Influence of Climate Regime Shift on the Abrupt Change of Tropical Cyclone Activity in Various Genesis Regions

In this chapter, we reported the effect of basin-scale climate regime shift (CRS) on the abrupt change of tropical cyclone (TC) activity in various genesis basins, including the Pacific, Atlantic, and Indian Oceans. An analysis of regime shift index reveals that the worldwide TC activity experienced four significant abrupt changes during 1960–2014, including (i) an abrupt increase/decrease in the eastern North Pacific (ENP)/western North Pacific (WNP) in the early 1970s, (ii) an abrupt increase in the ENP and WNP in the early 1980s, (iii) an abrupt increase in the North Atlantic and ENP in the middle 1990s, and (iv) an abrupt decrease in the WNP and western South Pacific in the late 1990s. Three of them are identified concurrent with a significant CRS. The possible influence of a CRS on the abrupt change of TC activity in various genesis regions is addressed. We demonstrate that a CRS induced time mean state shift results in a rapid change in the large-scale dynamic and thermodynamic conditions, which substantially contributes to the abrupt change of TC activity in various genesis regions. In addition the CRS, the effect of interdecadal variability, such as the interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation, on the abrupt change of TC activity was discussed

A Study of East Asian Cold Surges during the 2004/05 Winter: Impact of East Asian Jet Stream and Subtropical Upper-Level Rossby Wave Trains

Cold surges were unusually active in subtropical East Asia during January - February 2005. These cold surges were pre ceded by up stream wave trains, which originated in the Mediterranean-Sahara region and prop a gated east ward along the sub tropical jet stream over the Eurasian continent. The northerly of the upper-level cyclonic anomaly in East Asia coupled with the low-level northerly upon the arrival of wave activity, and this was followed by a quick south ward penetration of cold air mass and surface anticyclone. Diagnostic and numerical results suggest that the anomalously active wave activity affecting the East Asian cold surges may be attributed to an anomalously enhanced jet stream over the Middle East and an anomalously west ward extension of the East Asian Jet Stream. The configuration of these two subtropical jet streams established a strong wave guide through which wave activity forced in the Mediterranean-Sahara region could efficiently prop a gate to East Asia, resulting in above aver age cold surge events in subtropical East Asia. Wave-like perturbation tended to be amplified at the entrance to the East Asian jet through barotropic energy conversion from the mean flow