Simulations of the Present and Late-Twenty-First-Century Western North Pacific Tropical Cyclone Activity Using a Regional Model

Abstract

A high-resolution regional atmospheric model is used to simulate present-day western North Pacific (WNP) tropical cyclone (TC) activity and to investigate the projected changes for the late twenty-first century. Compared to observations, the model can realistically simulate many basic features of the WNP TC activity climatology, such as the TC genesis location, track, and lifetime. A number of spatial and temporal features of observed TC interannual variability are captured, although observed variations in basinwide TC number are not. A relatively well-simulated feature is the contrast of years when the Asian summer monsoon trough extends eastward (retreats westward), more (fewer) TCs form within the southeastern quadrant of the WNP, and the corresponding TC activity is above (below) normal over most parts of the WNP east of 125°E. Future projections with the Coupled Model Intercomparison Project phase 3 (CMIP3) A1B scenario show a weak tendency for decreases in the number of WNP TCs, and for increases in the more intense TCs; these simulated changes are significant at the 80% level. The present-day simulation of intensity is limited to storms of intensity less than about 55 m s−1. There is also a weak (80% significance level) tendency for projected WNP TC activity to shift poleward under global warming. A regional-scale feature is a projected increase of the TC activity north of Taiwan, which would imply an increase in TCs making landfall in north China, the Korean Peninsula, and parts of Japan. However, given the weak statistical significance found for the simulated changes, an assessment of the robustness of such regional-scale projections will require further study.

Past and Projected Changes in Western North Pacific Tropical Cyclone Exposure

“…A number of previous studies have explored relationships between WNP TC track characteristics and anthropogenic climate change and have identified systematic shifts in TC genesis location and steering flow that combine to cause TC track shifts (Wu and Wang 2004;Li et al 2010;Wang et al 2011;Murakami et al 2011Murakami et al , 2012Yokoi et al 2013;Bell et al 2013;Mori et al 2013;Manganello et al 2014;Wu et al 2014;Colbert et al 2015;Mei et al 2014Mei et al , 2015Roberts et al 2015;Wang and Wu 2015). There is, however, some divergence among the model projections in some of these studies.…”

“…There is, however, some divergence among the model projections in some of these studies. While some high-resolution climate models (usually forced with fixed sea surface temperature) show a poleward shift that is generally attributed to the expansion of the tropics (e.g., Murakami et al 2012;Wu et al 2014), other modeling studies emphasize an eastward shift of the TC tracks toward the central Pacific (Li et al 2010;Murakami et al 2011;Yokoi et al 2013;Mori et al 2013). In some cases, northward and eastward shifts occur FIG.…”

Changes in intense tropical cyclone activity for the western North Pacific during the last decades derived from a regional climate model simulation

“…A number of studies demonstrated high skill of atmospheric regional climate models (RCMs) to downscale meso-scale features of TCs (Feser and von Storch 2008a, b;Walsh et al 2004;Knutson et al 2007;Wu et al 2014;AuYeung and Chan 2012;Huang and Chan 2014). Although simulated TC intensities are often too small compared to observed values, they are still more realistic than those in global reanalyses.…”

“…Knutson et al (2007) showed that dynamical downscaling of NCEP atmospheric reanalyses with an 18-km grid RCM utilizing spectral nudging, successfully reproduces the observed interannual TC variability over the North Atlantic basin between 1980 and 2006. Wu et al (2014) followed the approach of Knutson 2007 for the western North Pacific. But the authors were not able to reproduce the interannual variability of TC activity, mostly due to a weak/absent relationship with ENSO (Camargo et al 2007;Wang and Chan 2002).…”

Projected Twenty-First-Century Changes in the Length of the Tropical Cyclone Season

“…Furthermore, other CMIP5 analyses (Camargo 2013;Tory et al 2013;Murakami et al 2014) project a reduction of global TC frequency by the end of the twentyfirst century for most models. Regional changes in TC frequency are more uncertain (e.g., Knutson et al 2008;Villarini andVecchi 2012, 2013;Knutson et al 2013;Wu et al 2014). …”