedent (i.e., CCSM3). However, the amplitude of ENSO simulated by CESM1 is too strong compared to that of the observation. This problem is remedied by a newly developed unified convection scheme, UNICON.

UNICON is a unified convection and a subgrid vertical transport scheme by nonlocal asymmetric turbulent eddies. UNICON simulates all dry-moist, forced-free, and shallow-deep convection within a single framework in a seamless, consistent and unified way. With a brief introduction of UNICON, it will be shown that UNICON implemented into CESM1 substantially improves the simulations of the diurnal cycle of precipitation, Madden-Julian Oscillation (MJO), and tropical cyclones, all of which have been notoriously difficult to simulate by the most of GCMs. Finally, ENSO and its precursor simulated by UNICON will be compared with the default CESM1 and the observation.