A Study on the Blue Rainstorm Warning Index Based on Characteristics of Short-Period Heavy Rainfall in Beijing

Based on minute rainfall data collected at 362 automatic weather stations from June to September between 2013 and 2015 in Beijing, the authors analyze the characteristics of short-period heavy rainfall in summer, and propose a blue rainstorm warning (BRW) index. The analysis suggests that:1) The maximum rainfall intensities in 5 minutes and 10 minutes in BRW events (events that meet the BRW criterion) are about five times that in other events, and the rainfall intensity decreases significantly after reaching the BRW criterion. 2) 63.0% of the total BRW events that meet the criterion last no more than 60 min after the rain begins, and the BRW events that start during 1800 LST to 0100 LST count for 60% of the total BRW events. 3) High minute-rainfall intensity can be a good index for BRW. If a BRW is issued when 5-minute rainfall reaches 7.7 mm, the lead time will be 16.7 min and the HSS score can be up to 0.503.