Two Types of the East Asian Cold Surge and Their Impacts on El Niño

Abstract

Abstract Case studies have shown that the East Asian cold surge (CS) in winter exerts considerable impact on the development of El Niño by changing the surface wind over the western equatorial Pacific. However, a statistical assessment of the conditions under which the CS is more likely to make such an impact is lacking. Our statistical analysis shows that the CS can be divided into two types with respect to their prevailing area. The western CS type passing through the South China Sea rarely influences the equatorial surface wind owing to blocking and friction effects from high mountains in Borneo, whereas the eastern CS type passing through the Philippine Sea induces strong equatorial surface westerly anomalies. Observations and model experiments show that only the eastern CS type can efficiently trigger El Niño.