The interaction between local factors and the Convectively Coupled Equatorial Waves over Indonesia during the Western North Pacific and Australian monsoon phase

A tropical larger scale perturbation by the Convectively Coupled Equatorial Waves (CCEW) is often observed as a precursor to influence weather condition over the Indonesian archipelago, which is also known as the Maritime Continent (MC) area. This study examines the interaction between local factor with regard to convection and vertical interferences on the local scale constrain toward CCEW over Indonesia during an extreme Western North Pacific (WNP) and Australian (AU) monsoon phase. This study is utilizing a 15 year-long (2001-2015) Tropical Rainfall Measuring Mission (TRMM) 3B42 dataset to filter CCEW, i.e. Kelvin, Equatorial Rossby (ER) and Mixing Rossby-Gravity (MRG) waves using the space-time spectra analysis. Furthermore, an Empirical Orthogonal Function (EOF) 1 and 2 then employed on the region of Indonesia to performs each wave evolution, which then analyzed together with a daily precipitation anomaly and multilevel wind among seven locations in Indonesia to seek its local-CCEW interaction. This study finds that there is evidence of local convection associated with Kelvin waves in the afternoon through evening in Tangerang, Surabaya, and Makassar duringWNP monsoon phase. Meanwhile, the local convection associated with MRG during a similar period is persisted only in Makassar at the last evolution day, while there is no clear interaction toward local factor for ER. The apparent of low-level westerly winds coupled with convection for Kelvin waves is significant in Tangerang, Surabaya, and Makassar during the WNP monsoon phase, while the interaction is less significant for MRG-coupled convections (except in Makassar during a similar monsoon phase) and absence for ER. This study suggests that the Kelvin wave revealed as a global scale phenomenon that can be associated with local scale factors in controlling convection, particularly during an extreme WNP phase in Indonesia.