The Seasonal and Annual Changes of the Tropical Belt

Finding tropical width metrics which are globally observable, but that relate to concepts such as the Hadley circulation, is a challenge. This study uses tropopause heights and tropospheric stability, calculated from COSMIC RO satellite data, to evaluate the seasonal cycle of regional tropical width in reanalyses (ERA-Int, MERRA2, JRA55, and CFSR) at a regional level. We use four previously defined metrics for our comparison. In addition to evaluating the width estimates from reanalyses, we demonstrate the need to carefully document not just the metrics themselves, but the procedures by which the data are handled. For example, we find that dataset resolution can play as large a role in regional tropopause determination as the choice of metrics. While tropical zonal mean width estimates from tropopause height and static stability are only modestly correlated with the Hadley cell and other metrics in time, their regional structure agrees with other metrics in recent literature.