A Further Look at Q1 and Q2 from TOGA COARE

Abstract

wo features of Yanai et al.?s profiles of Q1 and Q2?the commonly observed double-peak structure to Q2 and an inflection in the Q1 profile below the melting level?are explored using estimates of convective and stratiform rainfall partitioning based on Massachusetts Institute of Technology (MIT) radar reflectivity data collected during TOGA COARE. The MIT radar data allow the Q1 and Q2 profiles to be classified according to stratiform rain fraction within the radar domain and, within the limitations of the datasets, allow interpretations to be made about the relative contributions of convective and stratiform precipitation to the mean profiles. The sorting of Q2 by stratiform rain fraction leads to the confirmation of previous findings that the double-peak structure in the mean profile is a result of a combination of separate contributions of convective and stratiform precipitation. The convective contribution, which has a drying peak in the lower troposphere, combines with a stratiform drying peak aloft and low-level moistening peak to yield a double-peak structure. With respect to the inflection in the Q1 profile below the 0°C level, this feature appears to be a manifestation of melting. It is the significant horizontal dimension of the stratiform components of tropical convective systems that yields a small but measurable imprint on the large-scale temperature and moisture stratification upon which the computations of Q1 and Q2 are based. The authors conclude, then, that the rather subtle features in the Q1/Q2 profiles of Yanai et al. are directly linked to the prominence of stratiform precipitation within tropical precipitation systems.