Luo et al. (2026) Cropland biophysical impacts on land surface temperature show diurnal differences across tropical Africa

Identification

• Journal: Communications Earth & Environment
• Year: 2026
• Date: 2026-04-02
• Authors: Hao Luo, Johannes Quaas
• DOI: 10.1038/s43247-026-03445-8

Research Groups

• Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany
• German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany

Short Summary

This study quantifies the diurnal biophysical impacts of cropland expansion on land surface temperature across tropical Africa, revealing consistent nighttime cooling and hydroclimatically-dependent daytime effects (cooling in arid, warming in less arid regions) driven by turbulent heat flux changes linked to leaf area index.

Objective

• To quantify the diurnal-scale biophysical impacts of cropland expansion on land surface temperature (Ts) across tropical Africa.
• To investigate the underlying biophysical mechanisms driving these impacts.
• To assess the role of background hydroclimatic conditions in modulating cropland biophysical impacts on Ts.

Study Configuration

• Spatial Scale: Tropical Africa, at a resolution of 0.05° × 0.05°.
• Temporal Scale: 17 years (2004–2020) of hourly observations.

Methodology and Data

• Models used:
  • Space-for-time substitution approach
  • Physics-based hourly linear attribution framework
  • Structural Equation Modelling (SEM)
• Data sources:
  • Geostationary satellite observations: Meteosat Second Generation (MSG) from EUMETSAT LSA SAF products (Ts, surface albedo (α), surface downward shortwave radiation (S↓), surface downward longwave radiation (L↓), sensible heat flux (H), latent heat flux (LE), surface emissivity, leaf area index (LAI)); CM SAF LANDFLUX Ed. 1 (ground heat flux (G)); CM SAF CLAAS-3 (cloud fraction); CM SAF SARAH-3 (effective cloud albedo).
  • Polar-orbiting satellite data: MODIS/Terra Ts product (MOD11C3, version 061); MODIS land cover type product (MCD12C1, version 061).
  • Validation data: FLUXCOM-RS (LE and H).
  • Ancillary data: Shuttle Radar Topography Mission (SRTM) DEM (version 4); Climate Research Unit (CRU) TS v4.08 datasets (precipitation, potential evapotranspiration for Humidity Index).

Main Results

• Croplands consistently cool the surface at night relative to surrounding grasslands across tropical Africa.
• Daytime cropland biophysical impacts on Ts (ΔTs) are strongly dependent on hydroclimatic conditions:
  • Cooling effects are observed in more arid regions (Humidity Index < 0.4).
  • Warming effects are observed in less arid regions (Humidity Index > 0.4).
• The strongest diurnal differences in ΔTs across hydroclimatic regimes occur at 12:00 Local Solar Time (LST).
• Cropland-induced changes in turbulent heat fluxes (ΔH + ΔLE) are the dominant explanatory components of ΔTs.
• Changes in surface albedo (Δα) act as a buffering mechanism during daytime, promoting warming in more arid regions and cooling in less arid regions.
• These biophysical changes are primarily linked to differences in leaf area index (ΔLAI) between croplands and grasslands, with ΔLAI generally higher in more arid regions (potentially due to irrigation) and lower in less arid regions.
• Structural Equation Modelling (SEM) indicates that ΔTs is primarily consistent with ΔLE in both day and night; nighttime ΔLE is largely linked to ΔLAI, while daytime ΔLE is directly associated with ΔLAI and indirectly modulated by Δα.

Contributions

• Provides the first comprehensive quantification of the diurnal cycles of cropland biophysical impacts on land surface temperature across tropical Africa using 17 years of geostationary satellite observations.
• Offers a mechanistic understanding of how cropland expansion alters local climate across hydroclimatic gradients, explicitly considering diurnal variations and the modulating role of background hydroclimatic conditions.
• Highlights the potential risk of intensified daytime warming associated with cropland expansion in less arid regions of tropical Africa.
• Utilizes a physics-based hourly linear attribution framework and structural equation modeling to disentangle the complex biophysical pathways.

Funding

• Projekt DEAL

Citation

@article{Luo2026Cropland,
  author = {Luo, Hao and Quaas, Johannes},
  title = {Cropland biophysical impacts on land surface temperature show diurnal differences across tropical Africa},
  journal = {Communications Earth & Environment},
  year = {2026},
  doi = {10.1038/s43247-026-03445-8},
  url = {https://doi.org/10.1038/s43247-026-03445-8}
}