Deep Learning With Noisy Labels for Spatiotemporal Drought Detection

Droughts pose significant challenges for accurate monitoring due to their complex spatiotemporal characteristics. Data-driven machine learning (ML) models have shown promise in detecting extreme events when enough well-annotated data is available. However, droughts do not have a unique and precise definition, which leads to noise in human-annotated events and presents an imperfect learning scenario for deep learning models. This article introduces a 3-D convolutional neural network (CNN) designed to address the complex task of drought detection, considering spatiotemporal dependencies and learning with noisy and inaccurate labels. Motivated by the shortcomings of traditional drought indices, we leverage supervised learning with labeled events from multiple sources, capturing the shared conceptual space among diverse definitions of drought. In addition, we employ several strategies to mitigate the negative effect of noisy labels (NLs) during training, including a novel label correction (LC) method that relies on model outputs, enhancing the robustness and performance of the detection model. Our model significantly outperforms state-of-the-art drought indices when detecting events in Europe between 2003 and 2015, achieving an AUROC of 72.28%, an AUPRC of 7.67%, and an ECE of 16.20%. When applying the proposed LC method, these performances improve by +5%, +15%, and +59%, respectively. Both the proposed model and the robust learning methodology aim to advance drought detection by providing a comprehensive solution to label noise and conceptual variability.