A STUDY OF ENSO-QBO INTERACTION AS REVEALED BY GRAVITY WAVE ACTIVITIES IN THE UPPER TROPOSPHERE AND LOWER STRATOSPHERE

• Main Author: Rasyad, Firas
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69154
• Institution: Institut Teknologi Bandung

This study focuses on gravity wave (GW) activities in the upper troposphere and lower stratosphere (ULTS) over the equatorial region during the El Niño Southern Oscillation (ENSO) and Quasi-Biennial Oscillation (QBO) phases analyzed as gravity wave potential energy (Ep GW) variations. The Ep GW was calculated from temperature profiles of the Global Navigation Satellite System Radio Occultation (GNSS RO) observation from COSMIC satellite that reconstructed with full spectrum inversion (FSI) method. Herein, the UTLS region is defined by altitudes of 20-27 km, whereas the GWs of concern have vertical wavelengths (????????) of two types: (1) 0.5<????????<3 km and (2) ????????<1 km. Composite analysis is applied to characterize Ep GW under different ENSO and QBO phases. Furthermore, the longitudinal variations of Ep GW are also analyzed. The results show that, in general, Ep GW of 0.5<????????<3 km vertical wavelength reach a maximum value in the lower UTLS and decreasing with altitude. During the El Niño phase, the Ep of these waves increases in the lower UTLS, while the opposite occurs during La Niña. Furthermore, it is found that if the active phase of ENSO occurs during the westerly phase of QBO, a similar pattern for Ep appears in association with a changing zonal wind with altitude. Conversely, a strengthening of zonal winds during easterly QBO does not seem to be related to the GW acitivities in UTLS. Additionally, it is found that smaller sale GW of ????????<1 km appears to be more active during the transition of westerly to easterly QBO.