The Joint Center for Satellite Data Assimilation develops the Community Radiative Transfer Model (CRTM) in partnership with NOAA NESDIS/STAR, the Environmental Modeling Center, NASA, the U.S. Navy and the Air Force. The CRTM serves as the observation operator within the JEDI/UFO framework used for NOAA’s global and regional data assimilation, and it is also the tool that converts UFS forecast fields into simulated satellite radiances for evaluation in observation space.
This webinar introduces the CRTM to the broader UFS community, with emphasis on the interface between UFS model physics and the forward operator. Hydrometeor species and effective radius conventions, land and snow surface states from Noah-MP, and aerosol speciation from GOCART must each be translated into optical properties before a radiance can be simulated. We will show how sensitivity to these translation choices appears in observation space, and why closer alignment between UFS physics and CRTM assumptions matters for both assimilation and verification.
We will summarize the current state of CRTM v3, including the transition to netCDF coefficients and a rebuilt coefficient generation capability that reduces support for new sensors from weeks to hours. We will also describe how UFS developers can run the CRTM against their own model output, and invite community input on which UFS surface, cloud and aerosol variables the CRTM should be using.
Dr. Benjamin T. Johnson, UCAR/JCSDA @ NESDIS/STAR
Dr. Benjamin T. Johnson is a Scientist VI at the University Corporation for Atmospheric Research, working with the Joint Center for Satellite Data Assimilation, where he leads development of the Community Radiative Transfer Model (CRTM). He holds a B.S. in Physics from Oklahoma State University, an M.S. in Atmospheric Science from Purdue University, and a Ph.D. in Atmospheric Science from the University of Wisconsin-Madison. His graduate research on variable-density ice particle models and dual-frequency radar retrieval of precipitation size and phase established the direction of his later work on spaceborne precipitation algorithms.
From 2007 to 2015 he was based at NASA Goddard Space Flight Center through the University of Maryland Baltimore County as a member of the GPM science team, developing physically based precipitation retrieval algorithms from combined passive microwave and dual-frequency radar observations. He developed the Single Particle Melting Model for computing microwave scattering by realistically shaped melting aggregates, which was incorporated into the operational GPM combined radar-radiometer algorithm, and contributed to the nonspherical snow particle scattering databases underpinning the GPM retrieval framework. He served as mission scientist for the IPHEx, GCPEx and MC3E field campaigns, as instrument scientist for CoSMIR, and received the NASA Goddard R.H. Goddard Award for Exceptional Achievement in Science in 2015. He subsequently joined Atmospheric and Environmental Research at NOAA STAR, where he developed the Community Active Sensor Module, the CRTM forward operator for spaceborne radar and lidar.
Since 2017 he has led the CRTM, directing release management, coefficient generation for new and emerging sensors, and long-term development strategy, in collaboration with NOAA NESDIS/STAR and OMD, NASA, the U.S. Navy, the U.S. Air Force, ECMWF, EUMETSAT and the UK Met Office. He is a science team member for the NASA PolSIR submillimeter ice cloud mission and the HyMPI hyperspectral microwave instrument. He co-chairs the ITWG Radiative Transfer and Surface Properties Working Group, and currently serves as a Handling Editor for the Journal of Atmospheric and Oceanic Technology
