Operational mapping of atmospheric nitrogen deposition to the Baltic Sea

International audienceA new model system for mapping and forecasting nitrogen deposition to the Baltic Sea has been developed. The system is based on the Lagrangian variable scale transport-chemistry model ACDEP (Atmospheric Chemistry and Deposition model), and aims at delivering deposition estimates to be used as input to marine ecosystem models. The system is tested by comparison of model results to measurements from monitoring stations around the Baltic Sea. The comparison shows that observed annual mean ambient air concentrations and wet depositions are well reproduced by the model. Diurnal mean concentrations of NHx (sum of NH3 and NH4+) and NO2 are fairly well reproduced, whereas concentrations of total nitrate (sum of HNO3 and NO3-) are somewhat overestimated. Wet depositions of nitrate and ammonia are fairly well described for annual mean values, whereas the discrepancy is high for the monthly mean values and the wet depositions are rather poorly described concerning the diurnal mean values. The model calculations show that the annual atmospheric nitrogen deposition has a pronounced south--north gradient with depositions in the range about 1.0 T N km-2 in the south and 0.2 T N km-2 in the north. The results show that in 1999 the maximum diurnal mean deposition to the Danish waters appeared during the summer in the algae growth season. For the northern parts of the Baltic the highest depositions were distributed over most of the year. Total deposition to the Baltic Sea was for the year 1999 estimated to 318 kT N for an area of 464 406 km2 equivalent to an average deposition of 684 kg N/km2

Growth in densely populated Asia: implications for primary product exporters

Economic growth and integration in Asia is rapidly increasing the global economic importance of the region. To the extent that this growth continues and is strongest in natural resource-poor Asian economies, it will add to global demand for imports of primary products, to the benefit of (especially nearby) resource-abundant countries. How will global production, consumption and trade patterns change by 2030 in the course of such economic developments and structural changes? We address this question using the GTAP model and Version 8.1 of the 2007 GTAP database, together with supplementary data from a range of sources, to support projections of the global economy from 2007 to 2030 under various scenarios. Factor endowments and real gross domestic product are assumed to grow at exogenous rates, and trade-related policies are kept unchanged to generate a core baseline, which is compared with an alternative slower growth scenario. We also consider the impact of several policy changes aimed at increasing China's agricultural self-sufficiency relative to the 2030 baseline. Policy implications for countries of the Asia-Pacific region are drawn out in the final section

Experimental Characterization of Space Charge in IZIP Detectors

Interleaved ionization electrode geometries offer the possibility of efficient rejection of near-surface events. The CDMS collaboration has implemented this interleaved approach for the charge and phonon readout for our germanium detectors. During a recent engineering run with negligible ambient radiation, the detectors were found to lose ionization stability more quickly than expected. This paper summarizes studies done in order to determine the underlying cause of the instability, as well as possible running modes that maintain stability without unacceptable loss of livetime. Additionally, first results are shown for the new version IZIP mask which attempts to improve the overall stability of the detectors.United States. Dept. of Energy (Grant DE-AC02-76SF00515)National Science Foundation (U.S.) (Awards 0705052, 0902182, 1004714, and 0802575

Electron-electron interaction at decreasing kFlk_Fl

The contribution of the electron-electron interaction to conductivity is analyzed step by step in gated GaAs/InGaAs/GaAs heterostructures with different starting disorder. We demonstrate that the diffusion theory works down to $k_F l\simeq 1.5-2$, where $k_F$ is the Fermi quasimomentum, $l$ is the mean free paths. It is shown that the e-e interaction gives smaller contribution to the conductivity than the interference independent of the starting disorder and its role rapidly decreases with $k_Fl$ decrease.Comment: 5 pages, 6 figure

Luttinger liquid behavior in multi-wall carbon nanotubes

The low-energy theory for multi-wall carbon nanotubes including the long-ranged Coulomb interactions, internal screening effects, and single-electron hopping between graphite shells is derived and analyzed by bosonization methods. Characteristic Luttinger liquid power laws are found for the tunneling density of states, with exponents approaching their Fermi liquid value only very slowly as the number of conducting shells increases. With minor modifications, the same conclusions apply to transport in ropes of single-wall nanotubes.Comment: 4 pages Revte

Spatial and temporal variations in ammonia emissions – a freely accessible model code for Europe

Deriving a parameterisation of ammonia emissions for use in chemistry-transport models (CTMs) is a complex problem as the emission varies locally as a result of local climate and local agricultural management. In current CTMs such factors are generally not taken into account. This paper demonstrates how local climate and local management can be accounted for in CTMs by applying a modular approach for deriving data as input to a dynamic ammonia emission model for Europe. Default data are obtained from information in the RAINS system, and it is demonstrated how this dynamic emission model based on these input data improves the NH<sub>3</sub> calculations in a CTM model when the results are compared with calculations obtained by traditional methods in emission handling. It is also shown how input data can be modified over a specific target region resulting in even further improvement in performance over this domain. The model code and the obtained default values for the modelling experiments are available as supplementary information to this article for use by the modelling community on similar terms as the EMEP CTM model: the GPL licencse v3

Electron-Phonon Scattering in Metallic Single-Walled Carbon Nanotubes

Electron scattering rates in metallic single-walled carbon nanotubes are studied using an atomic force microscope as an electrical probe. From the scaling of the resistance of the same nanotube with length in the low and high bias regimes, the mean free paths for both regimes are inferred. The observed scattering rates are consistent with calculations for acoustic phonon scattering at low biases and zone boundary/optical phonon scattering at high biases.Comment: 4 pages, 5 figure

Micro-scale Modelling of the Urban Wind Speed for Air Pollution Applications

Modelling wind speeds in urban areas have many applications e.g. in relation to assessment of wind energy, modelling air pollution, and building design and engineering. Models for extrapolating the urban wind speed exist, but little attention has been paid to the influence of the upwind terrain and the foundations for the extrapolation schemes. To analyse the influence of the upwind terrain and the foundations for the extrapolation of the urban wind speed, measurements from six urban and non-urban stations were explored, and a model for the urban wind speed with and without upwind influence was developed and validated. The agreement between the wind directions at the stations is found to be good, and the influence of atmospheric stability, horizontal temperature gradients, land-sea breeze, temperature, global radiation and Monin-Obukhov Length is found to be small, although future work should explore if this is valid for other urban areas. Moreover, the model is found to perform reasonably well, but the upwind influence is overestimated. Areas of model improvement are thus identified. The upwind terrain thus influences the modelling of the urban wind speed to a large extent, and the fundamental assumptions for the extrapolation scheme are fulfilled for this specific case