Impact of SSTA in the East Indian Ocean on the Frequency of Northwest Pacific Tropical Cyclones: A Regional Atmospheric Model Study

Abstract

The impact of the sea surface temperature anomaly (SSTA) in the East Indian Ocean (EIO) on the tropical cyclone (TC) frequency over the western North Pacific (WNP) and the involved physical mechanisms are examined using the International Pacific Research Center (IPRC) Regional Atmospheric Model (iRAM) driven by the reanalysis and the observed SSTs. The model reproduces generally quite realistic climatic features of the WNP TC activity, including the interannual variability of the WNP TC genesis frequency, the geographical distributions of TC genesis and frequency of occurrence. In particular, the model reproduces the observed statistical (negatively correlated) relationship between the WNP TC frequency and the EIO SSTA, as recently studied by Zhan et al.The experiments with artificially imposed SSTA in the EIO in the year 2004 with normal EIO SST and WNP TC activity confirm that the EIO SSTA does affect the TC genesis frequency in the entire genesis region over the WNP by significantly modulating both the western Pacific summer monsoon and the equatorial Kelvin wave activity over the western Pacific, two major large-scale dynamical controls of TC genesis over the WNP. Additional sensitivity experiments are performed for two extreme years: one (1994) with the highest and one (1998) with the lowest TC annual frequencies in the studied period. The results reveal that after the EIO SSTAs in the two extreme years are removed, the TC frequency in 1998 is close to the climatological mean, while the excessive TCs in 1994 are still simulated. The model results suggest that the warm EIO might be a major factor contributing to the unusually few TCs formed over the WNP in 1998, but the cold EIO seemed to contribute little to the excessive WNP TCs in 1994.

Indo-western Pacific ocean capacitor and coherent climate anomalies in post-ENSO summer: A review

“…These TC anomalies are captured in highresolution AGCM simulations, pointing to the importance of SST boundary conditions (Mei et al, 2015). Using a regional atmospheric model, Zhan et al (2011) showed that eastern IO SST anomalies affect TC genesis over the TNW Pacific by modulating the western Pacific summer monsoon via the equatorial Kelvin wave.…”

An Abrupt Decrease in the Late-Season Typhoon Activity over the Western North Pacific*

“…In the Atlantic, the upward trend in SST is highly correlated with the increase in the intensity of hurricane activity (Webster et al 2005;Emanuel 2005). Although the variability of typhoons is negatively correlated with the local SST (Chan 2006), the SST variations in both the tropical eastern Pacific (i.e., El Niño-Southern Oscillation) and Indian Ocean have been reported to play an important role in the interannual variability of TCs (e.g., Wang and Chan 2002;Camargo et al 2007;Zhan et al 2011;Du et al 2011). Recently, Jin et al (2013) showed that the off-equatorial SST warming over the central Pacific provides a favorable environment for TC motion toward East Asia during the central Pacific El Niño events.…”

On the weakened relationship between spring Arctic Oscillation and following summer tropical cyclone frequency over the western North Pacific: A comparison between 1968–1986 and 1989–2007

“…Thus, a better understanding of TC variability and its factors, and improved predictability of TC activity, are of great importance to society. It has been demonstrated that the TC variability over the western North Pacific (WNP) is significantly influenced by SST anomalies over the tropical central-eastern Pacific (e.g., Chan, 1985;Chen et al, 1998;Wang and Chan, 2002;Chan, 2005;Chen and Huang, 2008;Yeh et al, 2010;Cao et al, 2014a;Hsu et al, 2014) and over the Indian Ocean (Zhan et al, 2011). Studies have also indicated that atmospheric circulation systems can influence TC activity over the WNP, such as the stratospheric quasi-biennial oscillation (Chan, 1995;Ho et al, 2009), the Antarctic Oscillation (Ho et al, 2005), and the North Pacific Oscillation (Wang et al, 2007).…”