Detecting regional variability in sources and sinks of carbon dioxide: a synthesis

The current paper reviews the experimental setup of the CarboEurope Experimental Strategy (CERES) campaigns with the aim of providing an overview of the instrumentation used, the data-set and associated modelling. It then assesses progress in the field of regional observation and modelling of carbon fluxes, bringing the papers of this special issue into a somewhat broader context of analysis. <br><br> Instrumental progress has been obtained in the field of remotely monitoring from tall towers and the experimental planning. Flux measurements from aircraft are now capable, within some constraints, to provide regular regional observations of fluxes of CO<sub>2</sub>, latent and sensible heat. <br><br> Considerable effort still needs to be put into calibrating the surface schemes of models, as they have direct impact on the input of energy, moisture and carbon fluxes in the boundary layer. Overall, the mesoscale models appear to be capable of simulating the large scale dynamics of the region, but in the fine detail, like the precise horizontal and vertical CO<sub>2</sub> field differences between the models still exist. These errors translate directly into transport uncertainty, when the forward simulations are used in inverse mode. Quantification of this uncertainty, including that of inadequate boundary layer height modelling, still remains a major challenge for state of the art mesoscale models. Progress in inverse models has been slow, but has shown that it is possible to estimate some of the errors involved, and that using the combination of observations. Overall, the capability to produce regional, high-resolution estimates of carbon exchange, exist in potential, but the routine application will require considerable effort, both in the experimental as in the modelling domain

A simple modeling approach to study the regional impact of a Mediterranean forest isoprene emission on anthropogenic plumes

Research during the past decades has outlined the importance of biogenic isoprene emission in tropospheric chemistry and regional ozone photo-oxidant pollution. The first part of this article focuses on the development and validation of a simple biogenic emission scheme designed for regional studies. Experimental data sets relative to Boreal, Tropical, Temperate and Mediterranean ecosystems are used to estimate the robustness of the scheme at the canopy scale, and over contrasted climatic and ecological conditions. A good agreement is generally found when comparing field measurements and simulated emission fluxes, encouraging us to consider the model suitable for regional application. Limitations of the scheme are nevertheless outlined as well as further on-going improvements. In the second part of the article, the emission scheme is used on line in the broader context of a meso-scale atmospheric chemistry model. Dynamically idealized simulations are carried out to study the chemical interactions of pollutant plumes with realistic isoprene emissions coming from a Mediterranean oak forest. Two types of anthropogenic sources, respectively representative of the Marseille (urban) and Martigues (industrial) French Mediterranean sites, and both characterized by different VOC/NOx are considered. For the Marseille scenario, the impact of biogenic emission on ozone production is larger when the forest is situated in a sub-urban configuration (i.e.&nbsp;downwind distance TOWN-FOREST <30km, considering an advection velocity of 4.2 m.s^-1). In this case the enhancement of ozone production due to isoprene can reach +37% in term of maximum surface concentrations and +11% in term of total ozone production. The impact of biogenic emission decreases quite rapidly when the TOWN-FOREST distance increases. For the Martigues scenario, the biogenic impact on the plume is significant up to TOWN-FOREST distance of 90km where the ozone maximum surface concentration enhancement can still reach +30%. For both cases, the importance of the VOC/NO_x ratio in the anthropogenic plume and its evolution when interacting with the forest emission are outlined. In complement to real case studies, this idealized approach can be particularly useful for process and sensitivity studies and constitutes a valuable tool to build regional ozone control strategies

Mesoscale covariance of transport and CO2 fluxes: Evidence from observations and simulations using the WRF-VPRM coupled atmosphere-biosphere model

