Fourth European Space Weather Week
5-9 Nov. 2007
TEC FORECASTING DURING DISTURBED
SPACE WEATHER CONDITIONS:
A POSSIBLE ALTERNATIVE TO THE IRI-2001
Yurdanur Tulunay1, Erdem Turker Senalp2, Ersin Tulunay2
(1)
ODTU / METU Ankara, TURKEY
Dept. of Aerospace Eng., [email protected]
(2) Dept. of Electrical and Electronics Eng.
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CONTENTS
1. Introduction
2. METU-NN-C
3. Data Organisation
4. Results
5. Conclusions
6. Acknowledgements
7. References
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INTRODUCTION
Ionospheric processes:
highly nonlinear and dynamic
TEC:
key parameter in navigation
and telecommunication
METU Group:
specialized on data driven
modelling since 1990’s
Recently developped:
NN and Cascade Model based
on the Hammerstein system
modelling
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Objective:
•
to forecast TEC with higher accuracy under the
influence of the extreme solar events.
A case study: Solar Events of April 2002
•
A possible alternative to IRI-2001?
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Why and How?
• Mathematical models of the ionospheric parameters
(i.e. TEC) DIFFICULT
• Data-driven approaches (i.e. NN modelling)
employed in parallel with the mathematical models
• Therefore, METU-NN-C using Bezier curves to represent
nonlinearities
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METU-NN-C
•
TEC map over Europe constructed by METU-NN in
2004 and 2006 (Tulunay et al. [2004a, 2006] )
•
to increase the performance, a new technique,
METU-NN-C developped [Senalp, 2007]
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1
2
Fig. 1. Construction of the METU-NN-C Models
3
[Senalp et al., 2007]
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k
: Discrete time index
uDp(k) : Inputs
xDq(k) : the internal variables of the METU-C
Block 1:
METU-NN model estimates the state-like variables for
the METU-C
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Block 2:
Construction of Nonlinear Static Block of
METU-C
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Block 3:
Construction of Linear Dynamic Block of
METU-C
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The Generic METU-NN-C Model
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Phases of Application of METU-NN-C:
•
•
‘Training’
‘Test’
Inputs:
• Present value of TEC: TEC(k)
• Temporal parameters: Trigonometric comp. of time
Bezier curves to represent NONLINEARITIES
METU-NN: State-like variable estimator
Output:
• Forecast TEC values one hour in advance
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DATA ORGANIZATION
• 10-min GPS-TEC data of
Chilbolton (51.8˚N; 1.26˚W)
Hailsham (50.9˚N; 0.3˚E)
• Development Step:
Training:
Chilbolton TEC
Validation:
Chilbolton TEC
(April; May 2000, 2001)
(April-May 2000, 2001)
• Operation Step:
Validation:
Hailsham TEC (April; May 2002)
• 2000-2002 SSN max. years
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RESULTS
Fig. 2 Observed and one hour ahead Forecast Hailsham TEC values for April, May
2002 [Senalp et al., 2007]
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Fig. 3. METU-NN-C and IRI-2001 during disturbed conditions (Hailsham)
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METU-NN-C
IRI-2001
- Fig. 4. Scatter diagrams and best-fit lines: in 18-19 April 2002 at Hailsham
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Table 1. Performance of models
(18-19 April 2002; Hailsham)
Normalized Error (%)
Cross Correlation Coefficient (x10-2)
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METU-NN-C
20.04
98.7
IRI-2001
204.1
83.8
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CONCLUSIONS
• During disturbed SW conditions, METU-NN-C seems to
show better performance over IRI-2001
• METU-NN-C Model - more versatile and has got
advantages provided that the representative data are
available
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Acknowledgements
This work is partially supported by
• EU action of COST 296 (Mitigation of Ionospheric Effects on Radio
Systems)
• TUBITAK-ÇAYDAG (105Y003)
• GPS-TEC data are kindly provided by Dr. Lj. R. Cander
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