Microwave-IR Polarimetric Radiometry for Ice Clouds: SWIRP Update
Presenting Author: Dong Wu
Organization: Goddard Space Flight Center
Co-Author(s): Giovanni De Amici, Manuel Vega, William Deal, Russell Chipman, William Gaines, and Ping Yang
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 models to balance the radiation budget at the top of atmosphere and precipitation at the surface. Lacks of accurate measurements of cloud ice and its microphysical properties lead to large uncertainty about global clouds and their processes within the atmosphere. The new instrument, called Submm-Wave and LWIR Polarimeter (SWIRP), is to measure polarimetric radiation of cloud scattering at mm-submm (220 and 680 GHz) and IR (8.6, 11, and 12 micron) bands, and derive microphysical properties (particle size and shape) over a wide dynamic range of cloud ice. It seeks to fill the sensitivity gap in cloud ice measurements from microwave and IR sensors, to provide deeper understanding of cloud-precicipitation-radiation processes as highlighted in the 2017 Decadal Survey. The instrument in development is a compact (20x20x40 cm), conical scanner with matched footprint sizes and onboard accurate radiometric and polarimetric calibration. The conical-scan configuration with SWIRP allows horizontal (H) and vertical (V) polarization information in each scan from space such that cloud ice and microphysical properties can be simultaneously retrieved. The SWIRP miniaturization is enabled by new technologies in low-power, direct-detection receivers at mm/submm wavelengths, a multi-channel longwave IR (LWIR) spectro-polarimeter, and a compact Bearing and Power Transfer Assembly (BAPTA). The project goal is to advance the instrument system TRL from 3 to 5 in three years.