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Brian Wilson, Attila Komjathy, Vardan Akopian, Xioaqing Pi, Chi Ao, and Byron Iijima

Brian Wilson, Attila Komjathy, Vardan Akopian, Xioaqing Pi, Chi Ao, and Byron Iijima. JPL/USC GAIM: Assimilating COSMIC occultations & Sample Applications. Jet Propulsion Laboratory California Institute of Technology M/S 138-308 4800 Oak Grove Drive Pasadena CA 91109

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Brian Wilson, Attila Komjathy, Vardan Akopian, Xioaqing Pi, Chi Ao, and Byron Iijima

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  1. Brian Wilson, Attila Komjathy, Vardan Akopian,Xioaqing Pi, Chi Ao, and Byron Iijima • JPL/USC GAIM: • Assimilating COSMIC occultations & • Sample Applications Jet Propulsion Laboratory California Institute of Technology M/S 138-308 4800 Oak Grove Drive Pasadena CA 91109 Email: Brian.Wilson@jpl.nasa.gov Space Weather Workshop 2008, Boulder, CO

  2. Outline • Global Assimilative Ionosphere Model (JPL/USC GAIM) • First-principles physics model, with an adjoint • Assimilation by Kalman filter and 4DVAR • Assimilating COSMIC TEC improves profile shapes • Three case studies: Arecibo, Jicamarca and Millstone ISR • Extensive validation using Jason VTEC, ISR profiles, ionosonde • Storm Studies • TEC and density profile perturbations during August 7, 2006 storm • Ray Tracing Capability Added to GAIM • Trace ray bending thru 3D electron density field • Application: Improving neutral atmosphere retrievals from COSMIC • Short-Term Forecast (2-6 hours) • Adjust drivers using 4DVAR; feed improved drivers into Kalman filter • For longer-term, must forecast or measure upstream drivers/couplings Space Weather Workshop 2008, Boulder, CO

  3. State and covariance Analysis State and covariance Forecast Adjustment Of Parameters Kalman Filter 4DVAR Global Assimilative Ionospheric Model Data Assimilation Process Driving Forces Physics Model Mapping State To Measurements Innovation Vector • Kalman Filter • Recursive Filtering • Covariance estimation and state correction Optimal interpolation Band-Limited Kalman filter • 4-Dimensional Variational Approach • Minimization of cost function by estimating driving parameters • Non-linear least-square minimization • Adjoint method to efficiently compute the gradient of cost function • Parameterization of model “drivers” Space Weather Workshop 2008, Boulder, CO

  4. Forward Model with an Adjoint • Driver Models • NRL MSIS, HWM, Fejer-Scherliess ExB Drift (Fortran) • Eulerian Solver • Variable-resolution, magnetic grid • Six ions: O+, H+, He+, N2+, O2+, NO+ • Computational Efficiency • Adjoint computes all driver sensitivities in one pass • Assim. cycle: Run forward model once & adjoint just once • Multi-level physics cache: • Find in memory, pre-computed file, or generate • Optimized C++ (2nd generation code) • Object-oriented, Templated Matrix classes • High-performance numerics • Kudos to our C++ expert, Vardan Akopian Space Weather Workshop 2008, Boulder, CO

  5. State and covariance Analysis State and covariance Forecast Adjustment Of Parameters Kalman Filter 4DVAR Global Assimilative Ionospheric Model Data Assimilation Process Driving Forces Physics Model Mapping State To Measurements Innovation Vector • Kalman Filter • Recursive Filtering • Covariance estimation and state correction Optimal interpolation Band-Limited Kalman filter • 4-Dimensional Variational Approach • Minimization of cost function by estimating driving parameters • Non-linear least-square minimization • Adjoint method to efficiently compute the gradient of cost function • Parameterization of model “drivers” Space Weather Workshop 2008, Boulder, CO

  6. JPL/USC GAIM++ Forward Model With Adjoint 4DVAR Kalman Filter Space Weather Workshop 2008, Boulder, CO

  7. Optimization Approach: 4DVAR • Non-linear least squares minimization • Cost functionto compute model deviation from observations • Adjoint method to compute gradient of cost function: computational efficiency • Minimization:finding roots using Newton’s method by estimating driving parameters • Parameterizationof model drivers Estimate ionospheric drivers & optimize state Space Weather Workshop 2008, Boulder, CO

