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Miller-Schulze J.P.,Wisconsin State Laboratory of Hygiene | Miller-Schulze J.P.,University of Wisconsin - Madison | Shafer M.M.,Wisconsin State Laboratory of Hygiene | Shafer M.M.,University of Wisconsin - Madison | And 10 more authors.
Atmospheric Environment | Year: 2011

Central Asia is a relatively understudied region of the world in terms of characterizing ambient particulate matter (PM) and quantifying source impacts of PM at receptor locations, although it is speculated to have an important role as a source region for long-range transport of PM to Eastern Asia, the Pacific Ocean, and the Western United States. PM is of significant interest not only because of its adverse effect on public health but also due to its more recently realized role in climate change. To investigate the sources and characteristics of PM in the region, a series of PM2.5 and PM10 samples were collected on an every-other-day basis at two sites (termed " Bishkek" and " Teploklyuchenka" ) in the Central Asian nation of the Kyrgyz Republic (also known as Kyrgyzstan) for a full year from July 2008 to July 2009. These samples were analyzed using standard methods for mass, organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-insoluble organic carbon by difference (OC minus WSOC) and a variety of molecular marker chemical species to be used in a chemical mass balance (CMB) model to apportion the sources of OC. These analyses indicate that approximately 19 ± 6.4% of the PM2.5 mass at both sites throughout the year consists of OC. The carbonaceous component of PM2.5 is dominated by OC, with OC/Total Carbon (TC) ratios being around 0.8 in the winter to almost 0.95 in the summer months. The CMB analysis indicated that mobile sources, i.e., gasoline and diesel engine exhaust, biomass combustion, and biogenic secondary organic aerosol (SOA) formation from isoprene and α-pinene precursors in the summer months were the dominant sources of OC. A strong positive correlation was observed between non-biomass burning WSOC and the un-apportioned OC from the CMB analysis, indicating that some of this un-apportioned OC is WSOC and likely the result of SOA-forming atmospheric processes that were not estimated by the CMB analysis performed. In addition, a comparison of the predominant contributors to OC between the two sites indicates that biomass combustion is a stronger relative source of OC at the Teploklyuchenka site, particularly in the winter, while contributions of isoprene- and α-pinene-derived SOA to the measured OC was relatively similar between the sites. © 2011 Elsevier Ltd. Source

Holzapfel F.,German Aerospace Center | Holzapfel F.,Institute of Atmospheric Physics
Journal of Aircraft | Year: 2014

This study investigates the impact of meteorological parameters (crosswind, headwind, wind shear, thermal stratification, turbulent kinetic energy, dissipation rate, and density) and aircraft parameters (position, heading, speed, weight, span, and spanwise load factor) on wake-vortex behavior. Typical measurement uncertainties of these parameters, on one hand, and the range in which they typically reside, on the other hand, are mapped on variations of lateral and vertical position and lifetime of the wake vortices. For this mapping process, the deterministic two-phase wake-vortex model is employed, complemented by some simple considerations, dimensional analysis, and sources from literature. Three scenarios comprising cruise conditions, flight within the atmospheric boundary layer, and ground proximity are considered. From these investigations, the following ranking of the impact parameters has been deduced: wind, thermal stratification, turbulence, position, mass, and spanwise load factor. The relevance of the remaining parameters appears small. Copyright © 2014 by Indian Institute of Space Science and Technology, Thiruvananthapuram, India. Published by the American Institute of Aeronautics and Astronautics, Inc. Source

Fischer L.,Ludwig Maximilians University of Munich | Craig G.C.,Ludwig Maximilians University of Munich | Kiemle C.,Institute of Atmospheric Physics
Journal of Geophysical Research: Atmospheres | Year: 2013

