McGill Algorithm for Precipitation nowcasting by Lagrangian Extrapolation (MAPLE) applied to the South Korean Radar Netwotk. Part 2: Real-time verification for the summer season

The MAPLE system has been implemented in real-time in Korea since June 2008, producing forecasts up to 6 hours every 10 minutes. An object-oriented verification method has been applied for the summer season (June-July-August) over the Korean Peninsula to evaluate and understand the characteristics of the forecast results. The CRA (contiguous rain area) approach is used to decompose the total error into the different error components; location, pattern, and volume errors.

The mean displacement error is smaller than 20 km up to the 3-h forecasts and increases with forecast time. The ratio between the displacement (location) error and the total error is less than 7 % even for a 3-h forecast. This result indicates that MAPLE produces reliable forecast in terms of precipitation location. However, the pattern error is larger than 90% of the total error.

Contingency scores that are defined with different categories of rain intensity and displacement errors show the outstanding performance up to 2.5 hours. MAPLE overpredicts rain areas with the threshold of 1 mm/h rain intensity throughout forecast periods. However, the heavy rainfall events are poorly predicted due to the inherent limitation of extrapolation-based nowcasting technique.