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Analysis of Extreme Precipitation Events Using Master Self-Organizing Maps in North America (1989-2007)

This study utilizes Master Self-Organizing Maps (SOM) to analyze widespread extreme precipitation events during the December-January-February (DJF) months from 1989 to 2007 in North America. By employing ERA-Interim data and WRF model simulations, the analysis focuses on the 99th percentile of precipitation events identified across at least 25 grid points. It highlights node selection challenges, particularly in regions where circulation patterns do not indicate favorable conditions for extreme precipitation. The results emphasize the importance of refined SOMs to improve event detection and circulation feature mapping.

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Analysis of Extreme Precipitation Events Using Master Self-Organizing Maps in North America (1989-2007)

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  1. SOMs Work Analysis Region Top Widespread Events Location of Extreme Precipitation

  2. DJF Master SOM • Produced with ERA-Interim + SN WRF-50.hPa MSLP anomalies (1989-2007) • Widespread extreme days (99th percentile, w/ at least 25 grid points) from WRF mapped onto Master SOM

  3. 99th Percentile

  4. Top 10 DJF Composite

  5. Top 5 DJF Composite

  6. Top DJF Event

  7. Extreme Node Selection • In some analysis regions, nodes are being accessed that don’t show favorable circulation for widespread precip. extremes • Some regions may need a smaller Master SOM, as strong features far from region may confound node selection

  8. Native WRF output vs. NCDC-based WRF output

  9. Comparing Node Frequencies • Extracted WRF widespread extreme events from N. American analysis region • Extracted NCDC station extremes from same regions • Extracted WRF output from grid points closest to NCDC station • Compared node frequencies from the three sources

  10. Native WRF: L-H-L signal seems to be the dominant circulation feature. Highly accessed nodes on the periphery of SOM space, in general.

  11. NCDC observations don't really show the L-H-L pattern that we find in the model output; we find a strong Aleutian low and a region of relaxed high pressure over the eastern part of domain.

  12. Similar L-H-L as found in native WRF. Highest frequency node, however, shows a low pressure feature over Gulf of Alaska, with H pressure over the Bering Strait.

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