A decadal microwave record of tropical air temperature from AMSU-A/aqua observations     

Yuan Shi  King-Fai Li  Yuk L. Yung  Hartmut H. Aumann  Zuoqiang Shi  Thomas Y. Hou 《Climate Dynamics》2013,41(5-6):1385-1405

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On the mass-to-light ratio of the local Galactic disc and the optical luminosity of the Galaxy     

Chris Flynn  Johan Holmberg  Laura Portinari  Burkhard Fuchs  Hartmut Jahreiß 《Monthly notices of the Royal Astronomical Society》2006,372(3):1149-1160

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The composite galaxy NGC 6764: Nuclear activity and circumnuclear star formation     

Berto Boer  Hartmut Schulz 《Astrophysics and Space Science》1990,163(2):201-210

We investigated the kinematics and ionization mechanism of the innermost arc seconds of the nucleus of NGC 6764 (SBb), using spatially-resolved optical spectra. The observed radial variations of the emission line ratios cannot be explained by one single-ionizing agent, but are consistent with circumnuclear ionizeation by hot stars in addition to a central power-law source. We conclude that NGC 6764 is a Composite Galactic Nucleus (CGN).Visiting Astronomer, German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie in Heidelberg jointly with the Spanish National Commission for Astronomy.  相似文献   

DRIVING FORCES OF ISLAND BIODIVERSITY: AN APPRAISAL OF TWO THEORIES     

Hartmut S. Walter 《自然地理学》2013,34(5):351-377

The avifauna of three oceanic islands of the Revillagigedo archipelago in the eastern Pacific Ocean consists of 14 endemic landbird taxa and 3 recent continental colonists. This study analyzes the origin, areography of continental relatives, ecological characteristics, and role of immigration and extinction factors as regulators of the islands' species. Only two natural extinctions have been detected on this archipelago in more than 130 years. The endemic nature of the pristine avifauna is interpreted as an indication of high stability over thousands of years. The MacArthur–Wilson (1967) “equilibrium theory of island biogeography” cannot explain or predict the persistence of this avifauna adapted to stable and unique island ecosystems. Lack's (1976) “theory of ecological poverty” regulating island avifaunas, however, predicts stability and a resource-limited bird community. The Revillagigedo avifauna can be understood as an interactive community of a few highly adapted and competitive ecological generalists that have effectively filled all niche spaces and closed off the islands to further colonization. Catastrophic change or anthropogenic landscape degradation may, however, create novel niche spaces and open affected islands to new colonists. This appraisal lends support to the call for a shift away from application of the equilibrium model of island biogeography in conservation science. [Key words: island biogeography, equilibrium theory, island stability, island avifauna, MacArthur-Wilson, Lack, Revillagigedo Islands, Socorro Island.]  相似文献   

Elastic and Seismic Properties of Dabie-Sulu Ultrahigh Pressure Metamorphic Rocks     

WANG Qian  JI Shaocheng  SUN Shengsi  Matthew H. SALISBURY  Hartmut KERN 《《地质学报》英文版》2012,86(1):20-37

Lamé modulus (λ) and shear modulus (μ) are among the most important,intrinsic,elastic constants of rocks.Using λ and μ could be much more advantageous than using P- and S-wave velocities (Vp and Vs).He...  相似文献   

Sedimentology and geochemistry of an exceptionally preserved last interglacial sapropel S5 in the Levantine Basin (Mediterranean Sea)     

Tobias Moller  Hartmut Schulz  Yvonne Hamann  Olaf Dellwig  Michal Kucera 《Marine Geology》2012

