HR: 15:10h
AN: H23K-07    [Abstracts]
TI: NEXRAD Reflectivity Derived Rainfall Estimates Comparison With Measurement from Co- located Rain Gauges Newfel Mazari, Hongjie Xie, Hatim Sharif, Jon Zetler
AU: * mazari, n
EM: newfel@yahoo.com
AF: University Of Texas at San Antonio, Earth and Environmental Science, San Antonio, TX 78249, United States
AU: hongjie, x
EM: hogjie.xie@utsa.edu
AF: University Of Texas at San Antonio, Earth and Environmental Science, San Antonio, TX 78249, United States
AU: Sharif, H
AF: utsa san Antonio, eNVIRONMENTAL ENGINEERING, San Antonio, 78249, United States
AU: Zietler, J
AF: nATIONAL WEATHER SERVICE, nEW BRAUFELS TEXAS, NEW BRAUFELS, TX 78249, United States
AB: Rain gauges were the main means to measure rainfall until the introduction of radar technology in hydrology and meteorological studies. Radar can cover areas inaccessible with conventional rain gauges networks. The application of NEXRAD products in the estimation of quantity and spatial distribution of precipitation has recently improved with the offering of Multi-sensor Precipitation Estimator (MPE) products. However the accuracy of radar precipitation estimates remains mostly unclear. We used a set of two tipping bucket rain gauges for comparison with radar rainfall estimates derived from level II reflectivity. A power law Z = 300 R1.4 was used in this study. We used non-zero rainfall events pairs (radar, gauge), with a threshold of 0.31 mm corresponding to a reflectivity of 15 dBZ. The results indicated that the best time delay between radar reflectivity measurement and the rain gauges measurement of rainfall results was 7 minutes. The time delay is due to the fact that the radar observes rainfall aloft (in our case around 1,200 meters), while the rain gage records rainfall only at ground level. Data were collected from September 2006 to March 2007. Statistical analysis resulted in an R-square of 0.85 for one rain gauge and 0.80 for the other, with a P-value of 0.0001. Furthermore, the radar underestimated rain rates by 23 % and overestimated rain rate by 11% for rain gauge one and two, respectively. Our analysis indicates that the difference between the rain gauges is mostly due to hardware inconsistencies.
DE: 1800 HYDROLOGY
DE: 1840 Hydrometeorology
SC: Hydrology [H]
MN: 2007 Fall Meeting