Characterization of the Vertical Structure of Latent Heating in the East Pacific ITCZ Using the TRMM PR and CLOUDSAT CPR
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In the East Pacific intertropical convergence zone (ITCZ), Tropical Rainfall Measuring Mission (TRMM) radar-based latent heating retrievals suggest a top-heavy structure; however, the TRMM precipitation radar (PR) underestimates light precipitation (< 0.4 mm h?1) from shallow convection and the low-level latent heating associated with this precipitation. Thus, this study uses observations of stratiform and deep convective precipitation from the TRMM PR and shallow precipitation from the more sensitive CloudSat cloud profiling radar (CPR) to assess the seasonal vertical structure of latent heating in the East Pacific ITCZ for 1998-2015. This study is complemented with three reanalysis datasets (MERRA2, ERA-Interim, and NCEP NCAR) to analyze the meridional circulation changes linked to variations in the ITCZ heating profiles. There is a distinct seasonal cycle in the TRMM/CloudSat latent heating profiles in the East Pacific ITCZ. During DJF, latent heating peaks around 850 hPa because of the predominance of rain from shallow convection. The heating peak rises to 700 hPa during MAM as the contribution from deep convective rain increases along with the presence of a mid-level inflow south the ITCZ. During JJA and SON, stratiform precipitation increases significantly and heating is more equally distributed throughout the troposphere with double peaks at 700 and 400 hPa; the lower peak is related to the strong shallow overturning circulation. In addition, the East Pacific has a meridional slope in latent heating throughout the year as a result of the prevalence of shallow convection in the southern part of the ITCZ and deep convection in the northern part of the ITCZ. This slope is weakest during MAM when a double ITCZ structure exists. Reanalyses only capture certain aspects of this seasonal cycle in the East Pacific ITCZ. While the reanalyses agree that the most bottomheavy heating occurs in DJF and the most top-heavy heating occurs in JJA, they greatly underestimate the amount of heating aloft compared to the satellite retrievals throughout the year. This disagreement has serious implications for how the meridional circulation is captured in this region with reanalyses showing varying ability in representing the shallow meridional circulation and deeper Hadley cell overturning in the East Pacific.
Huaman Chuquihuaccha, Lidia (2018). Characterization of the Vertical Structure of Latent Heating in the East Pacific ITCZ Using the TRMM PR and CLOUDSAT CPR. Master's thesis, Texas A & M University. Available electronically from