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ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 1
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: [email protected]
Brian Wilson, Attila Komjathy, Vardan Akopian,Brian Wilson, Attila Komjathy, Vardan Akopian,Xioaqing Pi, Chi Ao, and Byron IijimaXioaqing Pi, Chi Ao, and Byron Iijima
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 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
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 3
Global Assimilative Ionospheric ModelGlobal Assimilative Ionospheric ModelData Assimilation ProcessData Assimilation Process
DrivingForces
DrivingForces
Mapping State To Measurements
Mapping State To Measurements
PhysicsModel
PhysicsModel
Kalman FilterKalman Filter
State and covariance
Forecast
State andcovarianceAnalysis
AdjustmentOf Parameters
4DVAR4DVAR
Innovation Vector
• Kalman Filter• Recursive Filtering• Covariance estimation and state
correctionOptimal interpolationBand-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”
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 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
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 5
Global Assimilative Ionospheric ModelGlobal Assimilative Ionospheric ModelData Assimilation ProcessData Assimilation Process
DrivingForces
DrivingForces
Mapping State To Measurements
Mapping State To Measurements
PhysicsModel
PhysicsModel
Kalman FilterKalman Filter
State and covariance
Forecast
State andcovarianceAnalysis
AdjustmentOf Parameters
4DVAR4DVAR
Innovation Vector
• Kalman Filter• Recursive Filtering• Covariance estimation and state
correctionOptimal interpolationBand-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”
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 6
JPL/USC GAIM++JPL/USC GAIM++
Forward ModelWith Adjoint
4DVAR Kalman Filter
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 7
Optimization Approach: 4DVAR
• Non-linear least squares minimization• Cost function to 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
• Parameterization of model drivers
Estimate ionospheric drivers & optimize state
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ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 8
Better Drivers => Better Forecast
• Observation System Simulation Experiments (OSSE) to estimate “perturbed” drivers at low latitudes:
• Neutral winds
• EB vertical drift velocity
• Production terms
• Synthetic ground GPS TEC data
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 11
JPL/USC Real-Time GAIM: RT TEC Map & Density SlicesThree Installations: JPL, AFRL, DoD
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 12
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
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 13
GAIM Input Data TypesGAIM Input Data TypesGAIM Input Data TypesGAIM 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 ScansLORAAS on ARGOS, GUVI on TIMEDSSUSI/SSULI on DMSP and NPOESS
• Other Data TypesTEC from TOPEX & JASON Ocean AltimetersIonosondeDMSP, CHAMP, C/NOFS in situ densityC/NOFS Electric fieldsGRACE Cross linksISR
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 15
Six-satellite COSMIC constellationLaunched April 14, 2006
Low-Earth OrbiterGPS
ElectronDensityProfile
COSMIC coverage: 2500 profiles/day
COSMICCOSMICIonospheric Weather ConstellationIonospheric Weather Constellation
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 17
Occultation TEC Links
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 18
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
Magnetic equatorEcc
en
tric
tilt
ed
dip
ole
Intersections of :- magnetic field lines, - magnetic geopotential lines- and magnetic longitudes
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 19
Arecibo
FM2
FM5GPS15
20:0520:09
20:21
20:25
CRO1
JAMA
SCUB CRO1
UT 20:00
Case 1: Arecibo ISR Study for June 26, 2006
UT 20:00
UT 20:12 UT 20:24
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 20
GAIM versus Abel ProfilesGAIM versus Abel Profiles
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 23
UCAR and JPL Raw GPS Data Processing UCAR and JPL Raw GPS Data Processing Results for Sept 21, 2006Results for Sept 21, 2006
Comparison of UCAR and JPLcalibrated TEC near Jicamarca
Ground and COSMIC data availability near Jicamarca
Ground and COSMIC ground tracks near Jicamarca
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 24
An Example of COSMIC Impact on Profile ShapeAn Example of COSMIC Impact on Profile Shape
2. UT 15:48
3. UT 16:36COSMIC UT 15:30
UT hours
Ele
vatio
n an
gle
1. UT 15:24
1. 2. 3.
1. UT 15:36
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 25
Illustration for TEC data, GAIM Prefit and Postfit Illustration for TEC data, GAIM Prefit and Postfit ResidualsResiduals
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 27
TEC Comparison with Jicamarca ISRTEC Comparison with Jicamarca ISR
GAIM Medium Resolution Assimilation Results for Sept 21, 2006
0
5
10
15
20
25
30
35
0 2 4 6 8 10 12 14 16 18 20 22 24 26UT in Hours
TEC in T
ECU
JRO: Jicamarca ISR
medium resolution climate
medium resolution ground-only assimilation
medium resolution ground+COSMIC assmilation
COSMIC Data
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 28
NmF2 Comparison with Jicamarca ISRNmF2 Comparison with Jicamarca ISR
Medium resolution GAIM NmF2 with COSMIC data matches well during the dense data period 11-17 UT
GAIM Medium Resolution Assimilation Results for Sept 21, 2006
0
1E+11
2E+11
3E+11
4E+11
5E+11
6E+11
7E+11
8E+11
9E+11
1E+12
0 2 4 6 8 10 12 14 16 18 20 22 24
UT in Hours
Nm
F2
JRO: Jicamarca ISRmedium resolution climatemedium resolution ground-only assimilationmedium resolution ground+COSMIC assimilation
COSMIC Data
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 29
HmF2 Comparison with Jicamarca ISRHmF2 Comparison with Jicamarca ISR
GAIM Medium Resolution Assimilation Results for HmF2 on Sept 21, 2006
0
50
100
150
200
250
300
350
400
450
0 2 4 6 8 10 12 14 16 18 20 22 24
UT in Hours
Hm
F2
JRO: Jicamarca ISRmedium resolution climatemedium resolution ground-only assimilationmedium resolution ground+COSMIC assimilation
COSMIC Data Available
Medium resolution GAIM HmF2 with COSMIC matches best with truth
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 30
Summary of ResultsSummary of ResultsTEC Comparison of Low and Medium Resolution Runs for Sept 21, 2006
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Climate Low GO Low G+C Medium GO Medium G+C
TE
C i
n T
EC
U
Abs Mean
Sigma
NmF2 Comparison of Low and Medium Resolution Runs for Sept 21, 2006
0.00E+00
1.00E+10
2.00E+10
3.00E+10
4.00E+10
5.00E+10
6.00E+10
7.00E+10
8.00E+10
9.00E+10
1.00E+11
Climate Low GO Low G+C Medium GO Medium G+C
Ele
ctr
on
De
nsit
y
Abs Mean
Sigma
TEC
NmF2
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 31
Summary of ResultsSummary of Results
HmF2 Comparison of Low and Medium Resolution Runs for Sept 21, 2006
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
Climate Low GO Low G+C Medium GO Medium G+C
He
igh
t in
Km
Abs Mean
Sigma
GO = Ground-GPS only GD = Ground + down-looking COSMIC
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 36
GAIM w/ COSMIC versus JASON VTECGAIM w/ COSMIC versus JASON VTEC
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 37
Detail for JASON Track off AustraliaDetail for JASON Track off Australiaon 06/26/2006on 06/26/2006
Nearby COSMIC data crucial for achieving accuracy.
