A model-based evaluation of Marine Protected Areas: the example of eastern Baltic cod (Gadus morhua callarias L.)     

Kraus  Gerd; Pelletier  Dominique; Dubreuil  Julien; Mollmann  Christian; Hinrichsen  Hans-Harald; Bastardie  Francois; Vermard  Youen; Mahevas  Stephanie 《ICES Journal of Marine Science》2009,66(1):109-121

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The role of radiation in an inversion-capped planetary boundary layer     

Eberhard Schaller  Helmut Kraus 《Boundary-Layer Meteorology》1981,20(4):485-495

In an inversion-capped planetary boundary layer (PBL), the structure of the turbulent fluxes as well as the height of the inversion are determined by the interaction of turbulent mixing in the PBL, large-scale subsidence above the PBL and radiational cooling. Here the sensitivity of the inversion height and of the turbulent fluxes due to radiational processes is investigated with the aid of a three-layered model for a well mixed PBL. For an example of the Trade-Wind region, the inversion height (i.e., the difference between surface pressure and pressure at the inversion level) varies between 46 and 257 mb and the surface flux of moist static energy between 417 and 99 W m^-2, if the (mean) radiative net flux divergence for both the inversion and the well-mixed layer is changed over a reasonable range of values. None of the parameterization schemes existing in the literature is able to describe these radiational effects in an appropriate way. This is due to the fact that these parameterizations are either not or not flexibly enough linked to the thermodynamical model parameter. Therefore the demand for an adequate parameterization of the radiational influence in a well-mixed PBL under a subsidence inversion is obvious.  相似文献   

Steady-state characteristics of inversions capping a well-mixed planetary boundary layer     

H. Kraus  E. Schaller 《Boundary-Layer Meteorology》1978,14(1):83-104

The type of inversion discussed in this paper is essentially defined by subsidence, mixing due to thermally generated turbulent energy and a radiative flux difference at the inversion. A concept similar to that of Lilly (1968) is applied, assuming a well-mixed layer below the inversion and including advective and radiative processes.The characteristics of the inversion and of the whole PBL (e.g., height of inversion, height of cloud base, strength of inversion, flux-profiles) are investigated for their dependence on external parameters such as horizontal wind field divergence, advection, surface temperature excess, wind speed and surface temperature. This is done for steady-state conditions and gives considerable insight into the processes maintaining the type of inversion under consideration.A second goal is to present typical inversion structures, which can be found in certain climatic regions. The profiles of the state parameters and the energy-fluxes for the Trade-Wind region, the cold water area off the west-coast of California, the Norwegian Sea and the Arctic Ocean differ considerably.  相似文献   

Field Measurements of Atmospheric Photolysis Frequencies for O3, NO2, HCHO, CH3CHO, H2O2, and HONO by UV Spectroradiometry     

A. Kraus  A. Hofzumahaus 《Journal of Atmospheric Chemistry》1998,31(1-2):161-180

A calibrated spectroradiometer was used for the measurement of spectra of the absolute actinic flux F during the POPCORN field campaign in Pennewitt (53.8° N, 11.7° E, sea level) in August 1994. The obtained set of actinic flux spectra was used to determine the photolysis frequencies J(O1D), J(NO2), J(HCHO), J(H2O2), J(HONO), and J(CH3CHO), using molecular photodissociation data from literature. The accuracy of the actinic flux measurement was about ±5%. The accuracy of the photolysis frequency determination is limited by the uncertainties of the molecular absorption cross section and quantum yield data. A good agreement within the experimental uncertainties was found in comparison with measurements of J(O1D) and J(NO2) by filterradiometer which were calibrated absolutely against chemical actinometer. A comparison of this work's photolysis frequency measurements at 40° solar zenith angle with respective measured and modeled data from the literature also shows good agreement for most of the processes considered in this work. However, in the case of J(NO2) data reported in the literature as a function of solar zenith angle differences up to a factor of 1.6 with respect to this work's J(NO2) data are observed. Since this is far beyond the estimated experimental uncertainties, other atmospheric variables, such as aerosols, seem to affect J(NO2) to an extent that is underestimated by now and make indirect comparisons of J(NO2) measurements difficult.  相似文献   

Meteorological Aspects, Ozone, and Solar Radiation Measurements During POPCORN 1994     

Theo Brauers  Hans-Peter Dorn  Helmut Koch  Annette B. Kraus  Christian Plass-Dülmer 《Journal of Atmospheric Chemistry》1998,31(1-2):33-52

Meteorological data, ozone mixing ratios, and photolysis frequencies for the period August 2 to August 24, 1994, are presented and discussed in support of the field campaign POPCORN (Photochemistry of Plant Emitted Compounds and OH Radicals in Northeastern Germany). Measurements of temperature, ozone, and wind speed at different heights are used to evaluate micro-meteorological parameters. The observations provide information about local influences on the air mass composition. The analysis of radio sonde data of nearby stations provides the height of the planetary boundary layer.  相似文献   

Evolutionary relationship between the γ-ray flares and millimeter wave outbursts in PKS 0528+134     

Shan-jie Qian  Xi-zhen Zhang  S. Britzen  A. Witzel  T. Krichbaum  A. Kraus  E. Valtaoja  H.D. Aller 《Chinese Astronomy and Astrophysics》1998,22(4):409-418

