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CMP Model Effects on ILRS Products

This paper examines the modifications made to the Conventional Mean Pole (CMP) model and their impact on ILRS products. It discusses the changes introduced to the CMP model and their implications for SLR data analysis.

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CMP Model Effects on ILRS Products

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  1. CMP Model Effects on ILRS Products E. C. Pavlis and M. Kuzmicz-Cieslak 2017 IERS Unified Analysis Workshop 10-12 July 2017, Paris, France

  2. Introduction • The Conventional Mean Pole (CMP) model has been provided by the IERS Conventions in a linear form since the 2003 edition. • In the 2010 release, the model was initially modified to a cubic one with a linear extrapolation after 2010.0. • By 2015, publications of present-day ice sheet mass losses led to a further modification that directed the users to use: • either a tabular form stored in an online file and maintained by the IERS EOP Center, or • a yearly updated subroutine that essentially reproduced*the tabular data. • The IERS routine was never updated for the current year, and so the Services had no way to use it and were left with the tabular data as the only option. • Several users had noticed that the online tabular data files were being changed without prior notification to the users, which led to a study of some of the versions that were captured at various times to determine the level and the nature of variations introduced. *Which could not track of course the changes in the online tables! 2017 IERS UAW, Paris, France

  3. IERS 2010 Conventions Update Chapter 7, section 7.1.4 2017 IERS UAW, Paris, France

  4. Rapid ice melting drives Earth's pole to the eastJ. L. Chen1, C. R. Wilson1,2, J. C. Ries1, B. D. Tapley1DOI: 10.1002/grl.50552 GEOPHYSICAL RESEARCH LETTERS, VOL. 40, 2625–2630, doi:10.1002/grl.50552, 2013 2017 IERS UAW, Paris, France

  5. Climate-driven Polar Motion: 2003-2015 S. Adhikari & Erik R. Ivins/JPLSci. Adv. 2016;2:e1501693 8 April 2016 2017 IERS UAW, Paris, France

  6. Climate-driven Polar Motion: 2003-2015 S. Adhikari & Erik R. IvinsJPL 2017 IERS UAW, Paris, France

  7. IERS CMP Plots Online Downloaded: 2016.05.17 Downloaded: 2016.09.27 2017 IERS UAW, Paris, France

  8. IERS CMP Comparison 2017 IERS UAW, Paris, France

  9. IERS CMP Comparison - detail 2017 IERS UAW, Paris, France

  10. CMP Differences of IERS Updates These modifications of the series in the special table “mean-pole.tab” were not announced and to this point no one has documented anywhere that they ever happened. Unless someone checked the file often, we do not know how many times it was changed. 2017 IERS UAW, Paris, France

  11. CMP Test Experiment with SLR Data • The ILRS contribution to the ITRF2014 used one of the recent CMP tables as the basis for our data reduction (v70). • In order to get a measure of the effect the CMP definition will have on our products, we adopted the 2003-type CMP, using the values proposed by J. C. Ries (see his earlier presentation): • Xp = 55.0 + (t – 2000)*1.677 [mas] • Yp= 320.5 + (t – 2000)*3.460 [mas] • t is in years • We reanalyzed the period Jan. 1, 2016 to present. • Although no other changes were made in the modeling of the data, the RMS of the weekly arcs used was systematically lower than the one using the previous CMP model. 2017 IERS UAW, Paris, France

  12. Weekly JCET Solutions –CMP Tests

  13. Weekly JCET Solutions –CMP Tests North Hemisphere South Hemisphere 2017 IERS UAW, Paris, France

  14. Weekly JCET Solutions –CMP Tests Graz Matera Herstmonceux ● OLD CMP ● NEW CMP Yarragadee Hartebeesthoek Mt. Stromlo

  15. CMP Test Experiment with SLR Data • The new analysis (v77) shows a 1 mm drop in the average RMS of fit values. • Comparing the height adjustments with respect to SLRF2014 between the two series, we see a mean of 6.8 mm (OLD-NEW) for the 27 strongest participating sites. • An extended period re-analysis with the new CMP model is in progress, which will include the adjustment of velocities as well as positions. • Results expected by end of summer 2017. 2017 IERS UAW, Paris, France

  16. Weekly JCET Solutions – MP Tests ● OLD CMP ● NEW CMP 2017 IERS UAW, Paris, France

  17. Weekly JCET Solutions – MP Tests ● OLD CMP ● NEW CMP 2017 IERS UAW, Paris, France

  18. Weekly JCET Solutions – MP Tests ● OLD CMP ● NEW CMP 2017 IERS UAW, Paris, France

  19. Weekly JCET Solutions – MP Tests ● OLD CMP ● NEW CMP 2017 IERS UAW, Paris, France

  20. Weekly JCET Solutions – MP Tests ● OLD CMP ● NEW CMP 2017 IERS UAW, Paris, France

  21. Weekly JCET Solutions – MP Tests ● OLD CMP ● NEW CMP 2017 IERS UAW, Paris, France

  22. Weekly JCET Solutions –CMP Tests North Hemisphere South Hemisphere Sorted in Longitude 2017 IERS UAW, Paris, France

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