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Summary of modification surface data assimilation code

This summary presents modifications made to the surface data assimilation code utilized by the Central Weather Bureau in Taiwan. Key updates are discussed, including improvements in tangent linear and adjoint code correctness checks. The modified code has shown better performance in low and mid-level forecasts during a one-month experiment period. Various modifications are highlighted, confirming their effectiveness through rigorous correctness checks and performance analyses. The results indicate that the new code yields superior outcomes compared to the original in various atmospheric parameters.

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Summary of modification surface data assimilation code

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  1. Summary of modification surface data assimilation code Chin-Hsiao Chiang Central Weather Bureau , Taiwan Acknowledgement : Yong-Run, Guo Chien-Han, Tseng

  2. Which codes need to modify or develop ? • da_sfc_wtq.inc • da_transform_xtowtq.inc • da_sfc_wtq_lin.inc • da_transform_xtowtq_adj.inc • da_sfc_wtq_adj.inc • da_transfer_wrftoxb.inc • da_transfer_xatowrf.inc • Tangent linear correctness check code • Adjoint correctness check code

  3. Correctness (or tangent linear validation) check From Y.-R. Guo From Taylor expansion, set , we can obtain Where is a parameter, and is a constant vector. When is small enough, but larger than the machine accuracy, the values of should be very close to 1.0 if the tangent linear code is correct. If the values of is not close to 1.0 with small , the tangent linear code is incorrect (or invalid). In the correctness check, the Fortran compiler must be with the option –r8.

  4. Tangent Linear correctness check (U10) original modify Accu. Close to 1

  5. Tangent Linear correctness check (T2) original modify Accu. Close to 1

  6. Adjoint Correctness check From Y.-R. Guo where is the arbitrary perturbation vector, is the tangent linear operator, and is the adjoint operator. Note: There is no approximation from TLM to Adjoint, the correctness check must have ’13-digit same’ accuracy for 64-bit data (with the compiler option –r8). Otherwise, the adjoint code is wrong.

  7. Results of adjoint code correctness check Check ALL: point( 80, 56), regime= 2.10 lefttotal=0.24450237286068E+03 righttotal=0.24450237286068E+03 Check ALL: point( 76, 58), regime= 3.10 lefttotal=0.25384163468517E+03 righttotal=0.25384163468517E+03 Check ALL: point(130, 61), regime= 4.10 lefttotal=0.28047614377858E+03 righttotal=0.28047614377858E+03 Check ALL: point(131, 98), regime= 1.10 lefttotal=0.27966553760352E+03 righttotal=0.27966553760352E+03 Check ALL: point( 80, 56), regime= 2.10 lefttotal=0.24450237296108E+03 righttotal=0.24450237296108E+03 Check ALL: point( 76, 58), regime= 3.10 lefttotal=0.25384163474149E+03 righttotal=0.25384163474149E+03 Check ALL: point(130, 61), regime= 4.10 lefttotal=0.28044525500909E+03 righttotal=0.28044525500909E+03 Check ALL: point(131, 98), regime= 1.10 lefttotal=0.27966553762444E+03 righttotal=0.27966553762444E+03 original modify Left = Right Left = Right

  8. Case2009060818

  9. 500 hPa Geopotential Height & Temperature original modify Trough still exist

  10. 500 hPa Horizontal Wind Vectors original modify

  11. Sea Level Pressure original modify

  12. Experiments • WPS & WRF version : V3.1 (OP211) • WRFDA version : V3.2.1 • Period : 2009060100 ~ 2009063012 (one month) • Verify against NCEP analysis • Experiments : OP211321 (WRFDA V3.2.1) • OP211321S (WRFDA V3.2.1 + modify sfc code) • No assimilate GPSRO • Only Domain 1 • Two experiments are running smoothly • In official release WRFDA V3.2.1 version, surface pressure came from wrfinput already.

  13. analysis

  14. OP211321 OP211321S RMS of H Anomaly Correlation of H Modify sfc code got better result than original code in low and mid level

  15. OP211321 OP211321S RMS of T RMS of U Modify sfc code got better result than original code in low and mid level

  16. 24 hr

  17. OP211321 OP211321S RMS of H RMS of T

  18. OP211321 OP211321S RMS of U RMS of V

  19. 48 hr

  20. OP211321 OP211321S RMS of H RMS of T

  21. OP211321 OP211321S RMS of U RMS of V

  22. 72 hr

  23. OP211321 OP211321S RMS of H RMS of T

  24. OP211321 OP211321S RMS of U RMS of V

  25. O : original M : Modified Statistics “Green” means modified better than original Overall, Modified sfc code got better result from analysis to 72hr forecast

  26. 2D Analysis monthly mean

  27. Red : original Blue : modified Green : Ncep

  28. Red : original Blue : modified Green : Ncep

  29. Summary • After Tangent Linear and Adjoint code correctness checking , the modification procedure is right. • In single case (2009060818), modified and original code got very similar results, the trough at Guangzhou still exist. • Results of one month experiment from grid verification : analysis : • Modified sfc code got better results (H,T,U,V) at low and mid levels. forecast : • Modified sfc code got slightly better “T” at full levels until 72 hr forecast. • Modified sfc code got slightly better “U” at low and mid levels until 72 hr forecast. • Modified sfc code got slightly better “H” at mid and upper levels until 72 hr forecast.

  30. Horizontal distribution of monthly mean, can’t know which one is better.

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