Registrierungen der langwelligen Gegenstrahlung in Frankfurt     

Dipl. Meteor. Ernst Kreitz 《Pure and Applied Geophysics》1954,28(1):292-300

Zusammenfassung Es wird über Registrierungen der langwelligen Gegenstrahlung berichtet, die von März bis Oktober 1953 tags und nachts in Frankfurt durchgeführt wurden. Bei der Bearbeitung des Materials wurden erstmalig die gemessenen stündlichen Summenwerte und keine Einzelwerte zugrundegelegt, wodurch die hier gefundenen Beziehungen für Berechnungen der Gegenstrahlung grössere Allgemeingültigkeit haben. Die langwellige Strahlung ist fast doppelt so gross wie die kurzwellige Sonnen- und Himmelsstrahlung auf die Horizontalfläche. Die gemessenen Werte der Gegenstrahlung stimmen im grossen Mittel mit den nach derFeussner-schen Formel berechneten gut überein, doch sind die einzelnen Abweichungen davon sehr gross. Wie schon von anderen Autoren wurde auch hier festgestellt, dass die Gegenstrahlung mit zunehmender Bewölkung quadratisch zunimmt, allein bei tiefer Bewölkung ist tagsüber ein annähernd linearer Zusammenhang vorhanden. Negative Effektivstrahlung ist weit häufiger, als bisher angenommen, jedoch kommt sie fast nur in den Vormittagsstunden vor. Bei dichter niedriger Bewölkung ist der Wärmestrom nach Sonnenaufgang daher von oben nach unten gerichtet. Die Gegenstrahlung lässt sich hinreichend gut berechnen, wenn man dieFeussnersche Formel, Mittelwerte der Temperatur, des Dampfdruckes, der Bewölkungsstärke und die hier gefundene Bewölkungs-Beziehung zugrundelegt.

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Summary From March to Oct. 1953, the atmospheric long wave radiation has been recorded in Frankfurt during day and night time. For evaluating the records, no instantaneous values were taken, but the hourly sums, so that the relations found can more generally be used for computations. The atmospheric long wave radiation is almoust twice as strong as the short wave radiation from sun and sky on a horizontal plane. The mean measured values of the atmospheric long wave radiation coincide well with theFeussners formula. However, the deviations of the single values are very large. Confirming the results of other authors, it has been found that the atmospheric long wave radiation increases with the second power of the cloudiness, only with low clouds in daytime the increase is approximatly linear. Negative values of the effektive radiation occurs more frequently than expected uptil to day, but only in the time before noon. So with a dense low cloud cover the flow of heat after sunrise is directed downward. The atmospheric long wave radiation may satisfactorily be computed, ifFeussners formula, mean values of temperature, vapour pressure, cloudiness, and the mentioned cloudiness relation are taken.

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Ein einfaches Gerät zur Registrierung der langwelligen Gegenstrahlung auch bei Tage     

Dipl. Ernst Kreitz 《Pure and Applied Geophysics》1953,26(1):183-190

Zusammenfassung Das beschriebene Registrierpyrgeometer hat sich als Ergebnis längerer Versuche zum Bau eines Strablungsmessinstrumentes für die langwellige Gegenstrahlung in der Praxis bewährt. Als Strahlungsempfänger dient eine mit Magnesiumoxyd geweisste Thermosäule, um die tagsüber vorhandene kurzwellige Strahlung auszuschalten. Als Windschutz wird eine Filterplatte aus KRS 5 verwendet, welche zur besseren Erfüllung des cos-Gesetzes die Form einer Zerstreuungslinse besitzt. Die Registrierung erfolgt fortlaufend seit Anfang März dieses Jahres mittels Punktschreibers bei jedem Wetter sowohl bei Tage als auch bei Nacht und wird über einen längeren Zeitraum weitergeführt werden. Die Apparatur ist absolut geeicht und an einigen Registrierbeispielen werden die Vor- und Nachteile derselben beschrieben.

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Summary On the basis of experimental investigations a recording pyrgeometer for measuring the long wave radiation of the atmosphere has been built which is in successful practical use since some months. The radiation is received by a thermopile whitened with magnesium oxyde to reflect the short wave radiation during the daytime. Wind is shielded off by a filter of «KRS 5», ground in the shape of a diffracting lens in order to better comply with the cosine law. Recording is going on continously with a dotted line recorder since March 1953, independant of weather conditions and day or night time, and is intended to be continued for a longer period. The complete measuring apparatus is calibrated absolutely in cal/cm² min. Some sample records are shown in this paper, and the qualities of the instrument are discussed.

