4. Precipitating clouds consist of a wide range of particles with variable shape, size, number density, and composition, and microwave radiation is sensitive to these properties
5. Furthermore, ice clouds, water clouds, and gases and attenuate/emit microwave radiationB. Johnson IGARSS 2011 3/22
9. An inversion method for retrieving the desired physical properties given observationsB. Johnson IGARSS 2011 4/22
10.
11.
12. Pros: Simple to implement, works equally over land and water
13. Cons: “matches” may not represent reality, geometric issues ignored (NUBF, beam matching)
14. Important note: the uncertainty due to unknown particle shape is orders of magnitude greater than other known sources of uncertainties.B. Johnson IGARSS 2011 5/22
15. Retrieval Schematic (1) Radar-only Retrieval Large set of Radar-Retrieved Vertical Profiles of PSD/IWC Observed Reflectivities (Zku, Zka) Inversion Z-S, DWR, etc. Attenuation “Correction” (2) Forward Model Physical - Radiative Database Physical Model Precip. & Atmos. Hydrometeor Model Ext., Scat., p(Q), Z Radiative Transfer Model (3) Radar/Radiometer Retrieval Simulated Radiances (TBsim) TB Constrained PSD/IWC Profiles PMW Retrieval Algorithm Observed Radiances (TBobs) 6/22
16. Observed Reflectivities and Passive Microwave TBs during the 2003 Wakasa Bay Experiment B. Johnson IGARSS 2011 7/22
17. (Const. Density Spheres) Retrieval Inputs at each vertical level Environment: Pressure, Temperature, Humidity, Cloud Water Content Microphysics: Particle Density, Shape, PSD Type Observables: Zm,14, Zm,35, DWR Forward Dual Wavelength Ratio Retrieval Method Update PIA for air, clouds, and precip. (A14, A35) Starting at storm top (ztop) down to z=0 PIA-corrected Reflectivities Ze,14, Ze,35 B. Johnson IGARSS 2011 8/22 Match DWR with D0 (3.67/L) in Database; compute N0 Is DWR 1? no yes Ze,35-IWC retrieval, infer D0 / N0
18. WBAY 03: Dual Wavelength Ratio, and retrieved N0, and D0 (assuming a single constant particle density) B. Johnson IGARSS 2011 9/22
33. The choice of particle shape and size distribution appears to be the largest uncertainty in physically-based precipitation retrieval algorithms (most certainly renders them ill-posed)
34. So, prior knowledge of the particle shapes and sizes should significantly constrain physically based retrievals
35. However, this requires that one has already computed the necessary physical-radiative properties ahead of time!B. Johnson IGARSS 2011 20/22
36.
37. Create complete database of IWC as a function of reflectivity, dual-wavelength ratio, and particle shape.