Variability features of the width of the tropical belt from COSMIC radio occultation data

In this work, we analyzed time-series and trends of the tropical belt edges and widths with three methods based on the tropopause using new global positioning system radio occultation (GPS RO) data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission for September 2006–February 2014. The results from the three methods agreed well with previous studies and new features were found. To avoid the El Nino Southern Oscillation (ENSO) and Quasi-Biennial Oscillation (QBO) influence, we applied a simple multiple linear regression model to the monthly anomalies to obtain the tropical belt edges and width trends. During the study, we found equatorward movements of the tropical belt edges on both hemispheres. The narrowing of the tropical belt mainly occurred in the Pacific Ocean. We also found that the deseasonalized monthly anomalies of the tropical belt width were closely related with the ENSO and QBO. The tropical belt at a height of 15 km was mostly closely related with the ENSO. The correlations between the QBO and the tropical belt were consistent for the three methods.