Assessing ERA5 Representations of Near-Surface Air Temperature for Pavement Design in Canada

Accurate climate inputs are essential for predicting pavement performance using Pavement Mechanistic-Empirical Design (PMED). This study evaluates the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis Version 5 (ERA5) as an alternative to the Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) for flexible pavement design in Canada. Hourly air temperature data from both products were compared with weather station observations across multiple cities, and their effects on pavement distress indicators, including IRI, total rutting, asphalt concrete (AC) rutting, and bottom-up fatigue cracking, were analyzed. Sensitivity analyses examined traffic, asphalt thickness, and subgrade stiffness. ERA5 effectively captured long-term temperature trends and performed well in Atlantic cities, while MERRA-2 aligned more closely in inland and western regions. Rutting predictions were most affected, with differences reaching 12% for AC rutting and 3% for total rutting. Overall, ERA5 is a statistically comparable alternative climate input for PMED applications in Canada, supporting improved pavement performance assessment in regions with limited observational data.