Analysis and validation of cloud and precipitation microphysical properties of deep moist convection over  South Eastern South America (SESA), using observation and modeling tools 

V. GALLIGANI; D. WANG; C. PRIGENT; P. SALIO

Bologna

Conferencia; 8th IPWG & 5th IWSSM Joint Workshop; 2016

The continental region east of the Andes and covering the north and centre of Argentina, south of Brazil,Paraguay and Uruguay, usually referred to as southeastern South America (SESA), is known for its large                      and intense mesoscale convective systems (MCs) within which severe events develop. SESA MCSs stand                            out as among the strongest on earth in satellite observations. In this data sparse region, little is known of the                                        aspects of these systems including what governs their structure, life cycle, similarities and differences with                              severe weather­producing systems observed elsewhere, and their predictability on weather to climate                      timescales. The present study aims to advance into the knowledge of such physical processes involved in                                the developing phase of MCSs where the convective region is particularly active and on the triggering                              mechanisms associated to their initiation. The focus of present study is especially on the analysis of cloud                                  microphysical parameterizations of the Weather Research and Forecasting (WRF) model. Cloud resolving                      models like WRF can be operated with different cloud microphysics schemes. Those microphysics schemes                            include different microphysics species and processes between those species. Extensive validations for                        existing schemes are needed in order to constrain and reduce uncertainties. The microphysical properties                            (e.g., dielectric properties, density, particle size distribution, shape, orientation) of the frozen particles                          specifically, have a very complex temporal and spatial variability, and lack robust parameterizations. There                            is a pressing need to constrain such microphysical properties in order to reduce the large uncertainties                              associated with frozen quantities in Numerical Weather Prediction (NWP) and cloud resolving models.                          Microwave radiometry has shown a promising ability in the characterization of iced particles, as it is able to                                    penetrate and provide insight into the vertical profiles of most clouds, in contrast to infrared and visible                                  observations, which essentially sense cloud tops. One way to verify the good behavior of a microphysical                              scheme, and consequently the representativity of the cloud simulations, is to perform radiative transfer                            simulations with inputs, (1) the atmospheric profiles provided by the cloud model (i.e. in this work WRF                                  simulations of deep moist convection events in particular situations of central/northern Argentina and                          southern Brazil using the WSM6, WDM6 and the Thompson schemes) and (2) a rather accurate description                                of the radiative properties of each microphysical species. The radiative transfer simulations are to be                              carefully compared to the coincident satellite observations, at the same frequencies, geometry, and mode                            (active and passive). This exercise requires not only the cloud simulations to be as close as possible to the                                      reality, i.e. good location in time and space of the studied clouds relative to the observations, but also                                    realistic radiative properties of the clouds to reproduce the magnitude of the satellite observations.