Quantitative Precipitation Estimation from a C-Band Dual-Polarized Radar for the 8 July 2013 Flood in Toronto, Canada

Abstract

A heavy rainfall event over a 2-h period on 8 July 2013 caused significant flash flooding in the city of Toronto and produced 126 mm of rain accumulation at a gauge located near the Toronto Pearson International Airport. This paper evaluates the quantitative precipitation estimates from the nearby King City C-band dualpolarized radar (WKR). Horizontal reflectivity Z and differential reflectivity Z DR were corrected for attenuation using a modified ZPHI rain profiling algorithm, and rain rates R were calculated from R(Z) and R(Z, Z DR ) algorithms. Specific differential phase K DP was used to compute rain rates from three R(K DP ) algorithms, one modified to use positive and negative K DP , and an R(K DP , Z DR ) algorithm. Additionally, specific attenuation at horizontal polarization A was used to calculate rates from the R(A) algorithm. Hightemporal-resolution rain gauge data at 44 locations measured the surface rainfall every 5 min and produced total rainfall accumulations over the affected area. The nearby NEXRAD S-band dual-polarized radar at Buffalo, New York, provided rain-rate and storm accumulation estimates from R(Z) and S-band dualpolarimetric algorithm. These two datasets were used as references to evaluate the C-band estimates. Significant radome attenuation at WKR overshadowed the attenuation correction techniques and resulted in poor rainfall estimates from the R(Z) and R(Z, Z DR ) algorithms. Rainfall estimation from the Brandes et al. R(K DP ) and R(A) algorithms were superior to the other methods, and the derived storm total accumulation gave biases of 2.1 and 26.1 mm, respectively, with correlations of 0.94. The C-band estimates from the Brandes et al. R(K DP ) and R(A) algorithms were comparable to the NEXRAD S-band estimates.

10th European Conference on Radar in Meteorology and Hydrology (ERAD 2018) : 1-6 July 2018, Ede-Wageningen, The Netherlands

“…developed an algorithm based on specific horizontal attenuation (A H ) to derive rainfall rates (R(A H )) which is immune to radar mis-calibration and partial beam blockage. In Boodoo et al (2015) several of these algorithms were evaluated for a flooding event that occurred in Toronto in 2013. Very good results were obtained with R(K DP ) and R(A H ) algorithms for that case and these are being considered for use in operational environment rather than the traditional reflectivity rainfall (Z-R) relationship that is currently employed.…”

“…Following the methodology described in Boodoo et al 2015, rainfall retrieval algorithms R(Z H ), R(Z H ,Z DR ), R(K DP ,Z DR ), R(K DP ) and R(A H ), where K DP and A H are specific differential phase and specific attenuation, were applied after pre-processing with standard C-band coefficients. Table 1 lists the algorithms presented in the paper.…”

“…The dual-polarized data are collected at regular 10-minute cycles and Figure 1 shows example raw PPIs of a) Z, b) Z DR , c) ρ HV , d) Ф DP from WKR at 0300Z on June 23 2017. As described in Boodoo et al (2015), separation of precipitating from non-precipitating echoes relies on measurements of ρ HV , signal quality index (SQI) and gradients of Φ DP to determine rainfall regions in the radar scans at 0.5 o elevation. Ground clutter contamination is handled by Doppler filters in the signal processor and applied to the polarimetric measurements in addition to low signal-to-noise correction of ρ HV and Z DR .…”

A Comparison Study of Summer Season Raindrop Size Distribution Between Palau and Taiwan, Two Islands in Western Pacific

“…Raindrop size distribution (RSD) information plays a key role in realizing the rain microphysics (Rosenfeld & Ulbrich, 2003), and in quantitative precipitation estimation (QPE) algorithms (Boodoo et al, 2015;Chapon et al, 2008;Ryzhkov & Zrnic, 1995;Seliga & Bringi, 1976). For instance, modeled RSD parameters are used in rainfall estimation algorithms of National Aeronautics and Space Administration (NASA) Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) (Iguchi et al, 2000;Kozu, Iguchi, et al, 2009;Kozu, Shimomai, et al, 2009) and in Global Precipitation Measurement (GPM) Dual-Precipitation Radar (DPR) (Hou et al, 2008;Liao et al, 2014;Nakamura & Iguchi, 2007).…”

A Statistical Comparison of the Accuracy of Precipitation Estimation Using Dual-Polarization and Single-Polarization Radar

“…Additionally, dual-pol estimates improved the estimate of precipitation when compared to single-pol radar. Boodoo et al (2015) studied the accuracy of C-band dual-polarization estimates for a flood that occurred in July 2013 in Toronto, Canada. The C-band estimates were compared with estimates from the NEXRAD located in Buffalo, New York.…”