Impacts of wind farms on land surface temperature

Zhou, Liming; Tian, Yuhong; Roy, Somnath Baidya; Thorncroft, Chris D.; Bosart, Lance F.; Hu, Yuting

doi:10.1038/nclimate1505

Cited by 245 publications

(215 citation statements)

References 25 publications

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“…. Further, the use of the roughness approach generates turbine-induced daytime heating and nocturnal cooling (Fitch et al 2013b) rather than the observed nocturnal heating (Zhou et al 2012;Rajewski et al 2013Rajewski et al , 2014. Alternatively, the fact that the turbine rotor disk is elevated is considered by using flow-dependent parameters to introduce the effects of turbines into the flow, resulting in turbine-induced elevated drag and an increase in turbulence intensity.…”

Section: Turbine-wake Simulationsmentioning

confidence: 99%

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Lee

Lundquist

2017

Boundary-Layer Meteorol

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Wind-turbine-wake evolution during the evening transition introduces variability to wind-farm power production at a time of day typically characterized by high electricity demand. During the evening transition, the atmosphere evolves from an unstable to a stable regime, and vertical stratification of the wind profile develops as the residual planetary boundary layer decouples from the surface layer. The evolution of wind-turbine wakes during the evening transition is examined from two perspectives: wake observations from single turbines, and simulations of multiple turbine wakes using the mesoscale Weather Research and Forecasting (WRF) model. Throughout the evening transition, the wake's wind-speed deficit and turbulence enhancement are confined within the rotor layer when the atmospheric stability changes from unstable to stable. The height variations of maximum upwind-downwind differences of wind speed and turbulence intensity gradually decrease during the evening transition. After verifying the WRF-model-simulated upwind wind speed, wind direction and turbulent kinetic energy profiles with observations, the wind-farm-scale wake evolution during the evening transition is investigated using the WRF-model wind-farm parametrization scheme. As the evening progresses, due to the presence of the wind farm, the modelled hub-height wind-speed deficit monotonically increases, the relative turbulence enhancement at hub height grows by 50%, and the downwind surface sensible heat flux increases, reducing surface cooling. Overall, the intensifying wakes from upwind turbines respond to the evolving atmospheric boundary layer during the evening transition, and undermine the power production of downwind turbines in the evening.

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Section: Turbine-wake Simulationsmentioning

confidence: 99%

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Lee

Lundquist

2017

Boundary-Layer Meteorol

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“…LST during the daytime is controlled by incoming solar radiation, surface properties (such as albedo and emissivity), partitioning of latent and sensible heat fluxes, and mixing in the near-surface atmospheric boundary layer (16). Incoming solar radiation can be assumed to be similar between adjacent PF and GR or CR pixels.…”

Section: Significancementioning

confidence: 99%

“…These LST data depend on the radiative properties of the land surface (15,16) and, therefore, have a larger diurnal amplitude than the standard 2-m air temperature data from meteorological stations (17). The primary objective of this investigation is to quantify the space-time distribution of differences in LST between PF and adjacent GR or CR (ΔLST), during both daytime and nighttime.…”

mentioning

confidence: 99%

Afforestation in China cools local land surface temperature

Peng

Piao

Zeng

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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571

