1. Making sense of SuperDARN elevation: Phase offset and variance
Pasha Ponomarenko, Jan Wiid, Sasha Koustov,
and Jean-Pierre St.-Maurice
University of Saskatchewan, CANADA
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

2. SuperDARN Workshop, 29 May - 3June 2011, Hanover, US
Abstract
The vertical angle of arrival of HF signals contains very important information about the propagation modes and ionospheric conditions. However, despite being routinely registered by SuperDARN radars, elevation angles are rarely utilised. The main reason for that is the apparent unreliability of these data, which frequently appear to be unrealistic. At SuperDARN’2010 we attributed the problem to an inadequate phase calibration that fails to account for certain phase shifts in the radar hardware. However, a following detailed analysis of the experimental data and statistical modelling revealed that the presence of “strange” elevation components could be fully explained by accounting for the statistical distribution of phase fitting errors. In essence, a combination of this distribution with the very non-linear phase-elevation relationship leads to a two-pi wrap-around of the phase that results in an artificial population of echoes at very high elevation angles.
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

3. SuperDARN Workshop, 29 May - 3June 2011, Hanover, US
Outline
Introduction
Apparent problems
Phase calibration
Fitting error effects
Conclusions
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

4. Definition and importance
Elevation angle – vertical angle of arrival of HF signal
Diagnostic importance:
HF propagation mode
ionospheric plasma density (Secant Law)
n <1
n = 1 h x
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

5. SuperDARN Interferometry d' 2π
max
Ψmax
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

6. Elevation vs phase shift
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

7. Suspiciously high values
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

8. Split phase distribution?
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

9. All ranges @ multiple frequencies
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

10. SuperDARN Workshop, 29 May - 3June 2011, Hanover, US
Phase offset?
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

11. SuperDARN Workshop, 29 May - 3June 2011, Hanover, US
Phase calibration
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

12. SuperDARN Workshop, 29 May - 3June 2011, Hanover, US
Calibrated elevation
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

13. Still does not look right...
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

14. What about phase fitting errors?
 0 Δ σ 
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

15. One-sigma fitting error from data
median  8 deg
mean  6 deg
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

16. Modelling: phase variance effect
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

17. SuperDARN Workshop, 29 May - 3June 2011, Hanover, US
So, SOME flipping is OK!
Calibrated
Raw
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US

18. SuperDARN Workshop, 29 May - 3June 2011, Hanover, US
Concluisons
If after phase calibration the maximum of the phase distribution at any given range does not flip over to the high elevation end, the elevation data should be OK.
Now, how can we utilise elevation?
See the follow-up talk on Wednesday!
31 December, 2018
SuperDARN Workshop, 29 May - 3June 2011, Hanover, US