Influence of a spectral cumulus parametrization on simulating global tropical cyclone activity in an AGCM

Abstract

AbstractThe influence of a new spectral cumulus parametrization (the spectral scheme) on simulating global tropical cyclone (TC) activity in an Atmospheric General Circulation Model (AGCM) is investigated. Experiments are performed using AFES (AGCM for the Earth Simulator) and two different convection schemes – the original convection scheme of the AGCM (the Emanuel scheme) and the spectral scheme. The result shows that the both schemes can capture qualitative features of global TC activity in terms of climatology, variability, and intensity. However, the spectral scheme simulates TC genesis and track density better than the original convection scheme by improving the cold bias in the upper troposphere. The spectral scheme also provides better results for TC response to interannual variability (i.e., El Niño Southern Oscillation, ENSO) by suppressing excessive convection response to ENSO. The spectral scheme is capable of simulating the variability of TC genesis related to the Madden–Julian Oscillation (MJO) much better than the original convection scheme. Consequently, the spectral scheme can outperform the original convection scheme in simulating global TC activity from various perspectives, and thus the scheme is expected to be useful for TC prediction and future projections.