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Hausen am Albis / Hausen (Dorf), Switzerland

Levin I.,University of Heidelberg | Naegler T.,University of Heidelberg | Heinz R.,University of Heidelberg | Osusko D.,University of Heidelberg | And 10 more authors.
Atmospheric Chemistry and Physics | Year: 2010

Emissions of sulphur hexafluoride (SF6), one of the strongest greenhouse gases on a per molecule basis, are targeted to be collectively reduced under the Kyoto Protocol. Because of its long atmospheric lifetime (estimated as 800 to 3200 years), the accumulation of SF6 in the atmosphere is a direct measure of its global emissions. Examination of our extended data set of globally distributed high-precision SF6 observations shows an increase in SF6 abundance from near zero in the 1970s to a global mean of 6.7 ppt by the end of 2008. In-depth evaluation of our long-term data records shows that the global source of SF6 decreased after 1995, most likely due to SF6 emission reductions in industrialised countries, but increased again after 1998. By subtracting those emissions reported by Annex I countries to the United Nations Framework Convention of Climatic Change (UNFCCC) from our observation-inferred SF 6 source leaves a surprisingly large gap of more than 70-80% of non-reported SF6 emissions in the last decade. This suggests a strong under-estimation of emissions in Annex I countries and underlines the urgent need for independent atmospheric verification of greenhouse gases emissions accounting. © Author(s) 2010.

Pillai D.,Max Planck Institute for Biogeochemistry | Pillai D.,University of Bremen | Gerbig C.,Max Planck Institute for Biogeochemistry | Kretschmer R.,Max Planck Institute for Biogeochemistry | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2012

We present simulations of atmospheric CO 2 concentrations provided by two modeling systems, run at high spatial resolution: the Eulerian-based Weather Research Forecasting (WRF) model and the Lagrangian-based Stochastic Time-Inverted Lagrangian Transport (STILT) model, both of which are coupled to a diagnostic biospheric model, the Vegetation Photosynthesis and Respiration Model (VPRM). The consistency of the simulations is assessed with special attention paid to the details of horizontal as well as vertical transport and mixing of CO 2 concentrations in the atmosphere. The dependence of model mismatch (Eulerian vs. Lagrangian) on models' spatial resolution is further investigated. A case study using airborne measurements during which two models showed large deviations from each other is analyzed in detail as an extreme case. Using aircraft observations and pulse release simulations, we identified differences in the representation of details in the interaction between turbulent mixing and advection through wind shear as the main cause of discrepancies between WRF and STILT transport at a spatial resolution such as 2 and 6 km. Based on observations and inter-model comparisons of atmospheric CO 2 concentrations, we show that a refinement of the parameterization of turbulent velocity variance and Lagrangian time-scale in STILT is needed to achieve a better match between the Eulerian and the Lagrangian transport at such a high spatial resolution (e.g. 2 and 6 km). Nevertheless, the inter-model differences in simulated CO 2 time series for a tall tower observatory at Ochsenkopf in Germany are about a factor of two smaller than the model-data mismatch and about a factor of three smaller than the mismatch between the current global model simulations and the data. © 2012 Author(s).

Neininger B.,MetAir AG | Neininger B.,ZHAW Zurich University of Applied Sciences | Hacker J.M.,Flinders University
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2011

This paper is an attempt to compare, and possibly combine, the capabilities and technologies available for using either small UAS or small manned aircraft, or both, for environmental research applications including geomatics. The paper is emphasising the view that instead of making one or the other platform technology (manned or unmanned) the deciding factor for specific applications in an a priori sense, it would be a better approach to evaluate each technology's suitability and merits in terms of ease of use (instrumentation integration, operational aspects, potential restrictions, safety, etc.) and also cost-efficiency. As will be shown, in some cases, this might even mean that a combination of manned and unmanned aerial platforms could be the optimum choice for a specific set of tasks. The paper introduces a number of manned and unmanned small aerial platforms and looks at their specific proven and envisaged capabilities for specific tasks. It also introduces the concept of using manned and unmanned aerial platform in tandem, maximising the usefulness of both technologies together for specific tasks. The authors' intent is to encourage a close look at all technologies available today, or in the near future, and to make that the basis for decisions about which ones are the most suitable ones for specific applications or projects. Two field campaigns in which METAIR and ARA have operated their small manned aerial platforms are re- Analysed to give an example of the considerations that should be evaluated to decide which platform technology might be the most suitable one for a specific project. One of the projects ("TIPPEX") was flown in 2008 in Northern Australia, while the other one ("MAIOLICA") had flight campaigns in 2009 and 2011 in Switzerland.

Graf A.,Julich Research Center | Schuttemeyer D.,University of Bonn | Geiss H.,Julich Research Center | Knaps A.,Julich Research Center | And 6 more authors.
Boundary-Layer Meteorology | Year: 2010

Higher-order moments, minima and maxima of turbulent temperature and water vapour mixing ratio probability density functions measured with an eddy-covariance system near the ground were related to each other and to vertical boundary-layer profiles of the same scalars obtained through airborne soundings. The dependence of kurtosis on squared skewness showed a kurtosis intercept below the Gaussian expectation, suggesting a compression of the probability density function by the presence of natural boundaries. This hypothesis was corroborated by comparing actual minima and maxima of turbulent fluctuations to estimates obtained from the first four sample moments by fitting a four-parameter beta distribution. The most sharply defined boundaries were found for the minima of temperature datasets during the day, indicating that negative temperature fluctuations at the sensor are limited by the availability of lower temperatures in the boundary layer. By comparison to vertical profiles, it could be verified that the turbulent minimum of temperature near the ground is close to the minimum of potential temperature in the boundary layer. The turbulent minimum of water vapour mixing ratio was found to be equal to the mixing ratio at a height above the minimum of the temperature profile. This height roughly agrees with the top of the non-local unstable domain according to bulk Richardson number profiles. We conclude that turbulence statistics measured near the surface cannot be solely explained by local effects, but contain information about the whole boundary layer including the entrainment zone. © 2009 Springer Science+Business Media B.V.

Pillai D.,Max Planck Institute for Biogeochemistry | Gerbig C.,Max Planck Institute for Biogeochemistry | Ahmadov R.,National Oceanic and Atmospheric Administration | Ahmadov R.,University of Colorado at Boulder | And 7 more authors.
Atmospheric Chemistry and Physics | Year: 2011

Accurate simulation of the spatial and temporal variability of tracer mixing ratios over complex terrain is challenging, but essential in order to utilize measurements made in complex orography (e.g. mountain and coastal sites) in an atmospheric inverse framework to better estimate regional fluxes of these trace gases. This study investigates the ability of high-resolution modeling tools to simulate meteorological and CO2 fields around Ochsenkopf tall tower, situated in Fichtelgebirge mountain range-Germany (1022 m a.s.l.; 50°1′48" N, 11°48′30" E). We used tower measurements made at different heights for different seasons together with the measurements from an aircraft campaign. Two tracer transport models-WRF (Eulerian based) and STILT (Lagrangian based), both with a 2 km horizontal resolution-are used together with the satellite-based biospheric model VPRM to simulate the distribution of atmospheric CO2 concentration over Ochsenkopf. The results suggest that the high-resolution models can capture diurnal, seasonal and synoptic variability of observed mixing ratios much better than coarse global models. The effects of mesoscale transports such as mountain-valley circulations and mountain-wave activities on atmospheric CO2 distributions are reproduced remarkably well in the high-resolution models. With this study, we emphasize the potential of using high-resolution models in the context of inverse modeling frameworks to utilize measurements provided from mountain or complex terrain sites. © 2011 Author(s).

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