Bulk hydrometeor optical properties for microwave and sub-millimetre radiative transfer in RTTOV-SCATT v13.0

Abstract. Satellite observations of radiation in the microwave and sub-millimetre spectral regions (broadly from 1 to 1000 GHz) can have strong sensitivity cloud precipitation particles atmosphere. These (known as hydrometeors) scatter, absorb, emit according their mass, composition, shape, internal structure, orientation. Hence, applications including weather forecasting, geophysical retrievals model validation. To simulate these requires a scattering-capable radiative transfer an estimate bulk optical properties hydrometeors. This article describes module used integrate single-particle over particle size distribution (PSD) provide for Radiative Transfer TOVS scattering code, RTTOV-SCATT, widely fast model. Bulk be derived range models Mie spheres (liquid frozen) non-spherical ice habits Liu Atmospheric Simulator (ARTS) databases, which include pristine crystals, aggregates, hail. The effects different PSD options on simulated brightness temperatures are explored, based analytical two-stream solution homogeneous slab. hydrometeor “spectrum” below GHz is described, along with its sensitivities composition or ice), shape. behaviour frozen changes frequencies above 200 GHz, moving towards optically thick emission-dominated regime more familiar infrared. region little explored but will soon covered by Ice Cloud Imager (ICI).