Abstract
In this study, we examine the tropical cyclone (TC) activity over the western North Pacific (WNP) in 2018–2020 and its relationship with planetary scale convection and circulation anomalies, which play an important role for TC genesis. To determine the sea surface temperature (SST)-forced atmospheric variability, atmospheric general circulation model (AGCM) ensemble simulations are executed along with the observed SST. For AGCM experiments, we use two different convection schemes to examine uncertainty in convective parameterization and robustness of simulated atmospheric response. The observed TC activity and genesis potential demonstrated consistent features. In our AGCM ensemble simulations, the updated convection scheme improves the simulation ability of observed genesis potential as well as planetary scale convection and circulation features, e.g., in September–October–November (SON), a considerable increase in the genesis potential index over the WNP in SON 2018, WNP in SON 2019, and South China Sea (SCS) in SON 2020, which were not captured in the Emanuel scheme, have been simulated in the updated convection scheme.
Highlights
Tropical cyclones (TCs) are important extreme weather events that has a socioeconomic impact on populated areas through strong winds and heavy precipitation
Ogata et al (2021) demonstrated that using the Emanuel scheme AFES, TCF variability is simulated in JJA but not in SON
They concluded that this difference is attributed to the internal atmospheric variability
Summary
Tropical cyclones (TCs) are important extreme weather events that has a socioeconomic impact on populated areas through strong winds and heavy precipitation. The observed TCF decrease over the WNP during JJA 2020 is significantly related (simulated as SST-forced response) to the central equatorial cold Pacific SST anomalies (Figure 6C) using the GPI decrease by the anticyclonic vorticity In both AFES simulations, the anticyclonic circulation observed over the WNP (Figure 4C) was not simulated, which indicates the underestimation of the atmospheric response to basin warming over the Indian Ocean (Xie et al, 2009; Du et al, 2011). Over the SCS, the anticyclonic response decay by the Indian Ocean basin warming in SON (e.g., Ueda et al, 2018) may help the favorable TC genesis in SON 2020
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