[1] The Bayesian probability inversion and a Markov chain Monte Carlo (MCMC) technique were applied to a terrestrial ecosystem model to analyze uncertainties of estimated carbon (C) transfer coefficients and simulated C pool sizes. This study used six data sets of soil respiration, woody biomass, foliage biomass, litterfall, C content in the litter layers, and C content in mineral soil measured under both ambient CO 2 (350 ppm) and elevated CO 2 (550 ppm) plots from 1996 to 2000 at the Duke Forest FreeAir CO 2 Experiment (FACE) site. A Metropolis-Hastings algorithm was employed to construct a posterior probability density function (PPDF) of C transfer coefficients on the basis of prior information of model parameters, model structure, and the six data sets. The constructed PPDFs indicated that the transfer coefficients from pools of nonwoody biomass, woody biomass, and structural litter were well constrained by the six data sets under both ambient and elevated CO 2 . The data sets also gave moderate information to the transfer coefficient from the slow soil C pool. However, the transfer coefficients from pools of metabolic litter, microbe, and passive soil C were poorly constrained. The poorly constrained parameters were attributable to either the lack of experimental data or the mismatch of timescales between the available data and the parameters to be estimated. Cumulative distribution functions were constructed for simulated C pool sizes on the basis of the six data sets, showing that on average the ecosystem would store 16,616 g C m À2at elevated CO 2 by the year 2010, significantly higher than 13,426 g C m À2 at ambient CO 2 with 95% confidence. This study shows that the combination of a Bayesian approach and MCMC inversion technique is an effective method to synthesize information from various sources for assessment of ecosystem responses to elevated CO 2 .

[1] A sound understanding of the sustainability of terrestrial carbon (C) sequestration is critical for the success of any policies geared toward stabilizing atmospheric greenhouse concentrations. This includes the Kyoto Protocol and/or other greenhouse strategies implemented by individual countries. However, the sustainability of C sinks and pools has not been carefully studied with either empirical or theoretical approaches. This study was intended to develop a conceptual framework to define the sustainability based on C influx and residence time (t). The latter t quantifies the capacity for C storage in various plant and soil pools. We estimated t via inverse analysis of multiple data sets from a Free-Air CO 2 Enrichment (FACE) experiment in Duke Forest, North Carolina, United States. This study suggested that estimated residence times at elevated CO 2 decreased for plant C pools and increased for litter and soil pools in comparison to those at ambient CO 2 . The ensemble of the residence times from all the pools at elevated CO 2 , however, was well correlated with that at ambient CO 2 . We then used the estimated residence times, combined with C influx, to simulate C sequestration rates in response to a gradual increase in atmospheric CO 2 concentration (C a ). The simulated C sequestration rate gradually increased from 69 g m À2 yr À1 in 2000 when C a was 378 ppm to 201 g m À2 yr À1 in 2100 when C a was at 710 ppm. Thus, the current evidence from both experimental observations and inverse analysis suggested that C sequestration in the forest ecosystem was likely to increase gradually as C a gradually increases. The model projection of the C sequestration will improve as more data on long-term processes become available in coming years. In addition, such a modeled increase in terrestrial C sequestration is too small to balance the anthropogenic C emission.

Quantification of the flux of carbon (C) through different pathways is critical to predict the impact of global change on terrestrial ecosystems. Past research has encountered considerable difficulty in separating root exudation, root turnover rate, and other belowground C fluxes as affected by elevated CO 2 . In this study we adopted a deconvolution analysis to differentiate C flux pathways in forest soils and to quantify the flux through those pathways. We first conducted forward analysis using a terrestrial-C sequestration (TCS) model to generate four alternative patterns of convolved responses of soil surface respiration to a step increase in atmospheric CO 2 . The model was then validated against measured soil respiration at ambient CO 2 before it was used to deconvolve the CO 2 stimulation of soil respiration. Deconvolved data from the Duke Forest free-air CO 2 enrichment (FACE) experiment suggest that fast C transfer processes, e.g., root exudation, are of minor importance in the ecosystem C cycling in the Duke Forest and were not affected by elevated CO 2 . The analysis indicates that the fine-root turnover is a major process adding C to the rhizosphere. This C has a residence time of several months to ϳ2 yr and increases significantly with increased CO 2 . In addition, the observed phase shift in soil respiration caused by elevated CO 2 can be only reproduced by incorporation of a partial time delay function in C fluxes into the model. This paper also provides a detailed explanation of deconvolution analysis, since it is a relatively new research technique in ecology.

A new parametric model of vortex tangential-wind profiles is presented that is primarily designed to depict realistic-looking tangential wind profiles such as those in intense atmospheric vortices arising in dust devils, waterspouts, tornadoes, mesocyclones, and tropical cyclones. The profile employs five key parameters: maximum tangential wind, radius of maximum tangential wind, and three power-law exponents that shape different portions of the velocity profile. In particular, a new parameter is included controlling the broadly or sharply peaked profile in the annular zone of tangential velocity maximum. Different combinations of varying the model parameters are considered to investigate and understand their effects on the physical behaviors of tangential wind and corresponding vertical vorticity profiles. Additionally, the parametric tangential velocity and vorticity profiles are favorably compared to those of an idealized Rankine model and also those of a theoretical stagnant core vortex model in which no tangential velocity exists within a core boundary and a potential flow occurs outside the core. Furthermore, the parametric profiles are evaluated against and compared to those of two other idealized vortex models (Burgers-Rott and Sullivan). The comparative profiles indicate very good agreements with low root-mean-square errors of a few tenths of a meter per second and high correlation coefficients of nearly one. Thus, the veracity of the parametric model is demonstrated.

A new parametric tropical cyclone (TC) wind profile model is presented for depicting representative surface pressure profiles corresponding to multiple-maxima wind profiles that exhibit single-, dual-, and triplemaximum concentric-eyewall wind peaks associated with the primary (inner), secondary (first outer), and tertiary (second outer) complete rings of enhanced radar reflectivity. One profile employs five key parameters: tangential velocity maximum, radius of the maximum, and three different shape velocity parameters related to the shape of the profile. After tailoring the model for TC applications, a gradient wind is computed from a cyclostrophic wind formulated in terms of the cyclostrophic Rossby number. A pressure, via cyclostrophic balance, was partitioned into separate pressure components that corresponded to multiple-maxima cyclostrophic wind profiles in order to quantitatively evaluate the significant fluctuations in central pressure deficits. The model TC intensity in terms of varying growth, size, and decay velocity profiles was analyzed in relation to changing each of five key parameters. Analytical results show that the first shape velocity parameter, changing a sharply to broadly peaked wind profile, increases the TC intensity and size by producing the corresponding central pressure fall. An increase (decrease) in the second (third) shape velocity parameter yields the pressure rise (fall) by decreasing (increasing) the inner (outer) wind profile inside (outside) the radius of the maximum. When a single-maximum tangential wind profile evolves to multiple-maxima tangential wind profiles during an eye replacement cycle, the pressure falls and rises are sensitively fluctuated.