OBSERVATIONS OF MIXED ROSSBY-GRAVITY (MRG) WAVES AS A MJO CONVECTIVE CLOUD INITIATION USING GNSS-RO DATA
Herdiana Sri Wahyuningsih1, Nurjanna Joko Trilaksono2, Noersomadi3

1 Earth Science Program, Institut Teknologi Bandung, Indonesia
2 Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Indonesia
3 Research Center for Climate and Atmosphere, National Research and Innovation Agency (BRIN), Bandung, Indonesia

Abstract

The Madden Julian Oscillation (MJO) is the intra seasonally eastward propagation of convective activity initiated from the Indian Ocean then passing through the Maritime Continents and continued to the Pacific Ocean. The aim of this study is to determine the role of a weekly westward Mixed Rossby Gravity (MRG) waves in triggering MJO convective clouds by analyzing the vertical temperature fluctuations in the upper troposphere and lower stratosphere. We investigate temperature profile, which has a vertical resolution of 0.1 km, retrieved with the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC2) Global Navigation Satellite System Radio Occultation (GNSSRO). We applied space-time spectral analysis at 14 km (upper troposphere), 17 km (tropopause) and 21 km (lower stratosphere) to elucidate the wave interaction within the pre-, during and post-MJO phase. In the pre-MJO phase, the MRG initiates the thermal variations between the upper troposphere (warm anomaly) and tropopause (cold anomaly) form a likely dipole stratification due to the relaxation of latent heat released from the convective clouds. The height and longitude time cross section shows an eastward tilt with height wave propagation from the Indian Ocean to the Western Pacific.

Keywords: MJO, MRG, COSMIC2-GNSSRO, Mid-troposphere

Topic: EARTH, ATMOSPHERIC, AND SPACE SCIENCE