1. Quality Control of the ATLAS II Precipitation Gauge Data Jeremy Lehmann Beth Tfiloh High School, Grade 12 Mentor: Dr. George Huffman Mesoscale Atmospheric Processes Branch: Code 613.1

2. Acknowledgements Dr. George Huffman Dr. Yolande Serra Dr. Tom Bell Dr. Robert Adler

3. Global Rainfall A variety of satellites estimate precipitation across the world Validation from the ground is essential to verify accuracy of satellites TRMM PR (red) TRMM TMI (cyan) SSM/I (3 sat.; yellow) AMSR-E (blue) AMSU-B (3 sat.; green) IR (black) Adapted from Huffman, et al. 2006.

4. TRMM Combination Rainfall Loop Accessible at http://trmm.gsfc.nasa.gov TRMM Combination Global Rainfall Estimates: Aug. 3, 2006 - Aug. 10, 2006

5. TAO/TRITON Array Array of 70 moored buoys across the Pacific Ocean, 8 o N to 8 o S, 137 o E to 95 o W Operated by PMEL Contain a multitude of instruments that measure wind speed, air temperature, and sea surface temperature 27 buoys contain rain gauges Available from PMEL Website: http://www.pmel.noaa.gov/tao/

6. ATLAS II Self-Siphoning Rain Gauges Mounted 3.5 m. above ocean surface Rainfall rates are compiled after each deployment Rainfall accumulations recorded every min., differenced over 10 min. Dr. Ken Bowman combined these rainfall rates into 3 hr. periods Available from PMEL Website: http://www.pmel.noaa.gov/tao/

7. Instrument Noise Rain gauges have inherent noise Creates negative as well as false positive values Objectives Characterize Noise Determine the threshold needed to eliminate noise from buoys

8. Noise Episodic and not constant Varies within each buoy and within each deployment Oscillates across zero during dry periods Contain anomalous periods

9. Rainfall Distribution Histogram Distribution clusters around zero Peak of rainfall rate distribution, however, is negative –Attributed to evaporation –On the order of -.001 to -.008 mm/h –Value is on order of previously calculated monthly evaporation rate

10. Time Dependent Threshold Determined by calculating 10 th percentile of negative values, incorporating evaporation value, and reflecting across origin No statistical result as threshold varies too much Provided general area of threshold

11. Determining Constant Threshold Noise vs. Light Rain Events How much data can be discarded? IMAGE OF SERIES AND DIFFERENT LINES OF DIFFERENT THRESHOLDS

12. Results Decided.2 mm/h as set threshold for each buoy Anomalous periods defined as periods of data in which noise above the threshold contributed to more than 4% of total data Threshold effectively eliminated the noise

13. Results Cont. Buoy% Data Discarded % of Noise in Data 9n140w3.628.393 5n165e0.517 8s165e.425.359 8n110w0.296 5s165e.955.469 8n165e6.2581.317 5n95w01.041 2s165e0.647 2n165e0.250 5n140w0.141 8n95w3.1772.080 0n165e.4778.036 0n180w3.8201.483 0n170w01.121 Buoy% Data Discarded % of Noise in Data 2n95w2.5471.370 5s95w0.830 5s140w0.995 2n140w01.594 8s95w17.3402.521 0n125w03.597 2s95w1.7524.615 0n95w03.571 2s140w1.0791.300 0n155w2.4266.250 0n140w03.086 0n110w12.62310.714 8n125w*033.333 * Only 3 Months of Data

14. Results Cont. Thresholded rain rate very similar to original rain rate

15. Conclusion Noise in ATLAS II precipitation gauges is greatly varies and generally oscillates across zero Using negative noise values, we chose.2 mm/h as our threshold Threshold –Effectively eliminates noise (generally accounts for less than 3%of data) –Thresholded data closely aligned with original data Anomalous periods were defined and did not constitute large percentage of data Threshold does discard very light rain events

16. Future Applications Provides revised data sets used in validation with satellites Methodology can be used to lower threshold if needed Principles can be applied to future TAO/TRITON buoy data as well as PIRATA buoy data in the Atlantic

17. Intern Experience Fueled my passion for meteorology Learned importance of math and physics as well as presentation and writing skills Through my research, attendance at Earth Science seminars and conversations with other meteorologists, I’ve witnessed the breadth of the field Realized the tremendous opportunity at NASA to perform research in Earth Science and that there is much to be discovered about our planet

18. Acronyms AMSU B: Advanced Microwave Sounding Unit-B AMSR-E: Advanced Microwave Scanning Radiometer for Earth Observing System ATLAS: Autonomous Temperature Line Acquisition System IR: Infrared NASA: National Aeronautics and Space Administration PIRATA: Pilot Research Array in the Tropical Atlantic PMEL: Pacific Marine Environmental Laboratory PR: Precipitation Radar SSM/I: Special Sensor Microwave Imager TAO/TRITION: Tropical Atmosphere Ocean / Triangle Trans- Ocean Buoy Network TMI: TRMM Microwave Imager TRMM: Tropical Rainfall Measuring Mission

19. References Bowman, K. P., 2004. Comparison of TRMM Precipitation Retrievals with Rain Gauge Data from Ocean Buoys. J. Climate., 18, 178-190. Huffman, G. J., R. F. Adler., D. T. Bolvin, G. Gu, E. Nelkin, K. P. Bowman, Y. Hong, E. F. Stocker, and D. B. Wolff, 2006. The TRMM Multi-satellite Precipitation Analysis (TMPA): Quasi-Global, Multi-Year, Combined Sensor Precipitation Estimates at Fine Scales. To appear in J. Hydrometeorology. McPhaden, M. J., 2006. Tropical Atmosphere Ocean Project. http://www.pmel.noaa.gov/tao. http://www.pmel.noaa.gov/tao Pierce, H., 2006. TRMM: Tropical Rainfall Measuring Mission. http://trmm.gsfc.nasa.gov. http://trmm.gsfc.nasa.gov Serra, Y. L. and M. J. McPhaden, 2002. Multiple Time and Space Scale Comparisons of ATLAS Buoy Rain Gauge Measurements to TRMM Satellite Precipitation Measurements. Submitted to J. Appl. Meteor. Serra, Y. L., P. A’Hearn, H. P. Freitag, and M. J. McPhaden, 2001. ATLAS Self- Siphoning Rain Gauge Error Estimates. J. Atmos. Iceanic Technol., 18, 1989-2002.