Challenges and Opportunities Using Impact Data for Impact-based Forecast Verification.

The collection and management of data describing socio-economic impacts resulting from hydrometeorological hazards is critically important. Such Impact Data may be used to contextualize upcoming hazardous events, provide situational awareness, and track the efficacy of mitigating actions. Importantly, Impact Data can provide the observations of impacts necessary to evaluate the performance of Impact-based Forecasts and Warnings (IbFW).  There are many sources of publicly accessible impact data available including international organizations, governments, academic institutions, and news websites. Differences in the purpose, methodologies, format, and quality of collection across agencies has led to a fragmented and inconsistent picture of impacts to date, limiting their utility.

To understand the implications of using freely available impact data for the purpose of IbFW evaluation, seven freely available sources of impact data were assessed, and six types of bias interrogated (geographic, hazard, temporal, threshold, accounting, and systemic biases). 'Our analysis shows that different types of bias are present across the data sources investigated The biases affect the coverage, severity, timing, geographic scale, and accuracy of impact observations which influence their utility in IbFW evaluation. Despite these challenges, our assessment suggests that using a range of data sources together can provide a more holistic observation of the impacts of hydrometeorological events. Here we present results of the interrogation of Impact Data for IbFW evaluation, and the processing steps required to harmonize Impact Data across multiple sources for utilization within an evaluation workflow. Initial results of a routine objective IbFW evaluation approach are also presented, and opportunities and challenges of using Impact Data for IbFW evaluation highlighted.