Anvil-radiation diurnal interaction: shortwave radiative-heating destabilization driving the diurnal variation of convective anvil outflow and its modulation on the radiative cancellation

Abstract

The behavior of convection producing anvil clouds is neither well derived from current available observations nor well represented in models. In this work, a novel convective cloud data product is designed to capture the convective anvil outflow. Convective organizations and life stages are derived from the images of infrared brightness temperature (BT) of geostationary (GEO) satellites based on a variable-BT segment-tracking algorithm, which allows the possibility for quantifying the convective anvil outflow. Vertical structures of convection are measured by sensors of the A-Train constellation, which provides the cross section of convective outflow. Here, GEO-based convective tracking and A-Train-detected cloud vertical profiles are combined to develop a novel comprehensive GEO-A-Train Merged (GATM) convective cloud data product for investigating the process of convective anvil outflow. On the basis of this novel Lagrangian-view GATM data, the anvil production for mesoscale convective systems (MCSs) can be quantified. The results show that daytime MCSs can produce more anvil clouds than nighttime MCSs. During the daytime, shortwave radiative heating strongly destabilizes the MCS top to promote the anvil outflow with strong divergence, whereas the nighttime divergence driven by the longwave radiative cooling through radiative destabilization and circulation is weak. Moreover, the assessed sensitivity of the radiative budget to the diurnal-cycle phase shift of the convective anvil outflow is approximately 1Wm2 h1 when the phase shift is in the range between 4 and 8 h (otherwise the sensitivity has the same magnitude but positive). Stronger diurnal-cycle amplitude can further amplify this sensitivity. Overall, this work presents the observed anvil-radiation diurnal interaction process: radiative heating determines the diurnal variation of anvil outflow; in turn, the diurnal variation of anvil outflow determines the Earth's radiative budget.