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Microwave Remote Sensing of the Temperature and Distribution of Sulfur Compounds in the Lower Atmosphere of Venus     

Jon M. JenkinsMarc A. Kolodner  Bryan J. ButlerShady H. Suleiman  Paul G. Steffes 《Icarus》2002,158(2):312-328

A multi-wavelength radio frequency observation of Venus was performed on April 5, 1996, with the Very Large Array to investigate potential variations in the vertical and horizontal distribution of temperature and the sulfur compounds sulfur dioxide (SO₂) and sulfuric acid vapor (H₂SO₄(g)) in the atmosphere of the planet. Brightness temperature maps were produced which feature significantly darkened polar regions compared to the brighter low-latitude regions at both observed frequencies. This is the first time such polar features have been seen unambiguously in radio wavelength observations of Venus. The limb-darkening displayed in the maps helps to constrain the vertical profile of H₂SO₄(g), temperature, and to some degree SO₂. The maps were interpreted by applying a retrieval algorithm to produce vertical profiles of temperature and abundance of H₂SO₄(g) given an assumed sub-cloud abundance of SO₂. The results indicate a substantially higher abundance of H₂SO₄(g) at high latitudes (above 45°) than in the low-latitude regions. The retrieved temperature profiles are up to 25 K warmer than the profile obtained by the Pioneer Venus sounder probe at altitudes below 40 km (depending on location and assumed SO₂ abundance). For 150 ppm of SO₂, it is more consistent with the temperature profile obtained by Mariner 5, extrapolated to the surface via a dry adiabat. The profiles obtained for H₂SO₄(g) at high latitudes are consistent with those derived from the Magellan radio occultation experiments, peaking at around 8 ppm at an altitude of 46 km and decaying rapidly away from that altitude. At low latitudes, no significant H₂SO₄(g) is observed, regardless of the assumed SO₂ content. This is well below that measured by Mariner 10 (Lipa and Tyler 1979, Icarus39, 192-208), which peaked at ∼14 ppm near 47 km. Our results favor ≤100 ppm of SO₂ at low latitudes and ≤50 ppm in polar regions. The low-latitude value is statistically consistent with the results of Bézard et al. (1983, Geophs. Res. Lett.20, 1587-1590), who found that a sub-cloud SO₂ abundance of 130±40 ppm best matched their observations in the near-IR. The retrieved temperature profile and higher abundance of H₂SO₄(g) in polar regions are consistent with a strong equatorial-to-polar, cloud-level flow due to a Hadley cell in the atmosphere of Venus.  相似文献   

A Model for Structure Formation Seeded by Gravitationally Produced Matter     

Hu W  Peebles PJ 《The Astrophysical journal》2000,530(2):L61-L64

The Arecibo H i Strip Survey probed the halos of approximately 300 cataloged galaxies and the environments of approximately 14 groups with sensitivity to neutral hydrogen masses >/=107 M middle dot in circle. The survey detected no objects with properties resembling the high-velocity clouds (HVCs) associated with the Milky Way or Local Group. If the HVCs were typically MHi=107.5 M middle dot in circle objects distributed throughout groups and galaxy halos at distances of approximately 1 Mpc, the survey should have made approximately 70 HVC detections in groups and approximately 250 detections around galaxies. The null detection implies that HVCs are deployed at typical distances of 相似文献   

A modified ISBA surface scheme for modeling the hydrology of Athabasca River Basin with GCM-scale data     

Ernst Kerkhoven  Thian Yew Gan 《Advances in water resources》2006

A soil–vegetation–atmosphere transfer model (SVAT), interactions between the soil–biosphere–atmosphere (ISBA) of Météo France, is modified and applied to the Athabasca River Basin (ARB) to model its water and energy fluxes. Two meteorological datasets are used: the archived forecasts from the Meteorological Survey of Canada’s Global Environmental Multiscale Model (GEM) and the European Centre for Mid-range Weather Forecasts global re-analysis (ERA-40), representing spatial scales typical of a weather forecasting model and a global circulation model (GCM), respectively. The original treatment of soil moisture and rainfall in ISBA (OISBA) is modified to statistically account for sub-grid heterogeneity of soil moisture and rainfall to produce new, highly non-linear formulations for surface and sub-surface runoff (MISBA). These new formulations can be readily applied to most existing SVATs. Stand alone mode simulations using the GEM data demonstrate that MISBA significantly improves streamflow predictions despite requiring two fewer parameters than OISBA. Simulations using the ERA-40 data show that it is possible to reproduce the annual variation in monthly, mean annual, and annual minimum flows at GCM scales without using downscaling techniques. Finally, simulations using a simple downscaling scheme show that the better performance of higher resolution datasets can be primarily attributed to improved representation of local variation of land cover, topography, and climate.  相似文献   

