Observed Three Dimensional structure of the Madden-Julian Oscillation and Convectively Coupled Kelvin Waves

The Madden-Julian Oscillation (MJO) and Kelvin waves coupled to convection are separately isolated through space-time spectral and EOF analysis of long record of Outgoing Longwave Radiation (OLR) in the tropics. The three dimensional dynamical structure of these disturbances is described using wind, temperature, pressure, and humidity data from radiosondes and ECMWF reanalysis. Maximum perturbations in wind and temperature are observed at the level of the tropopause and in the lower stratosphere. The eastward tilt with height of these features is consistent with a forced Kelvin wave response to the eastward propagating heat source characterized by the waves. Opposite tilts of the dynamical fields are observed in the mid-to-lower-troposphere, with positive temperature perturbations occurring within the layer of maximum diabatic heating associated with the convection. Important differences in the near-surface temperature and moisture fields between the MJO and the Kelvin waves are also discussed.