Title: SWIRP: Compact Submm-Wave and LWIR Polarimeters for Cirrus Ice Properties
Presenting Author: Manuel Vega
Organization: NASA GSFC
Co-Author(s): Dong L. Wu, William Deal, Russell Chipman, William Gaines, and Ping Yang

Abstract:
Clouds remain as a major source of uncertainty in climate models. Ice clouds, in particular, are poorly constrained and have been used as a tuning parameter in the models to balance radiation budget at the top of atmosphere and precipitation at the surface. Lack of accurate cloud ice and its microphysical property measurements has led to large uncertainty about global clouds and their processes within the atmosphere. NASA’s Aerosol, Cloud and Ecosystems (ACE), an Earth Science Decadal Survey (DS) mission, recommended an advanced science payload with submm-wave and longwave infrared (LWIR) radiometers for such cloud ice measurement. In a recent community white paper, Cloud and Precipitation Process Measurements (CaPPM), dynamics and microphysical properties are identified as the key links between the cloud-precipitation processes and need more accurate measurements. The SWIRP objective is to enable accurate measurements of cloud ice and its microphysical properties (particle size and shape) with combined conically-scanning submm and IR polarimeters for future remote sensing from space. Radiometric and polarimetric measurements from the SWIRP submm (220 and 680 GHz) and IR (8.6, 11, and 12 μm) bands provide the needed sensitivity over a full dynamic range of cloud ice. The conical scanning configuration in SWIRP will preserve horizontal (H) and vertical (V) polarization information for bulk cloud particle shape retrievals while the matched submm and LWIR footprints allow determination of cloud particle size from the scattering radiances at these frequencies. The compactness of SWIRP design enables cost-effective, flexible deployment of such radiometers-polarimeters in future spaceflight missions (e.g., ACE) for rapid update and frequent revisit sampling to study fast atmospheric processes.