Evolution of the vertical structure of warm rain with detailed microphysics: Comparison against laboratory and field data from a vertically pointing radar

In this work, a one-dimensional rainshaft model with detailed microphysics is presented to describe the evolution of the raindrop spectra in warm rain. The microphysical processes include the treatment of coalescence, collisional breakup, condensation, and evaporation. The evolution of the droplet size distribution (DSD) under the influence of combined mechanisms is observed as the drops fall through the atmospheric column. The goal of the present study is double. The first aim is to develop a model that predicts the evolution of the rainfall microstructure in warm rain and that uses updated description of collisional breakup dynamics. The second aim is to use real rainfall data in order to validate and parameterize the microphysical processes involved in the evolution of the DSD. The ultimate goal of this study is to achieve a significant step towards a dynamic simulation of DSD that will be used for physical algorithms in radar rainfall estimation. In addition future developments of the model will focus on the role of the presence of aerosols and their impact on the development of clouds and on rain initiation mechanisms. Numerical results obtained with the column model are compared against experimental data. The comparison of modeling results with experimental data is performed in two ways. First, the model is used to replicate tower-based laboratory experiments with a focus on breakup dynamics. The second aspect of model validation concerns the comparison with rainfall data collected during field campaigns using a vertically pointing radar. Simulated and experimental vertical profiles are compared for the drop number concentration, the liquid water content (LWC), the radar reflectivity factor (Z), and the mean raindrop diameter.