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NOAA Climate Prediction Center Camp Springs, MD 20746 Song.Yang@noaa

Investigating the association between U.S. regional precipitation patterns and circulation conditions using NCEP CFS model. Analyses reveal model strengths and weaknesses across different timescales and regions.

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NOAA Climate Prediction Center Camp Springs, MD 20746 Song.Yang@noaa

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  1. Variability of U.S. Regional Precipitation and Associated Circulation Patterns in the NCEP CFS Song Yang, Yundi Jiang*, Dawei Zheng** Wayne Higgins, Vernon Kousky, and Qin Zhang NOAA Climate Prediction Center Camp Springs, MD 20746 Song.Yang@noaa.gov *CMA National Climate Center, Beijing, China **CAS Shanghai Astronomical Observatory, China

  2. Motivations and Strategies The variations of precipitation on different timescales are associated with different physics and the performance of CFS in simulating these variations is timescale dependent Investigate the time-frequency features of the modeled precipitation and circulation patterns for the timescales of realistic and erroneous simulations to understand the causes of successes and failures

  3. Observations and Model Output Observations *CPC precipitation reconstruction data (Chen et al. 2002) NCEP-NCAR reanalysis winds NOAA extended reconstructed SST CPC Unified precipitation CFS Output *T126 100-year free run T62 50-year free run

  4. Precipitation Diff T62-Obs T126-Obs T126 simulates the annual and seasonal mean precipitation better (than T62)

  5. CN EC IM PW CS SW Diff in Seasonality of Precip (Wash & Lawler 1981) T126-Obs T62-Obs T126 simulates the seasonality of precipitation better (than T62)

  6. Mean Annual Cycle of Regional Precipitation SW

  7. Relations of SW Precip to SST & 850-mb Winds Obs CFS

  8. Obs CFS

  9. Mean Amplitudes and Phases (SW Precipitation)

  10. Relations of SW Precip ANN with SST & 850-mb Winds SW Obs CFS The features associated with the annual cycles of SW precipitation are so different

  11. PW Obs CFS (It is much better for the Pacific West domain!)

  12. Relations of SW Precip Inter-ANN with SST & 850-mb Winds SW Obs CFS CFS also overestimates the interannual relationship for SW precipitation

  13. DJF- and MAM- SSTs/Winds and JJA0 SW Precip Obs CFS DJF- MAM- JJA0

  14. Same problem with the NAME Tier-1 precipitation Two peaks in CFS

  15. Obs CFS Same problem with the NAME Tier-1 precipitation

  16. SW NAME Tier-1 Consistency between CPC reconstructed & unified data

  17. Summary • CFS T126 simulates the means and seasonality of U.S. regional precipitation better than does CFS T62 • The worst CFS simulation occurs to the SW precipitation • The CFS generates (completely) unrealistic amplitude and phase of the annual cycle of the SW precipitation • The CFS overestimates the interannaul variability of the SW precipitation and its link to the Pacific SST and winds, but underestimates the precipitation’s connection to the Atlantic SST and atmospheric circulation

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