Variation of the Wind Profiles in the Tropical Tropopause Layer Associated with QBO-MJO Connection: An Equatorial Atmosphere Radar Observation

Abstract

AbstractThe Quasi-Biennial Oscillation (QBO) is known as the alternating zonal wind in the stratosphere that is discovered to have a connection with tropospheric Madden–Julian Oscillation (MJO), particularly during the northern hemisphere winter. Discussion on the variation of wind profiles in the tropical tropopause layer (TTL), the transition layer between troposphere-stratosphere at 14–18.5 km, related to QBO-MJO connection is still limited due to the availability of high vertical and temporal resolution of observation data. We investigate 3-D wind profiles by Equatorial Atmosphere Radar (EAR) with 150 m vertical resolution during extended boreal winter (November to March) throughout 2003–2009 (16 years). We find five MJO active cases in the easterly QBO phase (QBOE), six during the westerly QBO phase (QBOW), and 20 in the transition phase or neutral QBO (QBON). The QBO index is defined as the change of zonal wind at 18.7 km obtained from EAR data. We observed radar tropopause (maximum echo power within TTL) to be lifted to 17.4 km during MJO active associated with QBOE compared to MJO active period during QBOW (16.7 km) and QBON (16.8 km). We also discover that vertical wind is stronger above the tropopause, representing more updraft activity (0.02–0.03 m/s) in QBOE than QBOW and QBON.KeywordsEARWind profileQBO-MJO connectionTTL