Recent Developments in the Assimilation of Microwave and Radar Observations Into NWP Models

Dr. Isaac Moradi

University of Maryland & NASA Global Modelling and Assimilation Office

Monday February 27, 2023, 2 PM ET


Hybrid (In-Person & Virtual):

This seminar will be held at room 4102 of ESSIC, 5825 University Research Ct. College Park, MD 20740. In-person attendance is welcome with refreshment provided. Zoom is also provided for virtual participants.



Microwave observations play a very important role in improving the weather forecasts. Although these observations are routinely assimilated into NWP models in clear-sky conditions, assimilation of all-sky microwave observations is very limited. Two main factors contributing to this limitation are inaccuracy in the input cloud and hydrometeor profiles used as input to the radiative transfer model and also error in scattering calculations performed by the radiative transfer model itself. The Mie theory is used by many fast RT models to estimate the optical properties of single particles. The Mie theory assumes spherical shapes for ice or snow particles with mixture of air and ice. However, hydrometeors scattering radiation at microwave frequencies have different shapes, sizes, and orientations. Therefore, using Mie theory to determine their optical properties leads to large uncertainties in all-sky radiative transfer calculations.

The discrete dipole approximation (DDA) which approximates the optical properties of large objects in terms of discrete dipoles has shown promise in calculating the scattering properties of particles with different shapes in the microwave frequencies. This presentation focuses on recent advancements in the CRTM scattering calculations for frozen hydrometeors in the microwave frequencies using the DDA technique. In addition to using stand-alone CRTM calculations using collocated ATMS and reanalysis profiles, the data assimilation experiments conducted using the NOAA FV3GFS forecast system are used to evaluate the scattering improvements.

Additionally, the backscattering information from the DDA database was used to implement a radar simulator into CRTM. The radar operator takes advantage of CRTM different modules to calculate clouds absorption and scattering properties. In addition to the forward model both adjoint and tangent linear of the radar simulator are implemented and evaluated as well. The radar simulator is currently being tested within the JEDI/GEOS data assimilation framework to facilitate the assimilation of radar measurements such as CloudSat CPR and GPM DPR into the NASA GEOS model.



Dr. Isaac Moradi is a research scientist at University of Maryland affiliated with NASA Global Modelling and Assimilation Office with over fifteen years of experience specializing in radiative transfer modeling; Observing System Simulation Experiments (OSSE); data assimilation; satellite data analysis and bias correction; and developing microwave instruments. He is currently the PI of multiple projects targeting enhancing the assimilation of microwave and radar measurements into the NWP models especially by improving the forward radiative transfer models for such observations. He is also the Co-I of two projects (funded by NOAA and NASA) to develop the next generation of hyper-spetcral microwave instruments.

Dr.Moradi has a Ph.D. in Climatology and Environmental Planning from University of Tehran and a second Ph.D. in Radio and Space Science from Chalmers University of Technology (Sweden). Prior to joining University of Maryland, he worked at Lulea University of Technology (100 miles above the Arctic Circle) and also University of Tehran.


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Feb 27 2023


John Xun Yang