Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations. Braswell1', William J. Sacks2, Ernst Linder5, and David s. Schimel4‘Complex Systems Research Center, University of New Hampshire, Durham, NH 03824; 603-862-2264 (Tel), 603-862-0188 (Fax), rob.braswell@unh.edu:Department of Environmental Studies. Williams College. P.O. Box 632 Williamstown, MA 0126 Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations7Department of Mathematics and Statistics, University of New Hampshire, Durham. NH 038244Climate and Global Dynamics Division, National Center for AtmEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
ospheric Research, P.O. Box 3000, Boulder, co 80305'Corresponding AuthorKeywords: Net Ecosystem Exchange (NEE), parameter estimation, data assimilatioEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsractWe performed a synthetic analysis of Harvard Forest NEE time series and a simple ecosystem carbon flux model, S1PNET. SIPNET runs at a half-daily time step, and has two vegetation carbon pools, a single aggregated soil carbon pool, and a simple soil moisture sub-model. We used a stochastic Bayes Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsian parameter estimation technique that provided posterior distributions of the model parameters, conditioned on the observed fluxes and the model equEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
ations. In this analysis, we estimated the values of all quantities that govern model behavior, including both rate constants and initial conditions fEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations information about process controls can be derived directly from the NEE observations. A wavelet decomposition technique enabled US to assess model performance at multiple time scales from diurnal to decadal. The mode) parameters are most highly constrained by eddy flux data at daily to seasonal tim Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationse scales, suggesting that this approach is not useful for calculating annual integrals. However, the ability of the model to fit both the diurnal andEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
seasonal variability patterns in the data simultaneously, using the same parameter set, indicates the effectiveness of this parameter estimation methoEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsel, and suggest several next steps in model development and observations for improved synthesis of models with flux observations.1. IntroductionDirect measurements of Nel Ecosystem Exchange of co. (NEE) using eddy covariance provide clear evidence (hat carbon fluxes arc responsive to a range of cnvứ Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsonmenlal factors. NEE data document the sensitivity of fluxes to both site conditions and climatic variability (Law el al. 2003; Gouiden el al. 1996).Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
However, because NEL is the difference between photosynthesis and rcspừalion, direct inference of process controls from flux data remains a technicalEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsdetermine how much information about stale variables (such as leaf area), rate constants (such as temperature coefficients) and thresholds (such as critical temperatures for photosynthesis) can be obtained directly and simultaneously from the eddy covariance record.We analyzed the decadal Harvard Fo Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsrest record using a model-data synthesis or "data assimilation” approach, combining observations with an ecosystem model. The model we used in this stEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
udy is based on the PnET family of ecosystem models (Aber & Federer 1992). which was designed to operate with eddy flux data (Aber el al. 1996). In thEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsizing the deviation between observed and simulated fluxes. Initial conditions and simulation of state variables can have significant effects on models results, especially in biogeochemistry, where currently most attention is focused on rate constant estimation (e.g, Giardina & Ryan 2000). Recognizin Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsg this, we placed as much emphasis on estimating the initial carbon pools as on estimating the other model parameters.In performing the parameter estiEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
mation, we used a Bayesian approach. The cornerstone of Bayesian statistics is Bayes' theorem (Gelman er al. 1995). which provides a mechanism for obtEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationssumed prior parameter distributions. Recent advances, enabled by increasing computer power, such as the application of Markov Chain Monte Carlo methods, have provided a solution to the problem of searching high dimensional parameter spaces. In this approach, ecosystem model parameters and data uncer Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationstainty are all treated as probability distributions. Conclusions about the information content of the data and about model validity are made by inspecEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
tion of the posterior distributions.The relative importance of different ecosystem processes varies from diurnal to seasonal to inlerannual lime scaleEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationss to estimate the role of processes operating al multiple lime scales through stale and parameter estimation techniques (Luo el al. 2001; Vukiccvic el al. 2001). and flux data arc increasingly being used to make inferences about controls over processes on these multiple time scales (e.g. Baldocchi & Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations Wilson 2001). rhe Harvard Forest eddy covariance data record, the longest such record available, should contain information about controls over carboEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
n fluxes on all these time scales. Inferences about controls on the diurnal time scale arc relatively straightforward since they can draw on many obseEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations(Goulden et al. 1996). aggravated by the smaller number of "replicate” seasonal and year-to-year patterns than daily cycles. As we obtain longer records of NEE from eddy covariance sites, this uncertainty will gradually diminish.The impact of the data on parameters governing different time scales an Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsd the goodness of fit on different time scales can be analyzed after assimilation into a model. This type of analysis combines empirical analysis of'Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
the data with comparison of the data to theory, as embodied in the model structure. We present a systematic analysis of model performance on multiple Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations of the ecosystem carbon flux model, and the parameter estimation scheme. Two overarching design constraints affected all aspects of the experiment. First, we chose to perform the analyses at a half-daily time step. Thus, the model and data were designed to consider each alternating daylight and nig Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationshttime interval as two discrete steps, with the length of each time step based on a calculation of sunrise and sunset times. This condition fixes theEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
overall data volume, and to some extent the degree of process-level aggregation. However, the daytime and nighttime points were considered together, aEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsl. 1998) or longer (e.g. Raich er al. 1991; Potter er al. 1993). Using a half-daily time step, however, gives time steps in which photosynthesis is not occurring, and thus the only carbon fluxes are from respiration. This facilitates the separation of respiration processes from photosynthesis in the Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations data assimilation, since nighttime data provide leverage on only the respiration-related parameters. Second, we chose to begin with a model that reprEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
esents relatively few processes, so that we could easily evaluate the degree to which the data provide leverage on the parameterization of each procesEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange ObservationsBobby H. Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations wind velocity and CO; concentration (Baldocchi er al. 1988). Though there is now a global network of these tower-based monitoring sites, the longest record is available at the Harvard Forest Long Term Ecological Research tLTER) site near Petersham. Massachusetts. USA (Wofsy et al. 1993: Goulden et Estimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observationsal. 1996). Starting in late 1991. quality-controlled estimates of NEE have been available at hourly time intervals, along with a suite of other meteorEstimating Diurnal to Annual Ecosystem Parameters by Synthesis of a Carbon Flux Model with Eddy Covariance Net Ecosystem Exchange Observations
ological variables. In our analysis, we used the hourly observations of eddy flux, canopy CO; storage, humidity, photosynthetically active radiation (Gọi ngay
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