Pandey et al. (2026) Dust and smoke layers over the Atlantic Ocean weaken the underlying low-level cloud-top radiative cooling through different pathways

Identification

• Journal: Communications Earth & Environment
• Year: 2026
• Date: 2026-01-16
• Authors: Satyendra K. Pandey, Adeyemi A. Adebiyi
• DOI: 10.1038/s43247-026-03183-x

Research Groups

• Department of Life and Environmental Sciences, University of California - Merced, Merced, CA, USA

Short Summary

This study investigates how elevated dust and smoke layers over the Atlantic Ocean weaken low-level cloud-top radiative cooling. It finds that both aerosol types induce longwave-dominated warming, with dust having a significantly stronger impact on cloud-top cooling and subsequent cloudiness reduction than smoke, through distinct pathways.

Objective

• To investigate the distinct mechanisms by which elevated dust and smoke aerosol layers over the Atlantic Ocean influence underlying low-level cloud-top radiative cooling and subsequent cloudiness, thereby affecting aerosol semi-direct effects.

Study Configuration

• Spatial Scale: Northeast Atlantic Ocean (centered at approximately 17.49°N, 27.77°W) and Southeast Atlantic Ocean (centered at approximately 16.78°S, 8.90°E). Analysis domain divided into 5°×5° grid boxes.
• Temporal Scale: Ten years (2007–2017). Dust analysis focused on May to August, and smoke analysis on July to October.

Methodology and Data

• Models used:
  • BugRad radiative transfer model (part of CloudSat-CALIPSO 2B-FLXHR-LIDAR product).
  • Santa Barbara DISORT (Discrete Ordinate Radiative Transfer) Atmospheric Radiative Transfer (SBDART) model for sensitivity experiments.
• Data sources:
  • Satellite: CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) Level 2 data products (5 km aerosol profile, 5 km merged layer) for aerosol type, layer boundaries, optical depth at 532 nm, and extinction profiles.
  • Satellite: CloudSat for cloud cover, radiative flux, and associated radiative heating data (2B-FLXHR-LIDAR product).
  • Satellite: Aqua and Terra MODIS products for cloud data (used in Figure 1).
  • Reanalysis: European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset (ECMWF-AUX product) for background meteorological conditions (pressure, temperature, specific humidity, ozone mixing ratio).
  • Field campaign: ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) for smoke optical properties.

Main Results

• Elevated dust and smoke layers induce longwave-dominated warming responses that weaken the mean radiative cooling at low-level cloud tops.
• The pathways of this warming response differ: dust properties dominate dust-induced warming through direct longwave interactions, while smoke-induced warming involves enhanced smoke-layer moisture.
• Dust layers impact cloud-top cooling approximately ten times more strongly than smoke layers.
• Dust-induced longwave warming at the maximum radiative cooling level (1.68 km) is 0.34 ± 0.18 K day⁻¹, accounting for approximately a 16% reduction in mean cloud-top cooling. Smoke-induced warming is significantly smaller at 0.025 ± 0.018 K day⁻¹.
• This weakened cloud-top cooling response reduces low-level cloudiness by approximately 1.21% for dust and 0.28% for smoke.
• The weakening of cloud-top radiative cooling is primarily driven by increased aerosol optical properties (optical depth) rather than aerosol-layer characteristics (geometric thickness, base altitude). A one-standard-deviation increase in dust optical depth (0.25) leads to a cloud-top warming of 0.52 ± 0.01 K day⁻¹, compared to 0.03 ± 0.02 K day⁻¹ for smoke (0.13).
• Aerosol-layer humidity plays a critical role, amplifying the dust-induced cloud-top warming response but counteracting the cloud-top cooling that would otherwise be strengthened by increases in smoke-layer properties.

Contributions

• Demonstrates the critical importance of accounting for longwave-mediated processes, in addition to traditional shortwave-dominated mechanisms, when estimating aerosol semi-direct effects.
• Provides a process-level understanding of aerosol semi-direct effects, specifically differentiating the mechanisms for dust and smoke aerosols based on their distinct properties and interactions.
• Highlights that dust-layer optical properties primarily drive dust-induced cloud-top heating, whereas the smoke-induced cloud-top response is more sensitive to the counterbalancing influence of smoke properties and smoke-layer humidity.
• Suggests that previous estimates of the negative aerosol semi-direct effect for smoke and dust may be overestimated if longwave effects and aerosol-layer humidity are not fully considered, potentially reducing their magnitude or even shifting them towards a positive (warming) effect.
• Identifies a mechanism broadly applicable beyond the Atlantic Ocean, indicating potential global impacts of above-cloud absorbing aerosol-induced changes in cloud-top radiative cooling.

Funding

• U.S. Department of Energy (DOE), Office of Science (award #DE-SC0024281).

Citation

@article{Pandey2026Dust,
  author = {Pandey, Satyendra K. and Adebiyi, Adeyemi A.},
  title = {Dust and smoke layers over the Atlantic Ocean weaken the underlying low-level cloud-top radiative cooling through different pathways},
  journal = {Communications Earth & Environment},
  year = {2026},
  doi = {10.1038/s43247-026-03183-x},
  url = {https://doi.org/10.1038/s43247-026-03183-x}
}