Modeling feedbacks between a boreal forest and the planetary boundary layer

Hill, Timothy; Williams, Mathew; Moncrieff, John

doi:10.1029/2007jd009412

Cited by 16 publications

(15 citation statements)

References 82 publications

(72 reference statements)

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“…This interpretation is applicable to the entire range of incoming radiation and early-morning temperatures. All in all, the sensitivity of the system to roughness is relatively low compared to the other properties, which is in line with the previous findings of Hill et al (2008).…”

Section: Unraveling the Feedback Mechanismssupporting

confidence: 81%

“…Since forest has a lower value, it has a lower stomatal resistance under unstressed conditions and therefore higher evapotranspiration rates ( 50 W m −2 more than grassland). Hill et al (2008) have already pointed out the importance of the leaf-area index. The higher evapotranspiration rate results in significantly lower maximum temperatures over forest (more than 1.2 K less than grassland).…”

Section: Unraveling the Feedback Mechanismsmentioning

confidence: 99%

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Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land–atmosphere coupling

Heerwaarden

Teuling

2014

Biogeosciences

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Abstract. This study investigates the difference in land-atmosphere interactions between grassland and forest during typical heatwave conditions in order to understand the controversial results of Teuling et al. (2010) (hereafter T10), who found the systematic occurrence of higher sensible heat fluxes over forest than over grassland during heatwaves. With a simple but accurate coupled land-atmosphere model, we show that existing parametrizations are able to reproduce the findings of T10 for normal summer and heatwave conditions. Furthermore, we demonstrate the sensitivity of the coupled system to changes in incoming radiation and early-morning temperature typical for European heatwaves.Our results suggest that the fast atmospheric control of stomatal resistance can explain the observed differences between grassland and forest. The atmospheric boundary layer has a buffering function therein: increases in stomatal resistance are largely compensated for by increases in the potential evaporation due to atmospheric warming and drying.In order to disentangle the contributions of differences in several static and dynamic properties between forest and grassland, we have performed a virtual experiment with artificial land-use types that are equal to grassland, but with one of its properties replaced by that of forest. From these, we confirm the important role of the fast physiological processes that lead to the closure of stomata. Nonetheless, for a full explanation of T10's results, the other properties (albedo, roughness and the ratio of minimum stomatal resistance to leaf-area index) play an important but indirect role; their influences mainly consist of strengthening the feedback that leads to the closure of the stomata by providing more energy that can be converted into sensible heat. The model experiment also confirms that, in line with the larger sensible heat flux, higher atmospheric temperatures occur over forest.As our parametrization for stomatal resistance is empirical rather than mechanical, our study stresses the demand for a better mechanistic understanding of physiological processes in plants.

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Section: Unraveling the Feedback Mechanismssupporting

confidence: 81%

Section: Unraveling the Feedback Mechanismsmentioning

confidence: 99%

Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land–atmosphere coupling

Heerwaarden

Teuling

2014

Biogeosciences

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“…The coupled atmosphere-biosphere (CAB) model (Hill et al 2008) is composed of two main components: a PBL model and a land surface exchange scheme. These models are the coupled atmospheric boundary layerplant-soil (CAPS) model which was based on the Oregon State University 1-dimensional planetary boundary layer (OSU1DPBL) model Pan 1984, Troen andMahrt 1986) and the soil-plant-atmosphere (SPA) model (Williams et al 1996(Williams et al , 2001a.…”

Section: The Cab Modelmentioning

confidence: 99%

“…We can thus determine the utility of data from different observations systems in constraining ecosystem states in landscapescale inversion problems. To achieve this we implement a coupled atmosphere-biosphere (CAB) model (Hill et al 2008) both on its own and as part of a Bayesian inversion scheme (Mosegaard andTarantola 1995, Knorr andKattge 2005). We drive the model in the normal ''forward'' mode using multi-scale data from the Boreal Ecosystem-Atmosphere Study (BOREAS; Sellers et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Constraining ecosystem processes from tower fluxes and atmospheric profiles

Hill

Williams

Woodward

et al. 2011

Ecological Applications

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Abstract. The planetary boundary layer (PBL) provides an important link between the scales and processes resolved by global atmospheric sampling/modeling and site-based flux measurements. The PBL is in direct contact with the land surface, both driving and responding to ecosystem processes. Measurements within the PBL (e.g., by radiosondes, aircraft profiles, and flask measurements) have a footprint, and thus an integrating scale, on the order of ;1-100 km. We use the coupled atmosphere-biosphere model (CAB) and a Bayesian data assimilation framework to investigate the amount of biosphere process information that can be inferred from PBL measurements.We investigate the information content of PBL measurements in a two-stage study. First, we demonstrate consistency between the coupled model (CAB) and measurements, by comparing the model to eddy covariance flux tower measurements (i.e., water and carbon fluxes) and also PBL scalar profile measurements (i.e., water, carbon dioxide, and temperature) from Canadian boreal forest. Second, we use the CAB model in a set of Bayesian inversions experiments using synthetic data for a single day. In the synthetic experiment, leaf area and respiration were relatively well constrained, whereas surface albedo and plant hydraulic conductance were only moderately constrained. Finally, the abilities of the PBL profiles and the eddy covariance data to constrain the parameters were largely similar and only slightly lower than the combination of both observations.

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“…Moreover, improved scaling between stand-level observations (e.g., flux towers) and larger scale satellite measurements also depends upon a clear understanding of the mechanisms controlling the coupled atmosphere-biosphere system (Hill et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Coupled Atmosphere-Biosphere Models as a Tool for Conservation Planning and Policy

Ladle

Malhado

Costa³

2011

Nat. Conserv.

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Over the last 20 years a new generation of climate models have been developed that link atmosphere models to dynamic vegetation models (coupled atmosphere-biosphere models). These models are able to capture key feedbacks between the changing climate and changing ecosystems, providing more realistic forecasts of anthropogenic climate change. Moreover, the biosphere model can be regionally calibrated to provide more geographically specific predictions about future trajectories of environmental change over the next century. We identify four potential uses of coupled atmosphere-biosphere models for conservation: (i) more accurate and regionally specific forecasts of climate change; (ii) better understanding of carbon cycling, a key ecosystem service; (iii) better placement and design of protected areas, and; (iv) improved modeling of different land-use scenarios. Realizing these objectives will require better integration and communication between modeling and conservation communities and the development of specific visualization and planning tools that allows these complex models to be fully integrated into conservation planning.

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Modeling feedbacks between a boreal forest and the planetary boundary layer

Cited by 16 publications

References 82 publications

Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land–atmosphere coupling

Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land–atmosphere coupling

Constraining ecosystem processes from tower fluxes and atmospheric profiles

Coupled Atmosphere-Biosphere Models as a Tool for Conservation Planning and Policy

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