Analysis and evaluation of WRF microphysical schemes for deep moist convection over south-eastern South America (SESA) using microwave satellite observations and radiative transfer simulations

Abstract

Abstract. In the present study, three meteorological events of extreme deep moist convection, characteristic of southeastern South America, are considered to conduct a systematic evaluation of the microphysical parameterizations available in the Weather Research and Forecasting (WRF) model by undertaking a direct comparison between satellite-based simulated and observed microwave radiances. A research radiative transfer model, the Atmospheric Radiative Transfer Simulator (ARTS), is coupled with the WRF model under three different microphysical parameterizations (WSM6, WDM6 and Thompson schemes). Microwave radiometry has shown a promising ability in the characterization of frozen hydrometeors. At high microwave frequencies, however, frozen hydrometeors significantly scatter radiation, and the relationship between radiation and hydrometeor populations becomes very complex. The main difficulty in microwave remote sensing of frozen hydrometeor characterization is correctly characterizing this scattering signal due to the complex and variable nature of the size, composition and shape of frozen hydrometeors. The present study further aims at improving the understanding of frozen hydrometeor optical properties characteristic of deep moist convection events in south-eastern South America. In the present study, bulk optical properties are computed by integrating the singlescattering properties of the Liu (2008) discrete dipole approximation (DDA) single-scattering database across the particle size distributions parameterized by the different WRF schemes in a consistent manner, introducing the equal mass approach. The equal mass approach consists of describing the optical properties of the WRF snow and graupel hydrometeors with the optical properties of habits in the DDA database whose dimensions might be different (D max ) but whose mass is conserved. The performance of the radiative transfer simulations is evaluated by comparing the simulations with the available coincident microwave observations up to 190 GHz (with observations from Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager (TMI), Microwave Humidity Sounder (MHS) and Special Sensor Microwave Imager/Sounder (SSMI/S)) using the χ 2 test. Good agreement is obtained with all observations provided special care is taken to represent the scattering properties of the snow and graupel species.

Sensitivity study of the planetary boundary layer and microphysical schemes to the initialization of convection over the Arabian Peninsula

“…; Galligani et al . ; Song and Sohn, ). Keep in mind that WDM6 does not interact with aerosol data like the Thompson aerosol‐aware scheme.…”

“…WDM6 is also a double-moment scheme with prognostic equations for the same hydrometeors as the Thompson scheme, but includes a prognostic equation for the cloud droplet concentration, which is prescribed in the non-aerosol aware Thompson scheme. This scheme is also widely used in the WRF community (Bae et al 2016;Galligani et al 2017;Song and Sohn, 2018). Keep in mind that WDM6 does not interact with aerosol data like the Thompson aerosol-aware scheme.…”

Representing Precipitation Ice Species With Both Spherical and Nonspherical Particles for Radiative Transfer Modeling of Microphysics‐Consistent Cloud Microwave Scattering Properties

“…Because of this mass-size relationship inconsistency, a method must be devised for replacing the WSM6 microphysics soft spheres with the nonspherical particles in the Liu database for calculating new cloud scattering properties. This subject has been similarly discussed by Galligani et al (2017), Geer and Baordo (2014), and Eriksson et al (2015). Here we discuss two classes of methods, one based on replacing particles of equal mass, and the other based on replacing particles of equal maximum dimension (which has three variants).…”

“…In Geer and Baordo (), the RTTOV‐SCATT radiative transfer model was modified to use nonspherical ice particles for snow (the only precipitation ice species in the model) instead of soft spheres, and several habits were found to produce a better correspondence between observations and simulations from ECMWF 4D‐Var global analyses; their development of precipitation‐affected radiance assimilation has continued (e.g., Kazumori et al, ). More recently, Galligani et al () applied the scattering properties of nonspherical particles to soft spheres in the particle size distributions of a selection of WRF microphysics schemes to compare simulations of South American thunderstorms.…”

“…Journal of Advances in Modeling Earth Systems 10.1002/2017MS001226 Kazumori et al, 2016). More recently, Galligani et al (2017) applied the scattering properties of nonspherical particles to soft spheres in the particle size distributions of a selection of WRF microphysics schemes to compare simulations of South American thunderstorms.…”