The effect of convection scheme on tropical cyclones simulations over the CORDEX East Asia domain

Abstract

The effect of cumulus parameterization (CP) on simulated climatological tropical cyclone (TC) activity over the CORDEX East Asia domain has been investigated by using the weather research and forecasting model. The simulations were conducted during 1988–2009 with a 25-km horizontal resolution, driven by the ERA-Interim reanalysis. Five experiments were performed and evaluated with different CP schemes including Kain–Fritsch (KF), KF with modified convective trigger function (KFML), multi-scale KF (MsKF), simplified Arakawa–Schubert (SAS) and Betts–Miller–Janjic (BMJ) schemes. Significant differences of TC genesis locations and tracks can be found between the CP schemes, which are attributed to simulated large-scale environment discrepancies. Simulations with the KF, KFML and MsKF schemes produced more TC numbers and stronger intensities than the SAS and BMJ simulations. The eastward extension and enhancement of the monsoon trough (MT) in the KF, KFML and MsKF simulations caused a southeast shift of the main TC genesis region, and provided a suitable environment for TC development. The KFML simulation reduced the excessive rainfall and TC activities that had appeared in the KF simulation and increased the proportion of intense TCs. The reduced tropical surface latent and moisture flux in the MsKF simulation, along with weaker upward vertical motion, contributed to weaker tropical rainfall and TC intensities. The SAS simulation produced less large-scale instabilities, which led to less active convections and weaker TC genesis and intensities. The genesis region in the BMJ simulation was shifted further north due to the northward-shifted reverse-oriented MT together with enhanced wind shear over the tropical ocean, resulting in detrimental environmental conditions for TC development. In addition, the BMJ scheme produced significant upper-tropospheric warming, attributed to enhanced grid-scale convective heat transport and latent heating of condensation in high-level stratiform cloud extending to the south boundary of WPSH, this resulted in the retreat of the subtropical high and caused the TC to recurve earlier.