Knowledge-Guided Machine Learning: Illustrating the use of Explainable Boosting Machines to Identify Overshooting Tops in Satellite Imagery

Machine learning (ML) algorithms have emerged in many meteorological applications. However, these algorithms struggle to extrapolate beyond the data they were trained on, i.e., they may adopt faulty strategies that lead to catastrophic failures. These failures are difficult to predict due to the opaque nature of ML algorithms. In high-stakes applications, such as severe weather forecasting, it is crucial to avoid such failures. One approach to address this issue is to develop more interpretable ML algorithms. The primary goal of this work is to illustrate the use of a specific interpretable ML algorithm that has not yet found much use in meteorology, explainable boosting machines (EBMs). We demonstrate that EBMs are particularly suitable to implement human-guided strategies in an ML algorithm. As a guiding example, we show how to develop an EBM to detect overshooting tops (OTs) in satellite imagery. EBMs require input features to be scalar. We use techniques from knowledge-guided machine learning to first extract scalar features from meteorological imagery. For the application of identifying OTs, this includes extracting cloud texture from satellite imagery using gray-level co-occurrence matrices. Once trained, the EBM was examined and minimally altered to more closely match strategies used by domain scientists to identify OTs. The result of our efforts is a fully interpretable ML algorithm developed in a human–machine collaboration that uses human-guided strategies. While the final model does not reach the accuracy of more complex approaches, it performs reasonably well, and we hope it paves the way for building more interpretable ML algorithms for this and other meteorological applications. The purpose of this work is to introduce the interpretable machine learning method of explainable boosting machines (EBMs) to an atmospheric science audience by closely examining how they can be used to detect the location of overshooting cloud tops, which have been associated with the occurrence of severe weather, in satellite imagery. Interpretable machine learning methods are important in high-risk situations such as overshooting top detection as they allow forecasters to have a better understanding of how exactly an identification is made. We walk through how to build, interpret, and modify the machine learning algorithm for use on this task and discuss other applications that could benefit from this approach.