Eberhard Schaller

Boundary layer structure and photochemical pollution in the Harz Mountains : An observational study

Results from a field campaign that has been performed in summer 1993 to study photochemical pollution in the Harz Mountains, Germany, are presented. During a five-day, fair-weather period, a steady increase of the daily maximum ozone concentration up to values around 100 ppb was observed in the Harz region. The results of ozone measurements at two surface stations (404 m a.s.l. and 1142 m a.s.l., respectively) are discussed with respect to both the transport and dispersion conditions during the period and the local structure of the atmospheric boundary layer. Remarkable similarities in the time series of the ozone mixing ratio at the two places have been found which indicate some kind of quasi-homogeneity even over complex terrain. The trace gas concentrations at the top of Mt. Brocken, the highest summit of the Harz Mountains, are shown to be strongly influenced by vertical transports due to convection (at daytime) and subsidence of inversion layers (at nighttime).

Aircraft measurement of pollutant fluxes across the borders of eastern Germany

We performed a research flight along the western and eastern border of eastern Germany to estimate the transboundary flux of pollution gases during a synoptic weather situation with westerly to southwesterly winds. A dolphin flight pattern was applied to sample the boundary layer as representatively as possible while screening the vertical structure of the lower troposphore. Transboundary flux intensities were calculated using concentrations and wind vectors as measured by the aircraft. A detailed error analysis was performed to estimate two types of uncertainties in the transboundary flux measurement. The error originating from inaccuracies in meteorological and chemical measurements was estimated to be in the range 15–35% (one standard deviation). The error originating from the unrepresentativeness of the data collected on the flight path is estimated to be smaller by factors between 2 and 3. Transboundary fluxes at the eastern side of eastern Germany were different from those at the western side at a high level of confidence (>95%). Transboundary fluxes were greater on the eastern side by a factor of 12 for SO2 and by a factor of 2.9 for NOy. For SO2, the transboundary fluxes in the Ekman layer (EL) and inversion layer (IL) were greater than those of lower free troposphere (LFT) on both sides, whereas for NOy and O3 higher LFT wind speeds compensated higher EL and IL mixing ratios. A compilation of all available data on pollutant gas export from eastern Germany reveals a very heterogeneous data set. Computed average fluxes, however, show good agreement with estimates of pollutant gas emissions from eastern Germany, based on energy consumption.

Characterization of ozone plumes in eastern Germany

During a photosmog period in summer 1993, several ozone plumes (enrichment of O3 of 10–45 ppb over levels of surrounding air masses) were observed in the southern part of eastern Germany. Analyses of the plumes for other species reveal that SO2, NOy, CO, and photochemically formed CH2O were enriched synchronously with O3. The measured enhancement factors SO2/CO and NOy/CO agree well with emission factors of local emission inquiries. The O3 production potential in the plumes must have originated from emissions from furnaces burning sulfur rich lignite coal under non-optimum conditions such as old power plants, industrial plants, and domestic water heating systems. The co-emission of VOCs with SO2 lead to the formation of O3 and CH2O. Most of the plumes seem to be less than one day old.

Mean flow generation by Görtler vortices in a rotating annulus with librating side walls

Time periodic variation of the rotation rate of an annulus induces in supercritical regime an unstable Stokes boundary layer over the cylinder side walls, generating Gortler vortices in a portion of a libration cycle as a discrete event. Numerical results show that these vortices propagate into the fluid bulk and generate an azimuthal mean flow. Direct numerical simulations of the fluid flow in an annular container with librating outer (inner) cylinder side wall and Reynolds-averaged Navier–Stokes (RANS) equations as diagnostic equations are used to investigate generation mechanism of the retrograde (prograde) azimuthal mean flow in the bulk. First, we explain, phenomenologically, how absolute angular momentum of the bulk flow is mixed and changed due to the propagation of the Gortler vortices, causing a new vortex of basin size. Then we investigate the RANS equations for intermediate time scale of the development of the Gortler vortices and for long time scale of the order of several libration periods. The former exhibits sign selection of the azimuthal mean flow. Investigating the latter, we predict that the azimuthal mean flow is proportional to the libration amplitude squared and to the inverse square root of the Ekman number and libration frequency and then confirms this using the numerical data. Additionally, presence of an upscale cascade of energy is shown, using the kinetic energy budget of fluctuating flow.

High Resolution Climate Change Simulation for Central Europe

Two regional climate simulations are performed with a high-resolution limited area model for Central Europe, representing present-day climate conditions and a future climate change scenario according to a doubled global CO 2-concentration. Results of a global climate change simulation are used to initialize the regional model and to drive the simulations via time-dependent boundary values. The regional simulations show considerable changes in temperature and precipitation with noticeable geographical and seasonal modifications. For Germany, a significant warming of up to 4K emerges but the simulated tendency of decreasing summer rainfall cannot be approved as significant.

Issues and Opportunities for Implementation of VSS in China

This chapter aims to discuss the current situation and the implementation of VSS in China where it is still not widely recognised. China is one of the fastest developing countries in the world and plays a very important role in the worlds’ economy. However, along with its rapid development, a series of consequences, both economic and environmental, have drawn massive attention from the public and media. Chinese industries have an urgent need of tools to enhance their reputation internationally. Since the mid-1990s when voluntary sustainability standards (VSS) were first introduced in mainland China, many companies especially SMEs (small and medium enterprises) were reluctant to engage with VSS. It is therefore important to study the reasons for these setbacks and possible solutions while taking into account the political background, the specific conditions and the institutional realities in China.