Impact Of Seasonal Variation On Interannual Scale Air-sea Coupling Events In Indian Ocean

The seasonal variation of the sea surface temperature in the Indian Ocean is characterized by complex multi-modal.Each mode in different regions has its own characteristic of seasonal phase-locking.For example,the tropical Indian Ocean Dipole(IOD)achieves the peak in spring;the Ningaloo Ni?o occurred in Northwestern Australian achieves the peak in summer;the Subtropical Indian Ocean Dipole(SIOD)achieves the peak in autumn.So far,the physical mechanism of the complex temporal and spatial characteristics of climate models mentioned above is an important scientific problem that has not been solved.On the basis of previous works,we attempt to reveal the spatial and temporal variations of the above modes from modulation of seasonal cycle to interannual variation,the following new understandings are obtained:(1)Presents an innovative dynamic and thermal framework for the interannual variation of the seasonal cycle of Indian Ocean.The mechanism of how to establish seasonal phase-locking and spatial distribution of IOD,Ningaloo Ni?o and SIOD has been revealed from the interaction of the background field and the perturbed field.The result shows that,their development(attenuation)is realized by strengthening(weakening)the background field and the disturbance field.The main dynamic and thermal coupling mechanism is the feedback of “Wind-evaporation-SST”.But the unique climate combination of trade winds and monsoon demarcated by 10°S in the Indian Ocean is the root cause of the spatial variation of the above modes.(2)Discusses the physical essential of the tripole mode in South Indian Ocean.The South Indian Ocean tripole mode found in the southern Indian Ocean with EOF analysis of sea surface temperature data actually reflects the evolution of Ningaloo Nino to SIOD in different seasons,and is not an independent physical mode.This analysis is also beneficial to enhance the understanding of the relationship between different modes of Indian Ocean.