Bias-adjusted and downscaled humidex projections for heat preparedness and adaptation in Canada

To help with preparedness efforts of Canadian public health and safety systems for adaptation to climate change, the humidity index (humidex) and three threshold-based humidex indices (annual number of days with humidex greater than 30, 35 and 40) were computed for a multi-model ensemble of climate change projections, over Canada. The ensemble consists of one run from each 19 Coupled Model Intercomparison Project Phase 6 (CMIP6) global climate models and offers historical simulations starting in 1950 and future projections out to 2100 following Shared Socioeconomic Pathways (SSPs): SSP1-2.6, SSP2-4.5 and SSP5-8.5. Each ensemble member was bias-adjusted and statistically downscaled using the Multivariate bias correction—N-dimensional probability density function transform (MBCn) with hourly data from ERA5-Land as the target dataset and following a method proposed by Diaconescu et al. (2023; International Journal of Climatology, 43, 837) to calculate humidex from daily climate model outputs. This paper details the steps for data production including evaluation of the target historical gridded data and selection of downscaling method and presents some of the resulting humidex projections at the end of the century.