Analysis and modeling of the seasonal South China Sea temperature cycle using remote sensing   总被引：1，自引：0，他引：1  

Daniel J. Twigt  Erik D. De Goede  Ernst J. O. Schrama  Herman Gerritsen 《Ocean Dynamics》2007,57(4-5):467-484

The present paper describes the analysis and modeling of the South China Sea (SCS) temperature cycle on a seasonal scale. It investigates the possibility to model this cycle in a consistent way while not taking into account tidal forcing and associated tidal mixing and exchange. This is motivated by the possibility to significantly increase the model’s computational efficiency when neglecting tides. The goal is to develop a flexible and efficient tool for seasonal scenario analysis and to generate transport boundary forcing for local models. Given the significant spatial extent of the SCS basin and the focus on seasonal time scales, synoptic remote sensing is an ideal tool in this analysis. Remote sensing is used to assess the seasonal temperature cycle to identify the relevant driving forces and is a valuable source of input data for modeling. Model simulations are performed using a three-dimensional baroclinic-reduced depth model, driven by monthly mean sea surface anomaly boundary forcing, monthly mean lateral temperature, and salinity forcing obtained from the World Ocean Atlas 2001 climatology, six hourly meteorological forcing from the European Center for Medium range Weather Forecasting ERA-40 dataset, and remotely sensed sea surface temperature (SST) data. A sensitivity analysis of model forcing and coefficients is performed. The model results are quantitatively assessed against climatological temperature profiles using a goodness-of-fit norm. In the deep regions, the model results are in good agreement with this validation data. In the shallow regions, discrepancies are found. To improve the agreement there, we apply a SST nudging method at the free water surface. This considerably improves the model’s vertical temperature representation in the shallow regions. Based on the model validation against climatological in situ and SST data, we conclude that the seasonal temperature cycle for the deep SCS basin can be represented to a good degree. For shallow regions, the absence of tidal mixing and exchange has a clear impact on the model’s temperature representation. This effect on the large-scale temperature cycle can be compensated to a good degree by SST nudging for diagnostic applications.  相似文献   

Long-term effects of anthropogenic CO<Subscript>2</Subscript> emissions simulated with a complex earth system model     

Uwe Mikolajewicz  Matthias Gröger  Ernst Maier-Reimer  Guy Schurgers  Miren Vizcaíno  Arne M. E. Winguth 《Climate Dynamics》2007,28(6):599-633

A new complex earth system model consisting of an atmospheric general circulation model, an ocean general circulation model, a three-dimensional ice sheet model, a marine biogeochemistry model, and a dynamic vegetation model was used to study the long-term response to anthropogenic carbon emissions. The prescribed emissions follow estimates of past emissions for the period 1751–2000 and standard IPCC emission scenarios up to the year 2100. After 2100, an exponential decrease of the emissions was assumed. For each of the scenarios, a small ensemble of simulations was carried out. The North Atlantic overturning collapsed in the high emission scenario (A2) simulations. In the low emission scenario (B1), only a temporary weakening of the deep water formation in the North Atlantic is predicted. The moderate emission scenario (A1B) brings the system close to its bifurcation point, with three out of five runs leading to a collapsed North Atlantic overturning circulation. The atmospheric moisture transport predominantly contributes to the collapse of the deep water formation. In the simulations with collapsed deep water formation in the North Atlantic a substantial cooling over parts of the North Atlantic is simulated. Anthropogenic climate change substantially reduces the ability of land and ocean to sequester anthropogenic carbon. The simulated effect of a collapse of the deep water formation in the North Atlantic on the atmospheric CO₂ concentration turned out to be relatively small. The volume of the Greenland ice sheet is reduced, but its contribution to global mean sea level is almost counterbalanced by the growth of the Antarctic ice sheet due to enhanced snowfall. The modifications of the high latitude freshwater input due to the simulated changes in mass balance of the ice sheet are one order of magnitude smaller than the changes due to atmospheric moisture transport. After the year 3000, the global mean surface temperature is predicted to be almost constant due to the compensating effects of decreasing atmospheric CO₂ concentrations due to oceanic uptake and delayed response to increasing atmospheric CO₂ concentrations before.  相似文献   

