Two Different Integration Methods for Weather Radar-Based Quantitative Precipitation Estimation

We discuss two different integration methods for radar-based quantitative precipitation estimation (QPE): the echo intensity integral and the rain intensity integral. Theoretical analyses and simulations were used to test differences between these two methods. Cumulative rainfall calculated by the echo intensity integral is usually greater than that from rain intensity integral. The difference of calculated precipitation using these two methods is generally smaller for stable precipitation systems and larger for unstable precipitation systems. If the echo intensity signal is sinusoidal, the discrepancy between the two methods is most significant. For stratiform and convective precipitation, the normalized error ranges from -0.138 to -0.15 and from -0.11 to -0.122, respectively. If the echo intensity signal is linear, the normalized error ranges from 0 to -0.13 and from 0 to -0.11, respectively. If the echo intensity signal is exponential, the normalized error ranges from 0 to -0.35 and from 0 to -0.30, respectively. When both the integration scheme and real radar data were used to estimate cumulative precipitation for one day, their spatial distributions were similar.