Diagnostic Analyses and Numerical Modeling of an Explosive Cyclone over the Northwestern Pacific on 11–13 January 2012

Explosive cyclone (EC), also known as a “meteorological bomb” for its rapid intensification (Rice, 1979), may potentially cause serious losses of life and property. Previous studies indicated that the Northwestern Pacific is one of the regions with most frequent occurrence of ECs in the world (Sanders and Gyakum, 1980; Yoshida and Asuma, 2004; Allen et al., 2010; Black and Pezza, 2013; Zhang et al, 2017). Sanders and Gyakum (1980) firstly defined EC as a cyclone whose central sea level pressure (SLP) decreased at an average rate of at least 1 hPa/h (Bergeron). The Kuroshio/Kuroshio Extension in the Northwestern Pacific provided favorable oceanic environmental conditions for EC occurrence (Chen et al., 1992; Yoshiike and Kawamura, 2009; Iizuka et al., 2013). An explosive cyclone occurred along the Kuroshio Extension over the Northwestern Pacific from 11 to 13 January 2012. In this study, the Final Analysis (FNL) data from National Centers for Environmental Prediction, as well as the Weather Research and Forecasting model (WRF-V3.5) were employed to simulate this EC. This cyclone generated in the east of Japan Islands around 18 UTC 10 January 2012. It deepened explosively from 00 UTC 11 to 18 UTC 12 January, and weakened near the Kamchatka Peninsula around 00 UTC 13 January. The FNL analyses showed that there was a distinct frontal structure. The high potential vorticity (PV) of the upper troposphere extended downward to the surface. The PV tower formed during the evolution of this EC.

In order to examine the development process of this cyclone in detail, we conducted a 54-h WRF simulation initialized at 18 UTC 10 January 2012. The change of sea surface temperature (SST) suggested that SST might affect the cyclone intensity significantly, but had little effect on the moving path of cyclone. The SST tests showed that warmer SST (SST+2K) might increase the cyclone intensity than that of control run, whereas cooler SST (SST-2K) might weaken the cyclone intensity. However, all WRF simulations exhibited much weaker trend of central pressure than that of FNL analysis. When turning off the latent heat release in the WRF modeling, the PV anomaly in the lower troposphere vanished. This result suggested that diabatic processes in the lower troposphere played an important role in the evolution of the EC.

Acknowledgement

This study is supported by the National Key R&D Program of China (2017YFC1404100，2017YFC1404101), and National Natural Science Foundation of China (41305086, 41775042, 41275049).

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