Observed Changes in the Morphology of TRMM Precipitation Features in the ITCZ

Recent studies indicate that the Hadley circulation has been strengthening and expanding over the past few decades. Because the Intertropical Convergence Zone (ITCZ) constitutes the ascending branch of this thermally direct circulation, it is important to understand the corresponding ITCZ changes. Our recent work using a 36-year climatology of Pacific ITCZ characteristics derived from ERA-Interim, the Global Precipitation Climatology Project (GPCP), and the Tropical Rainfall Measuring Mission (TRMM) shows a narrowing of the ITCZ's meridional extent, with a simultaneous increase in precipitation intensity. Similar studies using climate models suggest that this trend will continue in the future. While these trends in the ITCZ extent and precipitation are influenced by the warming climate, the exact mechanism for the ITCZ changes and how the narrowing and intensification relates to the characteristics of convective systems within the ITCZ is still unclear. In an effort to better understand the relationship between ITCZ variability and the convection within the ITCZ, TRMM precipitation features within the ITCZ are identified and the distribution of convective characteristics are examined. The frequency distributions of convection intensity metrics such as maximum height of the 30 dBZ echo, volumetric rain rate, and the size of precipitation features will be used to characterize convection in the ITCZ. Preliminary results suggest that the density of convective features near the ITCZ center decreases when the ITCZ is wide and increases when the ITCZ is narrow.