Aviation Turbulence Forecasting at Upper Levels with Machine Learning Techniques based on Regression Trees

Abstract

We explore the use of machine learning (ML) techniques, namely regression trees (RT), for the purpose of aviation turbulence forecasting at upper levels (20 – 45 kft altitude). In particular, we develop a series of RT-based algorithms that include random forests (RF) and gradient boosted regression trees (GBRT) methods. Numerical weather prediction model prognostic variables and derived turbulence diagnostics based on 6-h forecasts from the 3-km High-Resolution Rapid Refresh (HRRR) model are used as features to train these data-driven models. Training and evaluation are based on turbulence estimates of eddy dissipation rate (EDR) obtained from automated in-situ aircraft reports. Our baseline RF model, consisting of 100 trees with 30 layers of maximum depth, significantly reduces forecast errors for EDR < 0.1 m2/3 s−1 (which corresponds roughly to null and light turbulence) when compared to a simple regression model, increasing the probability of detection and in turn reducing the number of false alarms. Model complexity reduction via GBRT and feature relevance analyses is performed, indicating that considerable execution speed ups can be achieved while maintaining the model’s predictive skill. Overall, the ML models exhibit enhanced performance in discriminating the EDR forecast among the light, moderate and severe turbulence categories. In addition, these artificial intelligence techniques significantly simplify the generation of new NWP and grid-spacing specific turbulence forecast products.