The response to the tropical intraseasonal oscillation in the tropopause region

Using outgoing longwave radiation (OLR) and upper tropospheric water vapor from the Microwave Limb Sounder, we investigate the relationship between the tropical intraseasonal oscillation (TIO) and variations in the tropopause region on intraseasonal timescales. We use multivariate EOF analysis with a time component to establish statistical links among fields. Confirming previous studies, these links indicate that convection associated with the TIO (as revealed by OLR) exists over a limited longitudinal domain and acts to moisten the upper troposphere locally. The responses of temperature and water vapor at the tropopause are more complex: at these levels, the TIO is not limited in longitude. Over the longitudes where the TIO modulates convection, tropopause-level disturbances tend to be locally out of phase with the upper troposphere, with cooling and drying occurring above convection. This response is more sharply confined to the equator than the upper tropospheric signature of the TIO.