  8. Better Drivers => Better Forecast • Observation System Simulation Experiments (OSSE) to estimate “perturbed” drivers at low latitudes: • Neutral winds • EB vertical drift velocity • Production terms • Synthetic ground GPS TEC data Space Weather Workshop 2008, Boulder, CO

  9. JPL/USC Real-Time GAIM: RT TEC Map & Density SlicesThree Installations: JPL, AFRL, DoD Space Weather Workshop 2008, Boulder, CO

  10. Outline • Global Assimilative Ionosphere Model (GAIM) • First-principles physics model, with an adjoint • Assimilation by Kalman filter and 4DVAR • Assimilating COSMIC TEC improves profile shapes • Three case studies: Arecibo, Jicamarca and Millstone ISR • Extensive validation using Jason VTEC, ISR profiles, ionosonde • Storm Studies • TEC and density profile perturbations during August 7, 2006 storm • Ray Tracing Capability Added to GAIM • Trace ray bending thru 3D electron density field • Application: Improving neutral atmosphere retrievals from COSMIC • Short-Term Forecast (2-6 hours) • Adjust drivers using 4DVAR; feed improved drivers into Kalman filter • For longer-term, must forecast or measure upstream drivers/couplings Space Weather Workshop 2008, Boulder, CO

  11. GAIM Input Data Types • Ground GPS Data (Absolute TEC) • >150 5-min. to Hourly Global GPS Ground Stations • Assimilate >300,000 TEC points per day (@ 5 min rate) per day • Space GPS Data (Relative TEC) • CHAMP (@ 440 km) • SAC-C (@ 700 km) • IOX (@ 800 km) • GRACE (@ 350 km) • Topex/Poseidon (@1330 km) (Upward looking only) • Jason 1 (@1330 km) (Upward looking only) • C/NOFS & COSMIC constellation • UV Airglow: Limb & Nadir Scans • LORAAS on ARGOS, GUVI on TIMED • SSUSI/SSULI on DMSP and NPOESS • Other Data Types • TEC from TOPEX & JASON Ocean Altimeters • Ionosonde • DMSP, CHAMP, C/NOFS in situ density • C/NOFS Electric fields • GRACE Cross links • ISR Space Weather Workshop 2008, Boulder, CO

  12. Low-Earth Orbiter GPS COSMICIonospheric Weather Constellation Electron Density Profile COSMIC coverage: 2500 profiles/day Six-satellite COSMIC constellation Launched April 14, 2006 Space Weather Workshop 2008, Boulder, CO

  13. Occultation TEC Links Space Weather Workshop 2008, Boulder, CO

  14. Kalman Assimilation Runs: Three Case Studies (Attila Komjathy) • Three runs: • GAIM Climate (no data) • Ground GPS TEC (200 sites) • Ground + COSMIC links • (upward & occultation) • Medium and Low Resolution runs: • 2.5 Vs. 5.0 Lat. In Deg. • 10.0 Vs. 15.0 Lon. in Deg. • 40 Vs. 80 Alt. in km • 100,000 Vs. 18,000 voxels • Sparse Kalman filter: • Update & propagate covariance • Truncate off-diagonal covariance • that is beyond physical correlation • lengths Eccentric tilted dipole Magnetic equator Intersections of : - magnetic field lines, - magnetic geopotential lines - and magnetic longitudes Space Weather Workshop 2008, Boulder, CO

  15. Case 1: Arecibo ISR Study for June 26, 2006 FM2 20:09 20:05 UT 20:00 SCUB CRO1 UT 20:00 GPS15 Arecibo FM5 20:25 20:21 JAMA CRO1 UT 20:12 UT 20:24 Space Weather Workshop 2008, Boulder, CO

  16. GAIM versus Abel Profiles Space Weather Workshop 2008, Boulder, CO

  17. UCAR and JPL Raw GPS Data Processing Results for Sept 21, 2006 Comparison of UCAR and JPL calibrated TEC near Jicamarca Ground and COSMIC ground tracks near Jicamarca Ground and COSMIC data availability near Jicamarca Space Weather Workshop 2008, Boulder, CO

  18. An Example of COSMIC Impact on Profile Shape 1. UT 15:24 2. UT 15:48 1. UT 15:36 COSMIC UT 15:30 3. UT 16:36 Elevation angle 1. 2. 3. UT hours Space Weather Workshop 2008, Boulder, CO

