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Abstract Evidence is mounting that temperate‐zone reforestation cools surface temperature (Tsurf), mitigating deleterious effects of climate warming. WhileTsurfdrives many biophysical processes, air temperature (Ta) is an equally important target for climate mitigation and adaptation. Whether reductions inTsurftranslate to reductions inTaremains complex, fraught by several nonlinear and intertwined processes. In particular, forest canopy structure strongly affects near‐surface temperature gradients, complicating cross‐site comparison. Here the influence of reforestation onTais assessed by targeting temperature metrics that are less sensitive to local canopy effects. Specifically, we consider the aerodynamic temperature (Taero), estimated using a novel procedure that does not rely on the assumptions of Monin‐Obukhov similarity theory, as well as the extrapolated temperature into the surface layer (Textrap). The approach is tested with flux tower data from a grass field, pine plantation, and mature hardwood stand co‐located in the Duke Forest (North Carolina, USA). During growing season daytime periods,Tsurfis 4–6 °C cooler, andTaeroand near‐surfaceTextrapare 2–3 °C cooler, in the forests relative to the grassland. During the dormant season, daytime differences are smaller but still substantial. At night, differences inTaeroare small, and near‐surfaceTextrapis warmer over forests than grasslands during the growing season (by 0.5 to 1 °C). Finally, the influence of land cover onTextrapat the interface between the surface and mixed layer is small. Overall, reforestation appears to provide a meaningful opportunity for adaption to warmer daytimeTain the southeastern United States, especially during the growing season.
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A practical exploration of land cover impacts on surface and air temperature when they are most consequential
Abstract Widespread shifts in land cover and land management (LCLM) are being incentivized as tools to mitigate climate change, creating an urgent need for prognostic assessments of how LCLM impacts surface energy balance and temperature. Historically, observational studies have tended to focus on how LCLM impacts surface temperature (Tsurf), usually at annual timescales. However, understanding the potential for LCLM change to confer climate adaptation benefits, or to produce unintended adverse consequences, requires careful consideration of impacts on bothTsurfand the near-surface air temperature (Ta,local) when they are most consequential for ecosystem and societal well-being (e.g. on hot summer days). Here, long-term data from 130 AmeriFlux towers distributed between 19–71 °N are used to systematically explore LCLM impacts on bothTsurfandTa,local, with an explicit focus on midday summer periods when adaptive cooling is arguably most needed. We observe profound impacts of LCLM onTsurfat midday, frequently amounting to differences of 10 K or more from one site to the next. LCLM impacts onTa,localare smaller but still significant, driving variation of 5–10 K across sites. The magnitude of LCLM impacts on bothTsurfandTa,localis not well explained by plant functional type, climate regime, or albedo; however, we show that LCLM shifts that enhance ET or increase canopy height are likely to confer a local mid-day cooling benefit for bothTsurfandTa,localmost of the time. At night, LCLM impacts on temperature are much smaller, such that averaging across the diurnal cycle will underestimate the potential for land cover to mediate microclimate when the consequences for plant and human well-being are most stark. Finally, during especially hot periods, land cover impacts onTa,localandTsurfare less coordinated, and ecosystems that tend to cool the air during normal conditions may have a diminished capacity to do so when it is very hot. We end with a set of practical recommendations for future work evaluating the biophysical impacts and adaptation potential of LCLM shifts.
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- Award ID(s):
- 2206086
- PAR ID:
- 10410791
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research: Climate
- Volume:
- 2
- Issue:
- 2
- ISSN:
- 2752-5295
- Page Range / eLocation ID:
- Article No. 025007
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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