During the period of 1991–1993 two strong high energy γ-ray flares were observed by the Compton Gamma Ray Observatory in the flat spectrum radio source PKS 0528+134. They were associated with strong mm-radio outbursts with a few months time-delays. In this paper the spectral energy distributions (SED) of the radiations in the γ-hand X-ray and the IR-optical bands are analysed. It is shown that the high energy γ-ray radiation may be due to the inverse Compton scattering of the ambient UV and soft X-ray photons by the relativistic electrons in the jet. Basing on the comparison between the properties of the synchrotron radiation of the γ-ray source and the spectral evolution of the mm-radio outbursts, the evolutional relationship between the γ-ray emitting blobs and the mm-radio emitting blobs is discussed.  相似文献   

Frontal substructures within the planetary boundary layer   总被引：2，自引：0，他引：2  

Andreas Becker  Helmut Kraus  Cäcilia M. Ewenz 《Boundary-Layer Meteorology》1996,78(1-2):165-190

A two-dimensional mesoscale model, extended by a TKE closure for the subgrid-scale terms and coupled with a soil model, is used to investigate the role of the Planetary Boundary Layer (PBL) for the development and the substructures of two different types of cold fronts. The effects of turbulent friction, large-scale (geostrophic) forcing and the diurnal variation of the terms of the surface energy balance (SEB) equation on the frontal development are studied by 10 different model runs. The ageostrophic cross-frontal circulation in the lowest two kilometres of a cold front results from friction as well as from large-scale forcing. The first one dominates the PBL processes and causes a special boundary-layer structure, which becomes apparent through the existence of seven characteristic zones defined for the x-z cross sections of potential temperature. The arrangement of these characteristic zones depends on the sense of rotation of the frictionally induced part of the ageostrophic circulation and hence on the direction of the along-front jet within the boundary layer. The daytime increase of the terms of the SEB equation for a midlatitude midsummer case leads to a strong enhancement of the frictionally induced cross-frontal circulation. The arrangement of the seven characteristic zones, however, is approximately conserved.  相似文献   

Observations of the limb effect in potassium λ7699     

J. C. Lopresto  Pauline M. Kraus  A. K. Pierce 《Solar physics》1994,149(2):243-247

Center-to-limb observations of the Ki 7699 line made on 30 days over a five-year period using the McMath-Pierce Solar Telescope at Kitt Peak are presented. Both a relative and absolute limb effect have been derived from the data. Our determination of the limb effect in Ki 7699 shows a linear increase to the limb amounting to about 40 m s^–1.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.  相似文献   

Diurnal variability in riverine dissolved organic matter composition determined by in situ optical measurement in the San Joaquin River (California,USA)   总被引：1，自引：0，他引：1  

Robert G. M. Spencer  Brian A. Pellerin  Brian A. Bergamaschi  Bryan D. Downing  Tamara E. C. Kraus  David R. Smart  Randy A. Dahlgren  Peter J. Hernes 《水文研究》2007,21(23):3181-3189

Dissolved organic matter (DOM) concentration and composition in riverine and stream systems are known to vary with hydrological and productivity cycles over the annual and interannual time scales. Rivers are commonly perceived as homogeneous with respect to DOM concentration and composition, particularly under steady flow conditions over short time periods. However, few studies have evaluated the impact of short term variability (<1 day) on DOM dynamics. This study examined whether diurnal processes measurably altered DOM concentration and composition in the hypereutrophic San Joaquin River (California) during a relatively quiescent period. We evaluated the efficacy of using optical in situ measurements to reveal changes in DOM which may not be evident from bulk dissolved organic carbon (DOC) measurement alone. The in situ optical measurements described in this study clearly showed for the first time diurnal variations in DOM measurements, which have previously been related to both composition and concentration, even though diurnal changes were not well reflected in bulk DOC concentrations. An apparent asynchronous trend of DOM absorbance and chlorophyll‐a in comparison to chromophoric dissolved organic matter (CDOM) fluorescence and spectral slope S_290–350 suggests that no one specific CDOM spectrophotometric measurement explains absolutely DOM diurnal variation in this system; the measurement of multiple optical parameters is therefore recommended. The observed diurnal changes in DOM composition, measured by in situ optical instrumentation likely reflect both photochemical and biologically‐mediated processes. The results of this study highlight that short‐term variability in DOM composition may complicate trends for studies aiming to distinguish different DOM sources in riverine systems and emphasizes the importance of sampling specific study sites to be compared at the same time of day. The utilization of in situ optical technology allows short‐term variability in DOM dynamics to be monitored and serves to increase our understanding of its processing and fundamental role in the aquatic environment. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Trans-Atlantic Geopotentials During the July 2000 Solar Event and Geomagnetic Storm     

Lanzerotti  L.J.  Medford  L.V.  Maclennan  C.G.  Kraus  J.S.  Kappenman  J.  Radasky  W. 《Solar physics》2001,204(1-2):351-359

The large solar activity in mid-July 2000 produced a severe geomagnetic storm at Earth during the last half of 15 July universal time. The enhancements and changes in the ionosphere electrical current systems caused large geopotentials to be induced over oceanic distances. Across the northern Atlantic, from New Jersey to near the French coast, a geopotential as large as 0.05 V km⁻¹ (a peak-to-peak voltage of about 300 V) was measured during the geomagnetic storm. While large, this was not among the four largest such geopotentials that have been recorded in the last 60 years across AT&T telecommunications cable routes, ocean and continental. The geomagnetic and geopotential data that were measured during the storm event are presented and discussed.  相似文献