Analyzing The Spatiotemporal Diversity Of Westerly Wind Events In The Tropical Pacific

Observational analysis shows that Westerly Wind Events(WWEs)over the tropical Pacific are characterized by their spatiotemporal diversity.We can classify WWEs into six types based on their different locations and durations,the Western-Pacific(W)type of long(duration: 10–30 days)and short(duration: 6–10 days)events,the Central-Pacific(C)type of long and short events,the Eastern-Pacific(E)type of long and short events,respectively.The spatiotemporal characteristics of various types of WWEs are analyzed,including the amplitude and seasonal distributions,the horizontal and vertical structural evolutions,the related convective and circulation.The relationships between WWEs and MJO/CCKWs are further studied.The main conclusions are as follows:(1)Various types of WWEs exhibit quite different characteristics in terms of their amplitudes.The long events are stronger than the short events,and the maximum amplitudes of the C-type and E-type of long events are larger than the W-type of long ones.For the seasonal distributing characteristics of various types of WWEs,the population of WWEs tend to occur in the boreal winter in general and the details have differences.(2)The evolutions of these six types of WWEs are also quite different.The W-type short and long events and the C-type long events show a distinct eastward propagation,whereas the C-type short events and the E-type short and long events have no apparent propagation direction.We demonstrate that such a difference in the eastward propagation of WWEs can be significantly associated with the Madden-Julian Oscillation(MJO).(3)The W-type events(long and short events)and C-type long events are more closely associated with the MJO,especially for the W-type events,due to the regions and timescales.And they are influenced heavily by the MJO,as indicated by their more distinct eastward propagation patterns,than the C-type long events and the E-type events(long and short events).(4)In addition to the MJO,the convectively coupled Kelvin waves are also associated with the WWEs,especially for the short events.