Comparisons of Two Types of El Niño Impacts on TC Genesis over the South China Sea

Abstract

This chapter examines the impacts of warm pool (WP) El Nino on the tropical cyclone (TC) genesis over the South China Sea (SCS) during 1965–2004. We check the relationships between WP El Nino and SCS TC genesis in Sept-Oct-Nov (SON) when the interannual variability of TC genesis is significant. Compared with the cold tongue (CT) El Nino, the relationship of TC genesis with WP El Nino is significant. In recent a couple of decades with more frequent WP El Nino, the significant coherent variations between TC genesis and WP NINO index on the timescales of approximately 4 years are displayed. The distinct different atmospheric teleconnection patterns related to CT and WP El Nino are responsible for these relationships. The WP El Nino could result in a dipolar pattern with anticyclone anomalies over the SCS and cyclone anomalies over the western tropical Pacific warm pool at low- and mid-level, which is different from the CT El Nino-induced anticyclone anomalies over the SCS and western tropical Pacific warm pool. These WP El Nino-related large-scale circulation anomalies could enlarge the low-level northerlies over the SCS, which consequently enhances the vertical wind shear and suppresses the TC genesis over the SCS.