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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2512.24202 |
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| _version_ | 1866915953843896320 |
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| author | Chagnaud, Guillaume Taylor, Chris M Jackson, Lawrence S Barber, Anne Burns, Helen Marsham, John H Birch, Cathryn E |
| author_facet | Chagnaud, Guillaume Taylor, Chris M Jackson, Lawrence S Barber, Anne Burns, Helen Marsham, John H Birch, Cathryn E |
| contents | Soil moisture is a key ingredient of humid heat through supplying moisture and modifying boundary layer properties. Soil moisture heterogeneity due to e.g., antecedent rainfall, can strongly influence weather patterns; yet, its effect on humid heat is poorly understood. Idealized numerical simulations are performed with a cloud-resolving ($Δx$=500 m), coupled land-atmosphere model wherein wet patches on length-scales $λ\in$ 25-150 km are prescribed. Compared to experiments with uniform soil moisture, humid heat is locally amplified by 1-4$^\circ$C, with maximum amplification for the critical soil moisture length-scale $λ_c=$ 50 km. Subsidence associated with a soil moisture-induced mesoscale circulation concentrates warm, humid air in a shallower boundary layer. The background wind and the magnitude of the wet-dry contrast control the relationship between $λ_c$ and the humid heat amplification. Based on observed soil moisture patterns, these results will help to predict extreme humid heat at city and county scales across the Tropics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_24202 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Mesoscale soil moisture heterogeneity can locally amplify humid heat Chagnaud, Guillaume Taylor, Chris M Jackson, Lawrence S Barber, Anne Burns, Helen Marsham, John H Birch, Cathryn E Atmospheric and Oceanic Physics Soil moisture is a key ingredient of humid heat through supplying moisture and modifying boundary layer properties. Soil moisture heterogeneity due to e.g., antecedent rainfall, can strongly influence weather patterns; yet, its effect on humid heat is poorly understood. Idealized numerical simulations are performed with a cloud-resolving ($Δx$=500 m), coupled land-atmosphere model wherein wet patches on length-scales $λ\in$ 25-150 km are prescribed. Compared to experiments with uniform soil moisture, humid heat is locally amplified by 1-4$^\circ$C, with maximum amplification for the critical soil moisture length-scale $λ_c=$ 50 km. Subsidence associated with a soil moisture-induced mesoscale circulation concentrates warm, humid air in a shallower boundary layer. The background wind and the magnitude of the wet-dry contrast control the relationship between $λ_c$ and the humid heat amplification. Based on observed soil moisture patterns, these results will help to predict extreme humid heat at city and county scales across the Tropics. |
| title | Mesoscale soil moisture heterogeneity can locally amplify humid heat |
| topic | Atmospheric and Oceanic Physics |
| url | https://arxiv.org/abs/2512.24202 |