EQUATORIAL ROSSBY WAVE ACTIVITY AND ITS IMPACT ON MOISTURE TRANSPORT AND MADDEN-JULIAN OSCILLATION (MJO) PROPAGATION OVER THE MARITIME CONTINENT

• Main Author: Andika
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/68915
• Institution: Institut Teknologi Bandung

This study examines equatorial Rossby (ER) wave activities over the Maritime Continent in association with the propagation of Madden-Julian Oscillation (MJO) during crossing (MJO-C) and blocked (MJO-B) events. Previous studies have pointed out that the MJO-B event is characterized by a westward dry anomaly propagation called transient dry precursor (TDP) but the roles of ER waves in such events have not been thoroughly studied. Herein, 21 MJO-C and 12 MJO-B events from 1998 to 2015 identified in a previous study, are analyzed. Composite analysis of Vertical Integrated Moisture Transport (VIMT) was first performed to study the differences in moisture transport anomalies. Space-time spectral analysis was then applied to Outgoing Longwave Radiation (OLR) data to identify ER wave activities. The resulted wavenumber-frequency spectra were used in further analyses. The results show that MJO-B events were characterized by a weakening of low (below 700hPa)-level moisture transports towards the Indian Ocean related to an initial TDP event in the Pacific Ocean, which is strongly associated with westward propagating ER waves. Although ER wave activities were identified in both MJOC and MJO-B events, those waves in MJO-B events have a certain amplitude and phase to induce strong winds in the Indian Ocean that can cause reduction of moisture transports needed to enhance convections for the earlier stage of MJO development.