Analysis is presented of airborne lidar measurements of water vapor, covering a height range from 1.5 to 10.4 km, from three field campaigns (midlatitude summer, polar winter, and subtropical summer). The lidar instrument provides two-dimensional cross sections of absolute humidity, with high accuracy (errors less than 5-7%) and high vertical (∼ 200 m) and horizontal (∼ 2 km) resolution. Structure functions, i.e., statistical moments up to the fifth-order of absolute increments over a range of scales, are investigated, and power law scaling or statistical-scale invariance was found over horizontal distances from 5 to 100 km. The scaling exponents are found to take different values, depending on whether or not the observations were taken in an air mass where convective clouds were present. The exponent of the first-order structure function in nonconvective regions, H=0.63±0.10, is large indicating a smooth series with long-range correlations, in contrast to the lower value H=0.35±0.11 found in convective air masses. Correspondingly, the moisture field in the convective regime was found to be more intermittent than for the nonconvective regime, i.e., water vapor structures in convectively influenced air mass show more jump discontinuities, which could be explained by the moistening and drying effects of updrafts and downdrafts in convective air mass. Within each regime (convective or nonconvective), the values appear to be universal, with no significant dependence on the season, latitude, or height where the observations were made. Furthermore, some evidence is found that vertical correlation lengths are longer in convective air masses. Key Points Mesoscale water vapor variability including the subgrid scale is characterized Scaling exponents in convective airmass are lower than in non-convective Correlation length in convective airmass is longer than in non-convective ©2013. American Geophysical Union. All Rights Reserved. Source

Gassmann A.,Institute of Atmospheric Physics
Quarterly Journal of the Royal Meteorological Society | Year: 2015

Numerical models of the atmosphere should fulfil fundamental physical laws. The second law of thermodynamics is associated with positive local entropy production and dissipation of available energy. In order to guarantee this positivity in numerical simulations, subgrid-scale turbulent fluxes of heat, water vapour and momentum are required to depend on numerically resolved gradients in a unique way. The task of parametrization remains to deliver phenomenological coefficients. Inspecting commonly used parametrizations for subgrid fluxes, we find that some of them obey the second law of thermodynamics and some do not. The conforming approaches are Smagorinsky momentum diffusion, phase changes and sedimentation fluxes for hydrometeors. Conventional turbulent heat-flux parametrizations do not conform with the second law. A new water-vapour flux formulation is derived from the requirement of locally positive entropy production. The conventional and new water-vapour fluxes are compared using high-resolution radiosonde data. Conventional water-vapour fluxes are wrong by up to 10% and exhibit a negative bias. Two numerical tests (the Boulder windstorm test case and a convective boundary-layer experiment) are performed with the Icosahedral Nonhydrostatic model at the Institute for Atmospheric Physics (ICON-IAP). The experiments compare conventional and entropy-consistent heat-flux parametrizations. Both test cases indicate that negative thermal dissipation can occur for the conventional heat flux. Obviously, the additional energy made available by this negative dissipation to the resolved turbulence is later on dissipated by friction, so that the total dissipation is again comparable, at least for the boundary-layer experiment. © 2014 Royal Meteorological Society. Source

Offermann D.,University of Wuppertal | Hoffmann P.,Institute of Atmospheric Physics | Knieling P.,University of Wuppertal | Koppmann R.,University of Wuppertal | And 3 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

Mesospheric and stratospheric temperatures and winds from several stations in Germany are analyzed for long-term trends in 1988-2008. Emphasis is on upper mesosphere (87 km) hydroxyl (OH) temperatures at Wuppertal (51°N, 7°E) that agree favorably with satellite-borne observations from Sounding of the Atmosphere Using Broadband Emission Radiometry and a twin OH instrument at Hohenpeienberg (48°N, 11°E) that is operational since 2003. The two twin stations yield a combined data set with 80% time coverage suitable for high time resolution analyses. Annual mean temperatures at Wuppertal show a long-term trend of -0.23 K/yr and a solar flux sensitivity of 0.035 K/solar flux unit. Trend analysis of monthly mean temperatures yields substantial variations from one month to another, between 0 and -0.6 K/yr, hence questioning the value of seasonal mean trends. The OH temperatures have a well-known characteristic form of seasonal variation. This form changes during the 21 years of observation. The changes are compared to modifications of the summer length in the stratosphere and are interpreted as dynamics/circulation changes extending to the uppermost parts of the middle atmosphere. Copyright 2010 by the American Geophysical Union. Source

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