Risk analysis of possible impacts of climate change on South Australian wheat production     

Qunying Luo  William Bellotti  Martin Williams  Ian Cooper  Brett Bryan 《Climatic change》2007,85(1-2):89-101

This study presents a model-based risk assessment of wheat production under projected climate change by 2080 in eight locations of South Australia. The vulnerability of wheat production under future climate change was quantitatively evaluated via a risk analysis in which the identification of critical yield thresholds applies. Research results show that risk (conditional probability of not exceeding the critical yield thresholds) increased more or less across all locations under the most likely climate change. Wheat production in drier areas such as Minnipa, Orroroo and Wanbi will not be economically viable under the most likely climate change. Intensive studies on adaptation are now required.  相似文献   

Evolution of metamorphic volatiles during exhumation of microdiamond-bearing granulites in the Western Gneiss Region, Norway   总被引：1，自引：0，他引：1  

Rune B. Larsen  Elizabeth A. Eide  Ernst A. J. Burke 《Contributions to Mineralogy and Petrology》1998,133(1-2):106-121

Fluid inclusions in garnet, kyanite and quartz from microdiamond-bearing granulites in the Western Gneiss Region, Norway, document a conspicuous fluid evolution as the rocks were exhumed following Caledonian high- and ultrahigh-pressure (HP–UHP) metamorphism. The most important of the various fluid mixtures and daughter minerals in these rocks are: (N₂ + CO₂ + magnesian calcite), (N₂ + CO₂ + CH₄ + graphite + magnesian calcite), (N₂ + CH₄), (N₂ + CH₄ + H₂O), (CO₂) and (H₂O + NaCl + CaCl₂ + nahcolite). Rutile also occurs in the N₂ + CO₂ inclusions as a product of titanium diffusion from the garnet host into the fluid inclusions. Volatiles composed of N₂ + CO₂ + magnesian calcite characterise the ambient metamorphic environment between HP–UHP (peak) and early retrograde metamorphism. During progressive decompression, the mole fraction of N₂ increased in the fluid mixtures; as amphibolite-facies conditions were reached, CH₄ and later, H₂O, appeared in the fluids, concomitant with the disappearance of CO₂ and magnesian calcite. Graphite is ubiquitous in the host lithologies and fluid inclusions. Thermodynamic modelling of the metamorphic volatiles in a graphite-buffered C-O-H system demonstrates that the observed metamorphic volatile evolution was attainable only if the f _O2 increased from c. −3.5 (±0.3) to −0.8 (±0.3) log units relative to the FMQ oxygen buffer. External introduction of oxidising aqueous solutions along a system of interconnected ductile shear zones adequately explains the dramatic increase in the f _O2. The oxidising fluids introduced during exhumation were likely derived from dehydration of oceanic crust and continental sediments previously subducted during an extended period of continental collision in conjunction with the Caledonian orogeny. Received: 15 December 1997 / Accepted: 25 May 1998  相似文献   

A Similarity Model for Maximum Ground-Level Concentration in a Freely Convective Atmospheric Boundary Layer     

Bryan R. Kerman 《Boundary-Layer Meteorology》1979,16(3):395-408

A model of buoyancy- and momentum-driven industrial plumes in a freely convective boundary layer is proposed. The development combines the Lagrangian similarity models of Yaglom for non-buoyant releases in the convective surface layer with the Scorer similarity model for industrial plumes. Constraints on the validity of the extension of Yaglom’s model to the entire convective planetary boundary layer, arrived at by consideration of Batchelor’s formulation for diffusion in an inertial subrange, are often met in practice. The resulting formulation applies to an interval of time in which the entrainment of the atmosphere by the plume is balanced by the entrainment of the plume by the atmosphere. It is argued that during this interval, both maximum plume rise and ground contact are achieved. Further examination of the physical interrelationship with the Csanady-Briggs formulation serves to consolidate the model hypotheses, as well as to simplify the derivation of maximum ground-level concentrations. Experimental evidence is presented for the validity of the model, based on Moore’s published data.  相似文献