Accelerating two-stage explosive development of an extratropical cyclone over the northwestern Pacific Ocean: a piecewise potential vorticity diagnosis

Abstract

A B S T R A C T An extreme explosive extratropical cyclone over the northwestern Pacific Ocean (NPO) that formed in winter 2004 and went through two distinct rapid deepening periods was successfully simulated by a non-hydrostatic mesoscale model (MM5). Based on the simulation, the cyclone's rapid deepening was investigated in detail using the piecewise potential vorticity (PV) inversion method which successfully captured the characteristics of the cyclone and its associated background circulations. Results indicated that explosive development of the cyclone was dominated by forcings in the extended surface layer (ESL), which were closely related to baroclinity (temperature advection) and boundary layer processes (sensible heat exchange). In the interior layer (IL), direct effects of condensation were mainly conducive to the cyclone's development, whereas indirect effects (interactions with other layers) mainly acted conversely. Processes associated with latent heat release (LHR) were characterised by nonlinearity. Features of the precipitation, including intensity, duration, range and relative configuration to the cyclone determined the influences of condensation on the cyclone. In the upper layer (UL), tropopause-folding processes and horizontal PV advection were main influencing factors to the evolution of the cyclone. Upper-level forcings firstly exerted slight effects on the cyclone's development, since upper-level positive PV anomalies were far from the cyclone; then, as the influencing short-wave trough and the cyclone both moved northeastward, upper-level positive PV anomalies merged, enhanced and entered key areas of the cyclone, and thus both direct and indirect effects associated with the upper-level forcings strengthened significantly around the cyclone, and this dominated the cyclone's transition from a moderate explosive cyclone to an extreme one.

Investigating the Mechanisms Associated With the Evolutions of Twin Extratropical Cyclones Over the Northwest Pacific Ocean in Mid‐January 2011

“…A PV anomaly and its far field are different manifestations of the same phenomenon (Fu et al, 2014;Spengler & Egger, 2012). A PV anomaly and its far field are different manifestations of the same phenomenon (Fu et al, 2014;Spengler & Egger, 2012).…”

“…The EEC is an important subcategory of the extratropical cyclone that can develop rapidly (Sanders & Gyakum, 1980). Simulation studies based on various models found that latent heating (Davis et al, 1993;Kuwano-Yoshida & Asuma, 2008) and preexisting upper level disturbances (Fu et al, 2014;Hakim et al, 1996) were crucial for their rapid intensification. These pose serious threats to fishing and shipping industries.…”

“…Because of its proven ability to reproduce EECs effectively (Fu et al, 2014;Martin & Otkin, 2004;Parsons & Smith, 2004;Roebber & Schumann, 2011), the fifth-generation Pennsylvania State University National Center for Atmospheric Research Mesoscale Model (MM5, version 3.7) (Grell et al, 1995) was utilized in this study. MM5 is a limited-area, nonhydrostatic, terrain-following sigma-coordinate model designed to simulate/predict mesoscale and regional-scale atmospheric circulation.…”

Influential Role of Moisture Supply from the Kuroshio/Kuroshio Extension in the Rapid Development of an Extratropical Cyclone

“…We employed a conventional three-way partitioning of the PV anomalies (Korner and Martin 2000;Martin and Marsili 2002;Wu et al 2011;Fu et al 2014). In this method, the total PV perturbation field is separated into three layers.…”

“…Previous studies have pointed out that the development of explosive cyclones is influenced not only by baroclinic instability, but also by diabatic heating processes (e.g., Kuo et al 1991b;Reed et al 1993b;Yoshida and Asuma 2004;Kuwano-Yoshida and Asuma 2008;Fu et al 2014). Using numerical simulations, Kuo et al (1991b) revealed that latent heat release contributed to the intensification of an explosive cyclone over the northwestern Atlantic Ocean.…”