1 / 20

Comparison of PPS and QPE Rainfall Estimates for Summer 2013 Heavy Precipitation Events

Comparison of PPS and QPE Rainfall Estimates for Summer 2013 Heavy Precipitation Events. Mitchell Gaines National Weather Service Mount Holly, NJ. Purpose .

esme
Download Presentation

Comparison of PPS and QPE Rainfall Estimates for Summer 2013 Heavy Precipitation Events

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Comparison of PPS and QPE Rainfall Estimates for Summer 2013 Heavy Precipitation Events Mitchell Gaines National Weather Service Mount Holly, NJ

  2. Purpose • To evaluate the PPS and QPE Algorithms and processes of rainfall estimation with relation to ground truth precipitation measurements for several heavy rainfall events from this past Summer over the Philadelphia region. Photo: Pennsville, NJ Jul 28,2013 Source: NJ.com

  3. Rainfall Records Broken • Wettest June and July on record at Philadelphia International Airport. • 8.03 inches in about six hours (daily rainfall record) at Philadelphia on July 28th • Wettest June on record in Wilmington, DE, and Atlantic City, NJ

  4. Legacy PPS vs. Dual-Pol QPE • PPS • From base reflectivity (Z)  Digital Hybrid Scan • Single Z-R relation used at any time (choice of coefficients) • Gage bias adjustment available • Suffers from bright band, hail contamination, beam blockage • QPE • From Z, ZDR, CC, KDP, MLDA, HCA  Digital Precip Rate • Three relations: R(Z), R(Z,ZDR), R(KDP) plus adjustments for frozen hydro-meteors • No gage bias adjustment • Dual-pol input should mitigate many PPS limitations

  5. WFO Mount Holly, NJ County Warning Area

  6. KDIX/KDOX Coverage to 150 km KDIX KDOX

  7. Methodology • Identify heavy rainfall events over the Philadelphia region this summer which led to flash flooding. • (6/3/13, 6/7/13, 6/10/13, 6/18/13, 7/1/13, 7/13/13, 7/23/13, 7/28/13) • Use Multi-Radar Multi-Sensor System (MMRS) http://nmq.ou.edu/legacy2012.html • Compare rain gauge data to radar estimates from both the PPS and QPE for that particular point. • Exclude data less than 20km or more than 150 km from the radar. • Excluded zero or trace values, gauge or radar.

  8. Methodology (Cont’d) • Use of DIX and DOX WSR 88D radars to apply estimation methods. • Variables measured to determine preference • RMSE, Correlation Coefficient, Mean Bias • Graphical scatter plots • Focus on July 28th event ( 03z to 03z timeframe with scatterplots)

  9. July 28th Heavy Rainfall • Localized heavy rainfall event • 8.03 inches of rain in about six hours at Philadelphia International, less than one inch at Northeast Philadelphia. Dual-pol (QPE) rainfall estimate image

  10. Synoptic Overview, July 28

  11. PPS DIX Radar 7/28

  12. QPE DIX Radar 7/28

  13. PPS DOX 7/28

  14. QPE DOX 7/28

  15. Overall Results

  16. Overall Results

  17. Average Results

  18. Conclusions • Lower mean bias with QPE • Similar CC values • Lower RMSE values with QPE, all but 7/23. • - DOX results featured higher Dual-Pol totals while Legacy was a better fit in several cases.

  19. Conclusions • QPE is preferred for rainfall amounts over 2 inches in heavy rainfall events. • Much better at “capturing” higher amounts of QPF. • Seen in “curve” throughout many of the scatterplots • Use of melting layer more of a role in cold season • Zimmerman Presentation (NWS, Wakefield)

  20. Questions • Special thanks to the • -NROW Conference Steering Committee • -The University of Albany • National Weather Service Mount Holly, NJ • SOO Al Cope

More Related