1. Rainfall Distribution within an Hydro-Estimator Pixel Ian Garcia 1, E. W. Harmsen 2 and Jorge Canals Garcia 3 1. Undergraduate Research Assistant, Dept. of Biology 2. Associate Professor, Dept. of Ag. and Biosystems Eng. 3. Graduate Research Assistant, Dept. of Computer Engineering, University of Puerto Rico – Mayagüez Campus

2. Acknowledgements We would like to thank the following students for their help on this project: Marcel Giovanni Prieto, Victor Hugo Ramirez, Yaritza Perez, Romara Santiago, Alejandra Roja, Julian Harmsen and Lua Harmsen. Dr. Luis Perez and Dr. Nazario Ramirez for use of their GPS equipment. We also want to thank NOAA CREST for their financial support of this project. Additional support was received from NASA EPSCoR, USDA-TSTAR and NSF-CASA projects. This work made use of Engineering Research Centers Shared Facilities supported by the National Science Foundation under NSF Cooperative Agreement No. EEC-0313747. Any Opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation.

3. Problem The QPE validation study of Cruz Gonzalez (2006) raised a concern relative to the validation methodology itself; specifically, is it appropriate to compare a single rain gauge value of rainfall with estimates from the HE algorithm, which covers an area of 16 km 2 ? Other potential sources of error include: rain gauge inaccuracy, and assumptions made in the development of the HE algorithm that may be violated under tropical rainfall conditions. Definitions: QPE = quantitative precipitation Estimation HE = Hydro-Estimator

4. Long-term Objectives Validate and enhance QPE methods in Puerto (HE, SCaMPR, GMSRA) Understand pixel-scale rainfall vaiability Develop a satellite QPE flash flood Nowcast for a testbed in western PR.

5. Short-term Objectives Install 16 digital rain gauges within a HE pixel Collect data from the rain gauges for at least a one year period Evaluate rainfall statistics Compare rain gauge data with HE-estimated data

6. Methodology 1. The center points of the HE pixels were obtained from NOAA-NESDIS. 2. An appropriate HE pixel was selected, which included a relatively large range of topographic relief east of the Mayagüez Bay in western Puerto Rico. 3. Using ArcGIS, sixteen points were located (evenly spaced) within the HE pixel. These sixteen areas will be referred to as sub-areas. 4. With the assistance of a ground positioning system (GPS), students located properties which were as close as possible to the center point locations identified in step no. 3. In each case it was necessary to obtain permission from the property owner before installing the rain gauges. 5. The actual coordinates of the installed rain gauges were recorded and entered into ArcGIS.

7. Mayaguez Bay Miradero Study Area

8. Final rain gauge locations

9. Results RESULTS

10. Pixel Rainfall Statistics

11. Gauges with Zero Rain Instrument is at 200 cm Height

13. Rainfall Variation with Time August 6 th, 2006

14. Comparison of rain gauges with the Hydro Estimator (HE) NESDIS provide us with HE data for Aug 1 st through Aug 8 th, 2006. A comparison was made with the Aug 6 th rain gauge data The HE did not register any rain on Aug 6 th, whereas the rain gauges recorded an average depth of 30.8 mm.

15. Conclusions Nine storms were evaluated between Aug and Oct, 2006. Measured rainfall within an HE pixel (4 km x 4 km) can be highly variable. The HE did not register any rain in the pixel as compared to 30.8 mm measured by the rain gauges.

16. Future Work Continue collecting and analyzing rain gauge data. Obtain additional HE data from NESDIS to compare with the rain gauge data. Obtain SCaMPR and GMSRA data for comparison with the rain gauge.

17. Questions?