The FLUXNET2015 dataset provides ecosystem-scale data on CO 2 , water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.

Abstract.A parameterization scheme for calculating gaseous dry deposition velocities in air-quality models is revised based on recent study results on non-stomatal uptake of O 3 and SO 2 over 5 different vegetation types. Non-stomatal resistance, which includes in-canopy aerodynamic, soil and cuticle resistances, for SO 2 and O 3 is parameterized as a function of friction velocity, relative humidity, leaf area index, and canopy wetness. Non-stomatal resistance for other chemical species is scaled to those of SO 2 and O 3 based on their chemical and physical characteristics. Stomatal resistance is calculated using a two-big-leaf stomatal resistance sub-model for all gaseous species of interest. The improvements in the present model compared to its earlier version include a newly developed non-stomatal resistance formulation, a realistic treatment of cuticle and ground resistance in winter, and the handling of seasonally-dependent input parameters. Model evaluation shows that the revised parameterization can provide more realistic deposition velocities for both O 3 and SO 2 , especially for wet canopies. Example model output shows that the parameterization provides reasonable estimates of dry deposition velocities for different gaseous species, land types and diurnal and seasonal variations. Maximum deposition velocities from model output are close to reported measurement values for different land types. The current parameterization can be easily adopted into different air-quality models that require inclusion of dry deposition processes.

Inferential models have long been used to determine pollutant dry deposition to ecosystems from measurements of air concentrations and as part of national and regional atmospheric chemistry and transport models, and yet models still suffer very large uncertainties. An inferential network of 55 sites throughout Europe for atmospheric reactive nitrogen (N_r) was established in 2007, providing ambient concentrations of gaseous NH₃, NO₂, HNO₃ and HONO and aerosol NH₄⁺ and NO₃^&minus; as part of the NitroEurope Integrated Project. <br><br> Network results providing modelled inorganic N_r dry deposition to the 55 monitoring sites are presented, using four existing dry deposition routines, revealing inter-model differences and providing ensemble average deposition estimates. Dry deposition is generally largest over forests in regions with large ambient NH₃ concentrations, exceeding 30–40 kg N ha⁻¹ yr⁻¹ over parts of the Netherlands and Belgium, while some remote forests in Scandinavia receive less than 2 kg N ha⁻¹ yr⁻¹. Turbulent N_r deposition to short vegetation ecosystems is generally smaller than to forests due to reduced turbulent exchange, but also because NH₃ inputs to fertilised, agricultural systems are limited by the presence of a substantial NH₃ source in the vegetation, leading to periods of emission as well as deposition. <br><br> Differences between models reach a factor 2–3 and are often greater than differences between monitoring sites. For soluble N_r gases such as NH₃ and HNO₃, the non-stomatal pathways are responsible for most of the annual uptake over many surfaces, especially the non-agricultural land uses, but parameterisations of the sink strength vary considerably among models. For aerosol NH₄⁺ and NO₃^&minus; discrepancies between theoretical models and field flux measurements lead to much uncertainty in dry deposition rates for fine particles (0.1–0.5 μm). The validation of inferential models at the ecosystem scale is best achieved by comparison with direct long-term micrometeorological N_r flux measurements, but too few such datasets are available, especially for HNO₃ and aerosol NH₄⁺ and NO₃^&minus;

Abstract. A size-resolved particle dry deposition scheme is developed for inclusion in large-scale air quality and climate models where the size distribution and fate of atmospheric aerosols is of concern. The "resistance" structure is similar to what is proposed by Zhang et al. (2001), while a new "surface" deposition velocity (or surface resistance) is derived by simplification of a one-dimensional aerosol transport model (Petroff et al., 2008b(Petroff et al., , 2009). Compared to Zhang et al.'s model, the present model accounts for the leaf size, shape and area index as well as the height of the vegetation canopy. Consequently, it is more sensitive to the change of land covers, particularly in the accumulation mode (0.1-1 micron). A drift velocity is included to account for the phoretic effects related to temperature and humidity gradients close to liquid and solid water surfaces. An extended comparison of this model with experimental evidence is performed over typical land covers such as bare ground, grass, coniferous forest, liquid and solid water surfaces and highlights its adequate prediction. The predictions of the present model differ from Zhang et al.'s model in the fine mode, where the latter tends to over-estimate in a significant way the particle deposition, as measured by various investigators or predicted by the present model. The present development is thought to be useful to modellers of the atmospheric aerosol who need an adequate parameterization of aerosol dry removal to the earth surface, described here by 26 land covers. An open source code is available in Fortran90.

[1] The air-surface exchange of atmospheric ammonia (NH 3 ) and measurements of the canopy and stomatal compensation points (c cp and c st , respectively) and the stomatal and soil emission potentials (G st and G g , respectively) are reviewed. A database of these values has been developed, to be used for the development of input parameters and for model evaluation. The compensation points are dependent on canopy type, nitrogen (N) status, temperature, growth stage, and meteorological conditions. Canopies that receive high atmospheric nitrogen input generally have high c cp values. c cp values also tend to be higher over intensively managed vegetated surfaces than semi-natural vegetation, due to the higher nitrogen content in these surfaces. Increased nitrogen concentrations from fertilization and cutting practices have been observed to increase the compensation points and therefore the emission from these canopies. The decomposition of litter leaves has been found to play a dominant role and significantly increase the values of c cp over agricultural vegetation and fertilized grasslands. By modifying an existing big-leaf dry deposition model to allow NH 3 emission from leaf stomata and soil surfaces, a bi-directional air-surface exchange model has been developed for applications in regional-scale air-quality models. The model predicts c cp values that vary with canopy type, nitrogen content, and meteorological conditions. c cp values predicted by the model are around 1-2 mg m −3 over forest canopies and 4-10 mg m −3 over grasslands and agricultural canopies during a typical summer daytime; c cp values are ∼10 and ∼3 times lower over forests and agricultural lands, respectively, in nighttime and/or winter conditions. These results are similar to the range of measured values. The new bi-directional air-surface exchange model will reduce the dry deposition fluxes by 20-100 ng m −2 s −1 compared to the original dry deposition model over low-N forests and agricultural lands during typical summer daytime conditions, which can be the difference between whether deposition or emission occurs. For example, this new model produces emissions fluxes of 0-90 ng m −2 s −1 over croplands when the atmospheric NH 3 concentrations are below 10 mg m −3 .

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Daily 24-hour PM 2.5 samples were collected continuously from January 1 to December 31, 2010. Elemental concentrations from Al to Pb were obtained using particle induced X-ray emission (PIXE) method. This was the first full year continuous daily PM 2.5 elemental composition dataset in Beijing. Source apportionment analysis was conducted on this dataset using the positive matrix factorization method. Seven sources and their contributions to the total PM 2.5 mass were identified and quantified. These include secondary sulphur-13.8 μg/m 3 ) compared to those in the spring and summer (9.6 and 8.0 μg/m 3 , respectively). Secondary sulphur contributed the most in the summer while vehicle exhaust and metal processing sources did not show any clear seasonal pattern. The different seasonal highs and lows from different sources compensated each other. This explains the very small seasonal variations (< 20%) in the total PM 2.5 .

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