  19. Illustration for TEC data, GAIM Prefit and Postfit Residuals Space Weather Workshop 2008, Boulder, CO

  20. TEC Comparison with Jicamarca ISR Space Weather Workshop 2008, Boulder, CO

  21. NmF2 Comparison with Jicamarca ISR Medium resolution GAIM NmF2 with COSMIC data matches well during the dense data period 11-17 UT Space Weather Workshop 2008, Boulder, CO

  22. HmF2 Comparison with Jicamarca ISR Medium resolution GAIM HmF2 with COSMIC matches best with truth Space Weather Workshop 2008, Boulder, CO

  23. Summary of Results TEC NmF2 Space Weather Workshop 2008, Boulder, CO

  24. Summary of Results GO = Ground-GPS only GD = Ground + down-looking COSMIC Space Weather Workshop 2008, Boulder, CO

  25. GAIM w/ COSMIC versus JASON VTEC Space Weather Workshop 2008, Boulder, CO

  26. Detail for JASON Track off Australiaon 06/26/2006 Nearby COSMIC data crucial for achieving accuracy. Space Weather Workshop 2008, Boulder, CO

  27. GAIM w/ COSMIC versus JASON VTEC Statistics over Three ISR Periods Space Weather Workshop 2008, Boulder, CO

  28. GAIM Driven By Ground GPS Onlyversus JASON VTEC June – Nov. 2004: 137 days Space Weather Workshop 2008, Boulder, CO

  29. Outline • Global Assimilative Ionosphere Model (GAIM) • First-principles physics model, with an adjoint • Assimilation by Kalman filter and 4DVAR • Assimilating COSMIC TEC improves profile shapes • Three case studies: Arecibo, Jicamarca and Millstone ISR • Extensive validation using Jason VTEC, ISR profiles, ionosonde • Storm Studies (Xiaoqing Pi) • TEC and density profile perturbations during August 7, 2006 storm • Ray Tracing Capability Added to GAIM • Trace ray bending thru 3D electron density field • Application: Improving neutral atmosphere retrievals from COSMIC • Short-Term Forecast (2-6 hours) • Adjust drivers using 4DVAR; feed improved drivers into Kalman filter • For longer-term, must forecast or measure upstream drivers Space Weather Workshop 2008, Boulder, CO

  30. Drivers of the Ionosphere: Coupling with Magnetosphere and Thermosphere Solar EUV radiation Cause of the ionization Solar flares Auroral particle precipitation Cause of the ionization at high latitudes Significant variations during storms and substorms Thermospheric composition & temperature Gas to be ionized Loss of ionization due to chemical reactions Global thermospheric circulation changes during storms Dynamics Electric fields: originated from the magnetospheric and wind dynamo processes Thermospheric winds Controlled by the geomagnetic field Magnetospheric convection, penetration, and disturbance wind dynamo Ionospheric data assimilation combines first-principles physics-based modeling and global-scale observations. For long-term forecast of ionospheric weather, must deal with the drivers and magnetospheric & thermospheric couplings. Space Weather Workshop 2008, Boulder, CO

  31. Magnetic Storm: August 7, 2006 AUG 4 AUG 5 AUG6 AUG 7 AUG 8 AUG 9 AUG 10 AUG11 100 nT -80 nT Space Weather Workshop 2008, Boulder, CO

  32. Global Ionospheric Maps 04:00 & 07:15 UT Space Weather Workshop 2008, Boulder, CO

  33. Global Ionospheric Maps: 10:30 & 23:00 UT Space Weather Workshop 2008, Boulder, CO

  34. Validation of GAIM Using JASON Altimeter TEC Measurements TEC along Jason orbit tracks Storm Day Statistics for the entire day GPS ground stations Tracks of COSMIC occul. tangent points Jason orbit tracks Space Weather Workshop 2008, Boulder, CO

  35. COSMIC RO and JASON Comparison Comparisons between GAIM, IRI, and Jason ~ 1 hour Space Weather Workshop 2008, Boulder, CO

  36. Disturbed Ionosphere at 9 UT TEC perturbations in the west Pacific longitudes COSMIC coverage in the regions of perturbations Space Weather Workshop 2008, Boulder, CO

  37. Ne Disturbance in the Pacific Longitudes Space Weather Workshop 2008, Boulder, CO

  38. Disturbed Ionosphere at 10 UT TEC perturbations in the west Pacific longitudes COSMIC coverage in the regions of perturbations Space Weather Workshop 2008, Boulder, CO

