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Climatology and Interannual Variability of Convectively Coupled Equatorial Waves Activity

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  • 1 Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
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Abstract

Climatology and interannual variability of convectively coupled equatorial wave (CCEW) activity, including the mixed Rossby–gravity (MRG), tropical-depression-type (TD-type), equatorial Rossby (ER), and Kelvin waves, are investigated using the satellite-observed brightness temperature data from the Cloud Archive User Service. The monthly activity of CCEWs is represented by the root mean square of the daily filtered convections in each month based on the Wheeler–Kiladis filtering method. More precise seasonal cycles of CCEW activity are obtained from the meridional and zonal mean climatology.

Interannual variance of CCEW activity is further investigated. Kelvin wave activity has maximum interannual variance over the eastern Pacific, while the other three waves are most variable in the intertropical convergence zone. The four active CCEWs all have significant correlation with the background convection and local sea surface temperature (SST) over the central and eastern Pacific, but they are not significantly correlated over other regions. The El Niño events may induce more trapped and active CCEWs over the central and eastern Pacific but weaker MRG and TD-type waves over the warm pool. In contrast, the El Niño Modoki has much weaker correlation with CCEW activity. CCEW activity over the southeastern Indian Ocean is negatively correlated with the Indian Ocean dipole, while that over the western and northern Indian Ocean may be determined by atmospheric internal disturbances. The tropical southern Atlantic mode is the strongest Atlantic SST anomaly mode correlated with the Atlantic CCEW activity.

Corresponding author address: Dr. Ping Huang, P.O. Box 2718, Bei-Er-Tiao 6, Zhong-Guan-Cun, Beijing 100190, China. E-mail: huangping@mail.iap.ac.cn

Abstract

Climatology and interannual variability of convectively coupled equatorial wave (CCEW) activity, including the mixed Rossby–gravity (MRG), tropical-depression-type (TD-type), equatorial Rossby (ER), and Kelvin waves, are investigated using the satellite-observed brightness temperature data from the Cloud Archive User Service. The monthly activity of CCEWs is represented by the root mean square of the daily filtered convections in each month based on the Wheeler–Kiladis filtering method. More precise seasonal cycles of CCEW activity are obtained from the meridional and zonal mean climatology.

Interannual variance of CCEW activity is further investigated. Kelvin wave activity has maximum interannual variance over the eastern Pacific, while the other three waves are most variable in the intertropical convergence zone. The four active CCEWs all have significant correlation with the background convection and local sea surface temperature (SST) over the central and eastern Pacific, but they are not significantly correlated over other regions. The El Niño events may induce more trapped and active CCEWs over the central and eastern Pacific but weaker MRG and TD-type waves over the warm pool. In contrast, the El Niño Modoki has much weaker correlation with CCEW activity. CCEW activity over the southeastern Indian Ocean is negatively correlated with the Indian Ocean dipole, while that over the western and northern Indian Ocean may be determined by atmospheric internal disturbances. The tropical southern Atlantic mode is the strongest Atlantic SST anomaly mode correlated with the Atlantic CCEW activity.

Corresponding author address: Dr. Ping Huang, P.O. Box 2718, Bei-Er-Tiao 6, Zhong-Guan-Cun, Beijing 100190, China. E-mail: huangping@mail.iap.ac.cn
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