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 38
Mean Sigma RMS
GIM -1.61 2.88 3.31
06/26/06 Ground -0.24 3.26 3.27
Ground+COSMIC -0.29 2.26 2.28
Mean Sigma RMS
GIM -2.01 3.48 4.02
09/21/06 Ground -1.08 3.45 3.62
Ground+COSMIC -0.31 2.66 2.67
Mean Sigma RMS
GIM -1.95 2.58 3.24
12/21/06 Ground -1.3 4.32 4.51
Ground+COSMIC 0.49 2.45 2.54
GAIM w/ COSMIC versus JASON VTECGAIM w/ COSMIC versus JASON VTEC
Statistics over Three ISR Periods
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 39
GAIM Driven By Ground GPS OnlyGAIM Driven By Ground GPS Onlyversus JASON VTECversus JASON VTEC
June – Nov. 2004: 137 days
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 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 (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
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 41
Drivers of the Ionosphere: Drivers of the Ionosphere: Coupling with Magnetosphere and ThermosphereCoupling 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.
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 42
Magnetic Storm: August 7, 2006Magnetic Storm: August 7, 2006
AUG 4 AUG 5 AUG6 AUG 7 AUG 8 AUG 9 AUG 10 AUG11
100 nT
-80 nT
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 43
Global Ionospheric Maps 04:00 & 07:15 UTGlobal Ionospheric Maps 04:00 & 07:15 UT
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 44
Global Ionospheric Maps: 10:30 & 23:00 UTGlobal Ionospheric Maps: 10:30 & 23:00 UT
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 45
Validation of GAIM Validation of GAIM Using JASON Altimeter TEC MeasurementsUsing JASON Altimeter TEC Measurements
Storm Day
Tracks of COSMIC occul. tangent points
Jason orbit tracks
GPS ground stations
Statistics for the entire day
TEC along Jason orbit tracks
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 46
COSMIC RO and JASON ComparisonCOSMIC RO and JASON Comparison
~ 1 hour
Comparisons between GAIM, IRI, and Jason
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 48
Disturbed Ionosphere at 9 UTDisturbed Ionosphere at 9 UT
TEC perturbations in the west Pacific longitudes
COSMIC coverage in the regions of perturbations
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 49
Ne Disturbance in the Pacific LongitudesNe Disturbance in the Pacific Longitudes
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 50
TEC perturbations in the west Pacific longitudes
COSMIC coverage in the regions of perturbations
Disturbed Ionosphere at 10 UTDisturbed Ionosphere at 10 UT
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 51
Ne Disturbance in the Pacific LongitudesNe Disturbance in the Pacific Longitudes
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 52
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
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 53
GAIM++ 3D Raytracing CapabilityGAIM++ 3D Raytracing Capability(Chi Ao)(Chi Ao)
• 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]
3D grid of Ne
Rx/Tx Loc. & Freq
Magnetic field
GAIM3D
RaytracerTEC,
Group path
Group pathIonosphere:
dsvg
dsn
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 54
Elevation Angles and HomingElevation Angles and Homing
Geometric PathGeometric Path
True PathTrue Path
Non-Homing PathNon-Homing Path
STECNonhome > STECTrue > STECGeo
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 55
Bending for Trans-Iono RaypathsBending for Trans-Iono Raypaths
200 Mhz30 Mhz50 Mhz
L1
See expected behavior:Much more bending at low frequencies
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 56
Effect on Atmospheric Temperature RetrievalEffect on Atmospheric Temperature Retrieval
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 57
Error Study: Large-Scale IonosphereError Study: Large-Scale Ionosphere
L1
L2
Transmitter Receiver11-year solar cycle
“Ionosphere-free” linear combination
Note: no assumptions made about ionospheric structure
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 58
Magnitude of Different EffectsMagnitude of Different Effects
From Bassiri and Hajj, 1993
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 59
Bending Along L1 & L2 Signal PathsBending Along L1 & L2 Signal Paths
Need accuracy to0.05 % in refractivityto get 0.1 degrees K.
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 60
Effect on Atmospheric Temperature RetrievalEffect on Atmospheric Temperature Retrieval
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 62
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
ANAS
Space Weather Workshop 2008, Boulder, COApril 29 – May 2, 2008 63
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.