The Consistent Behavior of Tropical Rain: Average Reflectivity Vertical Profiles Determined by Rain Top Height

Abstract

AbstractSixteen years of Tropical Rain Measuring Mission (TRMM) reflectivity profile data are collected for oceanic, continental, and island tropical regions within the boreal winter intertropical convergence zone (ITCZ). When sorted by the rain top height (RTH), a consistent behavior emerges where the average reflectivity profiles originating at different RTHs form non-overlapping manifolds in the height–reflectivity space, excluding the brightband regions for stratiform type profiles. Based on reflectivity slope (dBZ km−1) profile characteristics and physical considerations, the profiles are divided into three classes: 1) cold profiles, which originate above the −20°C isotherm height and display convergence to a single reflectivity slope profile independent of RTH; 2) warm profiles, which originate below the 0°C isotherm height and display strong reflectivity slope dependence on RTH, with slope values per RTH linearly decreasing with decreased height; and 3) mixed profiles, which originate at the layer located in between the lowest cold rain and highest warm rain profiles and show a gradual transition from cold profile to warm profile reflectivity slope behavior. Stratiform type profiles show similarity for all regions. It is shown that the typical tropical stratiform cold rain profile can be simply parameterized given the temperature profile. Convective type profiles present larger interregional differences. Their deviation from the typical stratiform cold rain profile is used as a measure for convective intensity, where continental and island regions show larger deviations compared to oceanic ones.