We developed a modeling system which combines a mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, with a diagnostic biospheric model, the Vegetation Photosynthesis and Respiration (VPRM). The WRF-VPRM modeling system was designed to realistically simulate high-resolution atmospheric CO₂ concentration fields. In the system, WRF takes into account anthropogenic and biospheric CO₂ fluxes and realistic initial and boundary conditions for CO₂ from a global model. The system uses several “tagged” tracers for CO₂ fields from different sources. VPRM uses meteorological fields from WRF and high-resolution satellite indices to simulate biospheric CO₂ fluxes with realistic spatiotemporal patterns. Here we present results from the application of the model for interpretation of measurements made within the CarboEurope Regional Experiment Strategy (CERES). Simulated fields of meteorological variables and CO₂ were compared against ground-based and airborne observations. In particular, the characterization by aircraft measurements turned out to be crucial for the model evaluation. The comparison revealed that the model is able to capture the main observed features in the CO₂ distribution reasonably well. The simulations showed that daytime CO₂ measurements made at coastal stations can be strongly affected by land breeze and subsequent sea breeze transport of CO₂ respired from the vegetation during the previous night, which can lead to wrong estimates when such data are used in inverse studies. The results also show that WRF-VPRM is an effective modeling tool for addressing the near-field variability of CO₂ fluxes and concentrations for observing stations around the globe

CO2 budgeting at the regional scale using a Lagrangian experimental strategy and meso-scale modeling

An atmospheric Lagrangian experiment for regional CO2 budgeting with aircraft measurements took place during the CarboEurope Regional Experiment Strategy campaign (CERES) in south-west France, in June 2005. The atmospheric CO2 aircraft measurements taken upstream and downstream of an active and homogeneous pine forest revealed a CO2 depletion in the same air mass, using a Lagrangian strategy. This field experiment was analyzed with a meteorological meso-scale model interactively coupled with a surface scheme, with plant assimilation, ecosystem respiration, anthropogenic CO2 emissions and sea fluxes. First, the model was carefully validated against observations made close to the surface and in the atmospheric boundary layer. Then, the carbon budget was evaluated using the numerous CERES observations, by upscaling the surface fluxes observations, and using the modeling results, in order to estimate the relative contribution of each physical process. A good agreement is found between the two methods which use the same vegetation map: the estimation of the regional CO2 surface flux by the Eulerian meso-scale model budget is close to the budget deduced from the upscaling of the observed surface fluxes, and found a budget between −9.4 and −12.1μmol.m−2.s−1, depending on the size of the considered area. Nevertheless, the associated uncertainties are rather large for the upscaling method and reach 50%. A third method, using Lagrangian observations of CO2 estimates a regional CO2 budget a few different and more scattered, (−16.8μmol.m−2.s−1 for the small sub-domain and −8.6μmol.m−2.s−1 for the larger one). For this budgeting method, we estimate a mean of 31% error, mainly arising from the time of integration between the two measurements of the Lagrangian experiment. The paper describes in details the three methods to assess the regional CO2 budget and the associated error

Mesoscale modelling of the CO2 interactions between the surface and the atmosphere applied to the April 2007 CERES field experiment

This paper describes a numerical interpretation of the April 2007, CarboEurope Regional Experiment Strategy (CERES) campaign, devoted to the study of the CO2 cycle at the regional scale. Four consecutive clear sky days with intensive observations of CO2 concentration, fluxes at the surface and in the boundary layer have been simulated with the Meso-NH mesoscale model, coupled to ISBA-A-gs land surface model. The main result of this paper is to show how aircraft observations of CO2 concentration have been used to identify surface model errors and to calibrate the CO2 driving component of the surface model. In fact, the comparisons between modelled and observed CO2 concentrations within the Atmospheric Boundary Layer (ABL) allow to calibrate and correct not only the parameterization of respired CO2 fluxes by the ecosystem but also the Leaf Area Index (LAI) of the dominating land cover. After this calibration, the paper describes systematic comparisons of the model outputs with numerous data collected during the CERES campaign, in April 2007. For instance, the originality of this paper is the spatial integration of the comparisons. In fact, the aircraft observations of CO2 concentration and fluxes and energy fluxes are used for the model validation from the local to the regional scale. As a conclusion, the CO2 budgeting approach from the mesoscale model shows that the winter croplands are assimilating more CO2 than the pine forest, at this stage of the year and this case study

