An Objective Identification Technique for Regional Extreme Events

An extreme weather and climate event does not only mean that an extreme occurs at an individual point (station), but more generally it has a certain impacted area and duration, which means that it is a regional extreme event (REE). How to identify a REE is the basis for studies in this area. An objective identification technique for REE (OITREE), which is based on the model of "the string of candied fruits." is proposed in this study. This technique consists of five steps: to select a daily index for individual points (stations), to partition natural daily abnormality belts. to distinguish the event's temporal continuity, to establish an index system for regional events, and to judge extremity for regional events. In the index system developed specially for regional events, there are five single indices, namely extreme intensity, accumulated intensity, accumulated area. maximum impacted area and duration, as well as an integrated index and the spatial location. In this study, the proposed method was first applied to examine four types of REEs in China: heavy precipitation, drought. high temperature. and low temperature. Results show that the technique is skillful in identifying REEs, demonstrating the usefulness of the proposed method in detecting and studying of REEs and operational application.