Future Changes in Tropical Cyclone Activity Projected by HiRAM-SIT
Abstract
HiRAM, the GFDL global HIgh Resolution Atmospheric Model, and HiRAM coupled with SIT (Snow/Ice/Thermocline) single column ocean model were used for climate experiments following HighResMIP protocols. In the Tier 1 experiment HiRAM well simulates mean climatology, seasonal evolution of Asian Monsoon, frontal activity, and tropical cyclone-intraseasonal oscillation relationship. Strength of simulated extreme precipitation is compatible with TRMM precipitation. In the Tier 2 historical experiment HiRAM-SIT produces similar climatology as HiRAM, but better diurnal cycle of precipitation, near surface temperature and MJO eastward propagation. Due to the lack of ocean circulation in the HiRAM-SIT coupled model, simulated 0.25-deg SST were nudged to HadISST2.2 in the Tier 2 historical (1950-2014) experiment to avoid climate drift. Same nudging method was applied with SST from HighResMIP-futureSSTSeaice in the Tier 2 future (2015-2050) experiments.
It is noticed that tropical cyclone activity in the western North Pacific is projected to be significantly weakened in the Tier 2 future experiments. This is due to the equatorward contraction of convection and the corresponding anomalous subsidence poleward of the equatorial convection belt. Strongest response occurs in the western North Pacific and results in significantly weakened convection and westward extension of the subtropical anticyclone. Vorticity budget analysis finds that the background state decides the amplitude of response. The anticyclonic response is the largest in this monsoon trough (cyclonic) region. This is true even if the low-level divergence anomaly is zonally symmetric. Dynamical Interaction between vorticity and divergence anomalies, the associated thermodynamic components, and the dynamical-thermodynamic interaction likely further enhance the response in the monsoon trough and cyclonic regions.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A11Q2739T
- Keywords:
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- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1627 Coupled models of the climate system;
- GLOBAL CHANGE;
- 1655 Water cycles;
- GLOBAL CHANGE