  39. Ne Disturbance in the Pacific Longitudes Space Weather Workshop 2008, Boulder, CO

  40. Outline • Global Assimilative Ionosphere Model (GAIM) • First-principles physics model, with an adjoint • Assimilation by Kalman filter and 4DVAR • Assimilating COSMIC TEC improves profile shapes • Three case studies: Arecibo, Jicamarca and Millstone ISR • Extensive validation using Jason VTEC, ISR profiles, ionosonde • Storm Studies • TEC and density profile perturbations during August 7, 2006 storm • Ray Tracing Capability Added to GAIM (Chi Ao) • Trace ray bending thru 3D electron density field • Application: Improving neutral atmosphere retrievals from COSMIC • Short-Term Forecast (2-6 hours) • Adjust drivers using 4DVAR; feed improved drivers into Kalman filter • For longer-term, must forecast or measure upstream drivers Space Weather Workshop 2008, Boulder, CO

  41. GAIM++ 3D Raytracing Capability(Chi Ao) 3D grid of Ne GAIM 3D Raytracer Rx/Tx Loc. & Freq TEC, Group path Magnetic field • Adaptive Runge-Kutta solver • Tricubic interpolation of electron density in (r,lat,lon) space [Lekien et al., 2004] • IGRF magnetic field • Refractive index from Appleton-Hartree formula • “Homing” using the Subplex algorithm (generalization of the Nelder-Mead simplex method) [Rowan, 1990] Group path Ionosphere: Space Weather Workshop 2008, Boulder, CO

  42. Elevation Angles and Homing Geometric Path True Path Non-Homing Path STECNonhome> STECTrue> STECGeo Space Weather Workshop 2008, Boulder, CO

  43. Bending for Trans-Iono Raypaths 200 Mhz 30 Mhz 50 Mhz L1 See expected behavior: Much more bending at low frequencies Space Weather Workshop 2008, Boulder, CO

  44. Effect on Atmospheric Temperature Retrieval Space Weather Workshop 2008, Boulder, CO

  45. Error Study: Large-Scale Ionosphere Receiver 11-year solar cycle Transmitter L2 L1 “Ionosphere-free” linear combination Note: no assumptions made about ionospheric structure Space Weather Workshop 2008, Boulder, CO

  46. Magnitude of Different Effects From Bassiri and Hajj, 1993 Space Weather Workshop 2008, Boulder, CO

  47. Bending Along L1 & L2 Signal Paths Need accuracy to 0.05 % in refractivity to get 0.1 degrees K. Space Weather Workshop 2008, Boulder, CO

  48. Effect on Atmospheric Temperature Retrieval Space Weather Workshop 2008, Boulder, CO

  49. Short-Term Forecast Issues • Start with accurate iono. nowcast from data assimilation • Exploit all global datasets, quantitative accuracy demonstrated • Lots of science can be done with accurate 3D density fields • Estimate improved drivers using 4DVAR • Drivers: production, ExB drift, neutral winds, etc. • Feed improved drivers into Kalman filter • Forecast for 2-6 hours using physics propagator • Continuous Forecast Validation Needed • Unknown drivers or couplings drive iono. physics away from reality • Simplest Benchmark: Must beat persistence • Community should start comparing Skill Scores • Iono. Assim. Complementary to T-I-M Coupled Models • Couplings still incomplete, not quantitatively accurate, enough data? • Use 4DVAR to invert for coupled boundary conditions Space Weather Workshop 2008, Boulder, CO

  50. Summary • Global Assimilative Ionosphere Model (JPL/USC GAIM) • First-principles physics model, with an adjoint • Assimilation by Kalman filter and 4DVAR • Assimilating COSMIC TEC improves profile shapes • Extensive validation using Jason VTEC, ISR profiles, ionosonde • Storm Studies using new level of global 3D accuracy • Quantitatively-accurate science can be done • Ray Tracing Capability Added to GAIM • Looking for new iono. or atmo. applications for ray tracer • Short-Term Forecast (2-6 hours) • Adjust drivers using 4DVAR; feed improved drivers into Kalman filter • High accuracy iono. forecast beyond 6 hours is HARD. • Many approaches to 12-72 hour forecast should be investigated. Space Weather Workshop 2008, Boulder, CO

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