Bridging the gap between atmospheric concentrations and local ecosystem measurements

This paper demonstrates that atmospheric inversions of CO₂ are a reliable tool for estimating regional fluxes. We compare results of an inversion over 18 days and a 300 x 300 km 2 domain in southwest France against independent measurements of fluxes from aircraft and towers. The inversion used concentration measurements from 2 towers while the independent data included 27 aircraft transects and 5 flux towers. The inversion reduces the mismatch between prior and independent fluxes, improving both spatial and temporal structures. The present mesoscale atmospheric inversion improves by 30% the CO₂ fluxes over distances of few hundreds of km around the atmospheric measurement locations. Citation: Lauvaux, T., et al. (2009), Bridging the gap between atmospheric concentrations and local ecosystem measurements, Geophys. Res. Lett., 36, L19809, doi: 10.1029/2009GL039574

Search for Electron Neutrino Appearance in a 250 km Long-baseline Experiment

We present a search for electron neutrino appearance from accelerator produced muon neutrinos in the K2K long baseline neutrino experiment. One candidate event is found in the data corresponding to an exposure of 4.8*10^19 protons on target. The expected background in the absence of neutrino oscillations is estimated to be 2.4+-0.6 events and is dominated by mis-identification of events from neutral current pi^0 production. We exclude the \nu_\mu to \nu_e oscillations at 90% C.L. for the effective mixing angle in 2-flavor approximation of sin^2(2theta_\mu_e) (~= 1/2 sin^2 2 th_13) > 0.15 at Delta m^2_\mu_e = 2.8*10^{-3} eV^2, the best fit value of the \nu_\mu disappearance analysis in K2K. The most stringent limit of sin^2(2theta_\mu_e) < 0.09 is obtained at Delta m^2_\mu_e = 6*10^{-3} eV^2.Comment: 5 pages with 2 figures embeded in two column revtex4 style. Accepted to be published in Phys. Rev. Let

Solar neutrino measurements in Super-Kamiokande-I

The details of Super--Kamiokande--I's solar neutrino analysis are given. Solar neutrino measurement in Super--Kamiokande is a high statistics collection of $^8$B solar neutrinos via neutrino-electron scattering. The analysis method and results of the 1496 day data sample are presented. The final oscillation results for the data are also presented.Comment: 32pages, 57figures, submitted to Physical Review

Three flavor neutrino oscillation analysis of atmospheric neutrinos in Super-Kamiokande

We report on the results of a three-flavor oscillation analysis using Super-Kamiokande~I atmospheric neutrino data, with the assumption of one mass scale dominance ($\Delta m_{12}^2$$=$0). No significant flux change due to matter effect, which occurs when neutrinos propagate inside the Earth for $\theta_{13}$$\neq$0, has been seen either in a multi-GeV $\nu_e$-rich sample or in a $\nu_\mu$-rich sample. Both normal and inverted mass hierarchy hypotheses are tested and both are consistent with observation. Using Super-Kamiokande data only, 2-dimensional 90 % confidence allowed regions are obtained: mixing angles are constrained to $\sin^2\theta_{13} < 0.14$ and $0.37 < \sin^2\theta_{23} < 0.65$ for the normal mass hierarchy. Weaker constraints, $\sin^2\theta_{13} < 0.27$ and $0.37 < \sin^2\theta_{23} < 0.69$, are obtained for the inverted mass hierarchy case.Comment: 7 figures, 3 table

Evidence for an oscillatory signature in atmospheric neutrino oscillation

Muon neutrino disappearance probability as a function of neutrino flight length L over neutrino energy E was studied. A dip in the L/E distribution was observed in the data, as predicted from the sinusoidal flavor transition probability of neutrino oscillation. The observed L/E distribution constrained nu_mu nu_tau neutrino oscillation parameters; 1.9x10^-3 < Delta m^2 < 3.0x10^-3 eV^2 and \sin^2(2theta) > 0.90 at 90% confidence level.Comment: 5 pages, 5 figures, submitted to PR