Present Simulation and Future Typhoon Activity Projection over Western North Pacific and Taiwan/East Coast of China in 20-km HiRAM Climate Model

Abstract

A High Resolution Atmospheric Model (HiRAM) at 20-km resolution is adopted to simulate tropical storm (TS) activity over the western North Pacific (WNP) and Taiwan/East Coast of China (TWCN) at the present time (1979 -2003) and future climate (2075 -2099) under the Intergovernmental Panel on Climate Change (IPCC) fifth assessment report (AR5) representative concentration pathway (RCP) 8.5 scenarios. The results show that in contrast to TS simulation activities in most of the low-resolution climate models, TS activities except intensity over the WNP and TWCN region are well simulated by HiRAM at 20-km resolution. The linkage between large-scale environments and TS genesis simulated by HiRAM are dramatically superior to those in low-resolution fifth Coupled Model Intercomparison Project (CMIP5) models. During 2075 -2099, both TS genesis numbers and TS frequency over the WNP and TWCN are projected to decrease consistent with the IPCC AR5 report. However, the rate of decrease (49%) is much greater than that projected in IPCC AR5. The decrease in TC genesis numbers under global warming is primarily attributed to the reduction in mid-level relative humidity and large-scale ascending motion, despite the warmer sea surface temperature (SST) providing more favorable conditions for TS formation. TS intensity and the maximum precipitation rate are projected to increase under global warming. At the end of the 21 st century, the mean precipitation rate within 200 km of TS storm center over the TWCN region is projected to increase by 54%.

Simulation and Projection of Circulations Associated with Atmospheric Rivers along the North American Northeast Coast

“…The HiRAM has proved capable of realistically simulating rainfall distribution, snowfall in high mountains, extreme precipitation, and tropical cyclone activity partly because of its high resolution (Lau and Ploshay 2009;Freychet et al 2017a,b;Tsou et al 2016;Chen et al 2019). The model was used to conduct two time-slice experiments, which were driven by prescribed sea surface temperature (SST), in a manner similar to that in the study of Kusunoki and Mizuta (2013).…”

Impacts of Madden–Julian oscillation on tropical cyclone activity over the South China Sea: Observations versus HiRAM simulations

“…Using the same HiRAM framework but with a higher resolution (about 25 km), Tsou et al . (2016) successfully reproduced the historical TC activity over the western North Pacific. Kim et al .…”

“…Designed for global cloud‐resolving capability, HiRAM uses a nonintrusive shallow convective scheme (Bretherton et al ., 2004) and replaces the deep convective scheme by a six‐category bulk cloud microphysics scheme for the resolved component of cumulus convection processes (Zhao et al ., 2009). As a new member contributed to the upcoming CMIP6 (Coupled Model Intercomparison Project, phase 6), HiRAM has been used to study TC seasonal forecast over the North Atlantic (Zhao et al ., 2010; Chen and Lin, 2011) and eastern Pacific (Jiang et al ., 2012), as well as to project changes of TC activity over the western North Pacific (Tsou et al ., 2016) and changes of convection activity across the tropical Pacific under global warming (Bui et al ., 2019).…”

“…(2015) and Tsou et al . (2016) was adopted for detecting TC‐like vortices in model simulations. These criteria are listed as follows: At each 6‐hr time step, the detection scheme checks each grid point to find if the relative vorticity is greater than 1.5 × 10 −4 s −1 .…”

Preface to the Special Issue on “Climate Changes and Their Impacts in Taiwan”

“…(2) Constructing a multi-scalar drought index 1-km gridded dataset in Taiwan (Weng 2016). (3) Typhoon activities over the Western North Pacific Region (Tsou et al 2016).…”