7B.4 Relating the Morphology of Convection to ITCZ Extent

Tuesday, 9 January 2018: 2:15 PM
616 AB (Hilton) (Austin, Texas)
Kyle Robert Wodzicki, Texas A&M, College Station, TX; and A. D. Rapp

Over the past three decades, the Intertropical Convergence Zone (ITCZ) has narrowed and precipitation rates within the ITCZ have increased, consistent with prevailing theories of convective zone shifts with warming. However, how the morphology of convective systems within the ITCZ evolves with narrowing and intensification has not yet been examined. A better characterization of these changes will help to not only improve our knowledge of ITCZ variability, but may also help to better understand the coupling between convective processes and the large-scale circulation. Using ITCZ boundary identifications derived from ERA-Interim and Tropical Rainfall Measuring Mission (TRMM) data, along with the TRMM Precipitation Feature (PF) database, convective systems within the ITCZ are identified and their morphology is analyzed for the 17 years of TRMM data from 1998-2014. Distributions of convective intensity metrics such as volumetric rain rate, maximum height of the storm, and convective and stratiform rain fractions are partitioned based on the width of the ITCZ to determine how storm morphology changes as the ITCZ narrows. Preliminary analysis indicates that when the ITCZ is narrow the frequency of storms with large volumetric rain rates, high maximum heights, and convective rain fractions greater than 50% (i.e., large, deep PFs that are predominantly convective) increases (decreases) near the center (edges) of the ITCZ. When the ITCZ is wide, the changes have the opposite sign. While these findings point to a strengthening (weakening) of convection when the ITCZ is narrow (wide), the signal has a highly seasonal component and appears to be heavily influenced by ENSO.

- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner