Marine Heat Waves and Cold Spells – Multiple Analysis / Definitions (MHW-MAD): A Multi-Definition Global Marine Heatwave Database from Satellite Sea Surface Temperature Data

MHW-MAD is a multi-definition global marine heatwave (MHW) and marine cold spell (MCS) database derived from ESA SST-CCI satellite sea surface temperature. It applies the Hobday et al. (2016) event-detection framework repeatedly under systematically varied methodological choices, allowing users to assess how sensitive marine heatwave statistics are to definitional decisions that are usually made once and left implicit. Datasets vary across five axes: detrending (raw SST as observed, or linear trend removed); climatology baseline (WMO standard normal 1991–2020, a reanalysis-derived baseline, or fixed 30-year windows stepping forward one year at a time from 1982–2011 to 1995–2024); percentile threshold (90th, 95th, 99th); minimum event duration (5, 10, or 30 days); and output type (event categories, SST anomalies, or the underlying climatology and threshold fields). All products are on a 0.05° global grid (7200 × 3600), daily from 1982-01-01 to 2024-12-31, in CF-compliant NetCDF-4. This Zenodo record is the citable landing point for MHW-MAD and contains full documentation and a machine-readable manifest of every dataset in the product. The gridded fields themselves are on the order of terabytes, well beyond the capacity of this repository, and are distributed openly by the Danish Meteorological Institute from two endpoints requiring no registration: bulk NetCDF download at https://download.dmi.dk/public/MHW/, and subsetting, OPeNDAP and WMS services at https://erddap.dmi.dk/erddap/. Both serve identical files. Please cite this record when using MHW-MAD, regardless of access route.