Zhou et al. (2026) Future exposure to dry and moist heat extremes linked to soil moisture regulation

Identification

• Journal: Journal of Hydrology
• Year: 2026
• Date: 2026-10-26
• Authors: Jingwei Zhou, Dragan D. Milošević, Adriaan J. Teuling
• DOI: 10.1016/j.jhydrol.2026.136681

Research Groups

• Hydrology and Environmental Hydraulics Group, Wageningen University & Research, Wageningen, Netherlands
• Meteorology and Air Quality Group, Wageningen University & Research, Wageningen, Netherlands

Short Summary

This study quantifies how land-atmosphere interactions, particularly soil moisture dynamics, modulate the intensification and population exposure patterns of future dry and moist heatwaves globally, finding unprecedented increases in both types of heatwaves across mid-latitude regions, often exceeding Paris Agreement thresholds.

Objective

• To systematically quantify and compare how soil moisture dynamics modulate the intensification and consequent population exposure patterns of future dry and moist heatwaves globally, using multi-model climate simulations.

Study Configuration

• Spatial Scale: Global, with regional analyses for 10 IPCC AR6 climate reference regions. Climate data interpolated to a uniform 2.5° longitude by 1.875° latitude grid. Population data (1/8° × 1/8°) aggregated to the climate grid.
• Temporal Scale:
  • Pre-industrial: 1850–1900
  • Historical: 1850–2014
  • Present/Baseline: 1980–2010 (for heatwave threshold calculation), 2000–2020 (for model validation), 2000–2030 (for population exposure change baseline)
  • Future: 2040–2070 (main future period), under Shared Socioeconomic Pathway (SSP) 585. Population data spans 2000–2070 at decadal intervals.

Methodology and Data

• Models used:
  • Coupled Model Intercomparison Project Phase 6 (CMIP6) models (three selected for robust land-atmosphere feedback simulation and data availability).
  • CMIP6 experiments: historical, Shared Socioeconomic Pathway (SSP) 585 (ScenarioMIP), and Land Feedback Model Intercomparison Project with prescribed Land Conditions (LFMIP-pdLC) of LS3MIP.
  • Multi-model ensemble mean computed to reduce individual model biases.
• Data sources:
  • Climate model data from CMIP6: near-surface air temperature (T), near-surface relative humidity, surface latent heat flux, and total soil moisture.
  • Gridded global population data (1/8° × 1/8°) aligned with SSP585 (Jones and O'Neill, 2020; Jones and O’Neill, 2016).
  • ERA5-Land global reanalysis product (Muñoz-Sabater et al., 2021) for independent model validation: near-surface air temperature (T) and near-surface dewpoint temperature (Td).
  • Heatwave identification: Daily mean near-surface air temperature (for dry heatwaves) or wet-bulb temperature (for moist heatwaves) exceeding the 90th percentile threshold of the 1980–2010 baseline for three or more consecutive days. A 11-day sliding window was used for threshold calculation.
  • Wet-bulb temperature (WBT) calculation: WBT = T * arctan(0.151977 * ((rh+8.313659)^(1/2))) + arctan(T+rh) - arctan(rh-1.676331) + 0.00391838 * (rh^(3/2)) * arctan(0.023101*rh) - 4.686035.
  • Soil moisture impacts: Quantified as the difference between control (CTL) simulations (dynamic soil moisture) and LFMIP-pdLC experiments (fixed soil moisture to 1980–2014 climatology).
  • Statistical significance: Evaluated using the Kolmogorov-Smirnov (KS) test.
  • Population exposure: Defined as the percentage of population exposed to dry heatwaves with yearly magnitudes greater than 303.15 K or moist heatwaves with yearly magnitudes greater than 298.15 K.

Main Results

• Unprecedented increases in both dry and moist heatwave magnitudes are projected across mid-latitude regions, with many areas already surpassing the 2 K Paris Agreement threshold and some exceeding 6 K relative to pre-industrial conditions.
• Dry heatwaves consistently exhibit greater intensification and trends than moist heatwaves globally.
• Soil moisture dynamics generally induce more pronounced changes in dry heatwaves compared to moist heatwaves.
• Northern parts of South America, the Arabian Peninsula, and South Asia are identified as hotspots for more severe dry and moist heatwaves in the future period (2040–2070).
• Most regions are experiencing increasing population exposure to heatwaves, with African regions showing a 30% increase in population exposure to severe moist heatwaves.
• Soil moisture amplifies population exposure to heatwaves in most places, except for the Arabian Peninsula where it shows mediating (reducing) effects.
• Western and Central Europe (WCE), the Mediterranean region (MED), and western North America (WNA) show markedly higher projected increases of both heatwaves.
• Since 2015–2025, all domains except the Amazon region (AMZ) have experienced dry heatwave intensification exceeding 2 K relative to pre-industrial levels, while AMZ is projected to cross 1.5 K for moist heatwave magnitude increases during 2025–2035.

Contributions

• Provides the first systematic, mechanism-oriented comparative framework to analyze how soil moisture dynamics differently modulate future dry and moist heatwave magnitudes using CMIP6 LS3MIP experiments.
• Quantifies and compares projected changes in the magnitude of both heatwave types and associated population exposure from pre-industrial to future periods.
• Highlights the necessity of incorporating region-specific land-atmosphere feedbacks, which modulate dry versus moist heatwave intensification differently, for accurate risk quantification and targeted adaptation strategies.
• Utilizes a "maxima season" approach to capture peak heatwave hazard across diverse regions, moving beyond conventional static summer season analyses.

Funding

• J. Zhou is supported by the China Scholarship Council.
• Acknowledgments are extended to the World Climate Research Programme, CMIP6, climate modeling teams, Earth System Grid Federation, NASA's Socioeconomic Data and Applications Center (SEDAC), and Copernicus Climate Change Service for ERA5-Land data.

Citation

@article{Zhou2026Future,
  author = {Zhou, Jingwei and Milošević, Dragan D. and Teuling, Adriaan J.},
  title = {Future exposure to dry and moist heat extremes linked to soil moisture regulation},
  journal = {Journal of Hydrology},
  year = {2026},
  doi = {10.1016/j.jhydrol.2026.136681},
  url = {https://doi.org/10.1016/j.jhydrol.2026.136681}
}