A Machine Learning Framework for Predicting and Understanding the Canadian Drought Monitor

Drought is a costly natural disaster that impacts economies and ecosystems worldwide, so monitoring drought and communicating its impacts to individuals, communities, industry, and governments is important for mitigation, adaptation, and decision-making. This research describes a novel machine learning framework to predict and understand the Canadian Drought Monitor (CDM). This fully automated approach is trained on nearly two decades of expert analysis and would assist the comprehensive monitoring of drought impacts without the continued requirement of ground support, a benefit in many data-limited areas across the country. The framework also integrates the Shapley Additive Explanation (SHAP) variable importance metric to provide insight into drought dynamics in near real-time, demonstrating its usefulness for understanding the value of different data sets for drought assessments and dispelling the commonly held misconception that machine learning models are not useful for inference. The results demonstrate that the model can effectively predict the CDM maps and realistically capture the evolution of drought events over time. A SHAP analysis found that the Prairie drought of 2015 was related to a strong El Nino event that reduced water supply to a region already facing long-term water deficits, and the subsequent reduction in groundwater availability was detected by the Gravity Recovery and Climate Experiment satellite. Overall, this research shows strong potential to streamline the CDM methodology, integrate scientific insight into operations in near real-time using SHAP values, and provide an avenue to retrospectively extend the CDM for evaluating current and future drought events in a historical context.