402

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China has the largest afforested area in the world (∼62 million hectares in 2008), and these forests are carbon sinks. The climatic effect of these new forests depends on how radiant and turbulent energy fluxes over these plantations modify surface temperature. For instance, a lower albedo may cause warming, which negates the climatic benefits of carbon sequestration. Here, we used satellite measurements of land surface temperature (LST) from planted forests and adjacent grasslands or croplands in China to understand how afforestation affects LST. Afforestation is found to decrease daytime LST by about 1.1 ± 0.5°C (mean ± 1 SD) and to increase nighttime LST by about 0.2 ± 0.5°C, on average. The observed daytime cooling is a result of increased evapotranspiration. The nighttime warming is found to increase with latitude and decrease with average rainfall. Afforestation in dry regions therefore leads to net warming, as daytime cooling is offset by nighttime warming. Thus, it is necessary to carefully consider where to plant trees to realize potential climatic benefits in future afforestation projects. T he area of planted forest (PF) in China has increased by ∼1.7 million hectares per year (about 41% of the global afforestation rate) during the last 2 decades (1, 2). China had the largest PF area in the world in 2008, at ∼62 million hectares ( Fig. 1), or ∼23% of global plantation area (264 million hectares) (1, 2). The Chinese government launched several projects to convert croplands (CR) and marginal lands into forests, to reduce soil and water quality degradation, in the 1980s and 1990s (2). This afforestation contributed to increased carbon storage (3, 4) but also altered local energy budgets, which has the potential to offer feedback on local and regional climates (5-10).Forests generally have a lower albedo than grasslands (GR) and CR. Thus, afforestation increases the amount of absorbed solar radiation at the surface (9, 10). Surface cooling will result if this extra energy is dissipated as evapotranspiration (ET) (11) or heat convection (7); otherwise, afforestation will result in surface warming. The biophysical effects of afforestation on local climate can be much larger than the small global cooling effect resulting from uptake of CO 2 by growing forests (8,12,13). However, these biophysical effects are also complex and depend on "background" climate (14). Afforestation generally cools the surface in tropical areas but warms it in boreal lands (6,(8)(9)(10). The effects of afforestation in temperate regions are not clear. The large area under afforestation in China, the diversity of projects (over former CR, GR, or marginal lands), and the broad range of background climates (most plantations are in temperate regions with varying degrees of annual average rainfall) provide an interesting test bed to assess how afforestation affects local temperature.In this article, we investigate how plantations affect land surface temperature (LST) across China, using satellite-derived LST data sets from Earth Observin...

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“…Jacobson and Archer (2012) also use the latter approach, but neglect direct TKE production in favour of an implicit source resulting from the wind shear in the wake layer. Fitch et al (2013b) demonstrated the benefits of using an elevated drag approach over a roughness length modification; simulated diurnal cycles of wind-speed deficit, TKE, and temperature change were reversed between the two approaches, with the elevated drag approach matching the few studies of wind-farm wakes currently available (Christiansen and Hasager 2005;Baidya Roy and Traiteur 2010;Zhou et al 2012). Though the aforementioned studies yield insight into wind-turbine impacts on the atmospheric diurnal cycle, our knowledge of interactions between wind farms and the land surface remains primitive.…”

Section: Introductionmentioning

confidence: 99%

“…By necessity, most wind farms in these states are located on existing cropland. Therefore, wind turbines have the potential to alter crop growth through the modification of surface fluxes of heat and moisture (Zhou et al 2012;Harris et al 2014). Conversely, crop growth and harvesting cycles modify local surface properties, the effects of which can influence the wind resource aloft (e.g., changes to the rotor-layer wind speed, wind shear, and vertical momentum fluxes).…”

Section: Introductionmentioning

confidence: 99%

Could Crop Height Affect the Wind Resource at Agriculturally Productive Wind Farm Sites?

Vanderwende

Lundquist

2015

Boundary-Layer Meteorol

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The collocation of cropland and wind turbines in the US Midwest region introduces complex meteorological interactions that could influence both agriculture and wind-power production. Crop management practices may affect the wind resource through alterations of land-surface properties. We use the weather research and forecasting (WRF) model to estimate the impact of crop height variations on the wind resource in the presence of a large turbine array. A hypothetical wind farm consisting of 121 1.8-MW turbines is represented using the WRF model wind-farm parametrization. We represent the impact of selecting soybeans rather than maize by altering the aerodynamic roughness length in a region approximately 65 times larger than that occupied by the turbine array. Roughness lengths of 0.1 and 0.25 m represent the mature soy crop and a mature maize crop, respectively. In all but the most stable atmospheric conditions, statistically significant hub-height wind-speed increases and rotor-layer wind-shear reductions result from switching from maize to soybeans. Based on simulations for the entire month of August 2013, wind-farm energy output increases by 14 %, which would yield a significant monetary gain. Further investigation is required to determine the optimal size, shape, and crop height of the roughness modification to maximize the economic benefit and minimize the cost of such crop-management practices. These considerations must be balanced by other influences on crop choice such as soil requirements and commodity prices.

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Impacts of wind farms on land surface temperature

Cited by 245 publications

References 25 publications

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Afforestation in China cools local land surface temperature

Could Crop Height Affect the Wind Resource at Agriculturally Productive Wind Farm Sites?

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