Modeling and observations of drizzle production in stratiform clouds

Description

The production of drizzle size particles via autoconversion is a key microphysical process that needs to be accurately parameterized in numerical models of various scales and resolutions. A 1-D steady-state microphysical approach to modeling the early production and vertical evolution of the drizzle particle size distribution in warm stratiform clouds is used to analyze observational data. The formation rate of embryonic drizzle droplets due to the autoconversion process is calculated using a number of proposed formulations. In addition, accretion and evaporation processes are explicitly modeled. The microphysical model is used as input to a radar Doppler spectrum forward model, and synthetic radar Doppler spectra moments are generated. The forward modeled radar Doppler spectra are used to: i) test the sensitivity of radar Doppler spectra observations to detect early drizzle production and ii) evaluate the various parameterizations of early drizzle growth near the cloud top and growth by accretion of well-developed drizzle.