Observations of temperature, wind, cirrus, and trace gases in the tropical tropopause transition layer during the MJO

Abstract

Satellite observations of temperature, optically thin cirrus clouds, and trace gases derived from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and the Microwave Limb Sounder (MLS) are analyzed in combination with Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) wind and humidity fields in the tropical tropopause transition layer (TTL), using the Madden-Julian oscillation (MJO) as a carrier signal. MJO-related deep convection induces planetary-scale Kelvin and Rossby waves in the stably stratified TTL. Regions of ascent in these waves are associated with anomalously low temperatures, high radiative heating rates, enhanced cirrus occurrence, and high carbon monoxide and low ozone concentrations. Low water vapor mixing ratio anomalies lag the low temperature anomalies by about 1-2 weeks. The anomalies in all fields propagate eastward, circumnavigating the tropical belt over a roughly 40-day interval. Equatorial cross sections reveal that the anomalies tilt eastward with height in the TTL and propagate downward from the lower stratosphere into the upper troposphere. As MJO-related convection moves into the western Pacific and dissipates, a fast-moving Kelvin wave flanked by Rossby waves propagates eastward across South America and Africa into the western Indian Ocean. The region of equatorial westerly wind anomalies behind the Kelvin wave front lengthens until it encompasses most of the tropics at the 150-hPa level, giving rise to equatorially symmetric, anomalously low zonal-mean temperature and water vapor mixing ratio and enhanced cirrus above about 100 hPa. © 2014 American Meteorological Society.