Analysis of the Value Chain in the ‘7.20’ZhengZhou extreme rainfall event

On 20^th July 2021, an extreme rainfall event occurred at Zhengzhou city in China with maximum hourly rainfall of 201.9 mm and 24h accumulated rainfall of 624.1 mm at Zhengzhou weather station. This storm rainfall event caused huge damages of about 40.9 billion Yuan (RMB) property loss and 380 death. Using the Value Chain concept, the functions of observation, weather forecast, hazard forecast, impact forecast, warning and decision during this event were analyzed. The gaps between the “islands” in the Value Chain were emphasized. There are some limits in the observation system to monitor the event and few observations were passed into the next step of weather forecast. The gap between observation and weather forecast was obvious. The skills of global and regional numerical model forecasts were verified. The forecast skills for the extreme rainfall is low, and it is a challenge to forecast the location and amount of the extreme rainfall for the numerical model. How to improve the forecast skills from minutes to days for these extreme weather systems is still a big problem. The ability of hazard and impact forecast were low, and then lead to some delayed or mis decisions. It is indicated that cooperation between mult-discipline is required to improve the ability of hazard and impact forecast. Some high-level hazard warnings were issued during the event. It is helpful for the public and government making decisions and avoiding the damage, but it needs to be improved in some respect. This case is an example to demonstrate the importance of the idea of value chain in hazard mitigation.