The evaluation of drop size distrubutions captured by two weather radars in mid Missouri

Abstract

In 2015, an X-band dual-polarization Doppler radar (MZZU) was installed in Columbia, Missouri. Its goal is to fill a gap in radar coverage and provide a precipitation climatology for Mid-Missouri. MZZU captures precipitation data by transmitting frequencies at 9.35 GHz. During heavy rainfall events, however, the power of the emitted X-band waves is attenuated. Currently, an attenuation correction algorithm is processing MZZU data to improve the accuracy of the radar. This study uses a K-band vertical pointed microwave rain radar (MRR) to evaluate the need to further calibrate MZZU data. Eight events were analyzed and the correlation of attenuated corrected reflectivity from MZZU and reflectivity from the MRR were calculated. The correlation of reflectivity values was 0.77 with a RMSE of 4.73 dBZ in all elevations. MZZU underestimated reflectivity values with an average negative bias of 7.71 dBZ. A linear regression line was fitted as well with slope values ranging from 0.61-0.71. Specifically in events with moderate rainfall, the correlation improved with R2 values greater than 0.9; however, the bias increased to 11.68 dBZ. This suggests that radome attenuation may be resulting in higher biases in moderate rain events. In all events and elevations, MZZU underestimated reflectivity compared to the MRR. However, the values obtained from the linear relationship between MZZU and the MRR may be used in future studies to calibrate MZZU reflectivity values.