Contrasting the evolution of moderate and extreme positive Indian Ocean Dipole events

International Conference On Tropical Meteorology And Atmospheric Sciences

生态环境科学;原子能学

Hermawanto, A.^1^2 ; Wu, Lixin^1 ; Mamenun^2

Physical Oceanography Laboratory/CIMST, Ocean University of China, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China^1

Center for Applied Climate, Indonesia Agency for Meteorology Climatology and Geophysics (BMKG), Jakarta, Indonesia^2

关键词: Composite analysis;    Equatorial Indian Ocean;    Heat budget analysis;    Indian Ocean dipole;    pIOD;    Sea surface temperature (SST);    Temporal and spatial evolutions;    Wind anomalies;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/303/1/012001/pdf
DOI  :  10.1088/1755-1315/303/1/012001

学科分类：环境科学（综合）

来源: IOP

【 摘 要 】

A recent study suggested, due to greenhouse warming, the frequency of extreme positive IOD (pIOD) events will increase in the future However, there is no information about the different character between extreme and moderate events During the period of 1979-2014, we identified 3 extreme and 4 moderate events Based on composite analysis of surface wind, sea surface temperature (SST) and temperature of the upper ocean, it is indicated there is a distinction on temporal and spatial evolution of equatorial easterly wind anomaly (EEWA) and the mean depth of 20°C isotherm (thermocline) over the eastern part of the equatorial Indian ocean The EEWA was started around June (October) and retreat in November for extreme (moderate) events The thermocline of extreme (moderate) events also showed an earlier shallowing, started in May (October) and reached the most shallow of depth around November Indicating that, during extreme events, the positive Bjerkness feedback strengthened earlier Using mixed layer heat budget analysis, it is revealed that during moderate events, the ocean dynamic process dominantly influences the cooling process of SST only in the peak phase, while during extreme events, the ocean dynamic process has dominant role in the whole process (from initial until peak phase) The early coupled process of EEWA and thermocline in shaping strong SST cooling gives time for us to monitor the developments of extreme pIOD and prepare mitigation against the impact at the peak phase However, the results presented in this study are based on limited samples from observations, thus requiring further clarification with numerical models and analysis of ensemble long integrations.