A combined study of lithological, geochemical and physical sediment properties is reported from a completely laminated S5 sapropel, recovered in three gravity cores (M40-4 SL67, M51-3 SL103, M51-3 SL104) from the Pliny Trench region of the eastern Mediterranean. The thickness of the studied sapropel S5 varies between 85 and 91 cm and tops most S5-sapropels in the Mediterranean. Based on optical features like color and thickness of laminae, the sapropels were subdivided into thirteen distinct lithostratigraphic zones. These zones, as well as the finer layering pattern within them, could be followed exactly among the three cores, indicating that the processes responsible for this variation acted at least on a regional scale. The sapropel sediment is characterized by exceptionally high porosity, which is strongly correlated with Si/Ca. This relationship implies that the sapropel is in essence an organic-matter rich diatomite and its exceptional thickness can be explained by preservation of diatoms forming a loosely packed sediment fabric. Compared to other S5 sapropels, the preservation of diatoms has apparently led to a twofold increase in the thickness of the sapropel layer. Relative abundances of 10 elements were determined at ultra-high resolution (0.2 mm) by XRF-scanner over the complete length of each sapropel including several cm of enclosing marl. An analysis of the chemical data indicates that the lowermost 13 cm of the sapropel is chemically more similar to the underlying marl and that the sediment chemistry shows different signals at different scales. The strongest pattern is the contrast between the sapropel and the surrounding marl, which is accentuated in elements indicative for redox conditions as well as terrigenous sediment input and productivity. Within the sapropel, a mm- to cm-scale layering is observed. The abundances of many elements are systematically linked to the pattern of these layers, indicating a common origin, related to productivity and/or terrigenous sediment and/or redox conditions. This pattern indicates a link to a regional climatic process, making the S5 sapropel horizon in M40-4 SL67, M51-3 SL103 and M51-3 SL104 a potential high-resolution archive of climatic variability during the last interglacial in the Mediterranean Sea and its adjacent landmasses.  相似文献   

Improved Recharge Estimation from Portable,Low‐Cost Weather Stations          下载免费PDF全文

Hartmut M. Holländer  Zijian Wang  Kibreab A. Assefa  Allan D. Woodbury 《Ground water》2016,54(2):243-254

Groundwater recharge estimation is a critical quantity for sustainable groundwater management. The feasibility and robustness of recharge estimation was evaluated using physical‐based modeling procedures, and data from a low‐cost weather station with remote sensor techniques in Southern Abbotsford, British Columbia, Canada. Recharge was determined using the Richards‐based vadose zone hydrological model, HYDRUS‐1D. The required meteorological data were recorded with a HOBO^TM weather station for a short observation period (about 1 year) and an existing weather station (Abbotsford A) for long‐term study purpose (27 years). Undisturbed soil cores were taken at two locations in the vicinity of the HOBO^TM weather station. The derived soil hydraulic parameters were used to characterize the soil in the numerical model. Model performance was evaluated using observed soil moisture and soil temperature data obtained from subsurface remote sensors. A rigorous sensitivity analysis was used to test the robustness of the model. Recharge during the short observation period was estimated at 863 and 816 mm. The mean annual recharge was estimated at 848 and 859 mm/year based on a time series of 27 years. The relative ratio of annual recharge‐precipitation varied from 43% to 69%. From a monthly recharge perspective, the majority (80%) of recharge due to precipitation occurred during the hydrologic winter period. The comparison of the recharge estimates with other studies indicates a good agreement. Furthermore, this method is able to predict transient recharge estimates, and can provide a reasonable tool for estimates on nutrient leaching that is often controlled by strong precipitation events and rapid infiltration of water and nitrate into the soil.  相似文献   

A box model of circulation and melting in ice shelf caverns     

Dirk Olbers  Hartmut Hellmer 《Ocean Dynamics》2010,60(1):141-153

A simple box model of the circulation into and inside the ocean cavern beneath an ice shelf is used to estimate the melt rates of Antarctic glaciers and ice shelves. The model uses simplified cavern geometries and includes a coarse parameterization of the overturning circulation and vertical mixing. The melting/freezing physics at the ice shelf/ocean interface are those usually implemented in high-resolution circulation models of ice shelf caverns. The model is driven by the thermohaline inflow conditions and coupling to the heat and freshwater exchanges at the sea surface in front of the cavern. We tune the model for Pine Island Glacier and then apply it to six other major caverns. The dependence of the melting rate on thermohaline conditions at the ice shelf front is investigated for this set of caverns, including sensitivity studies, alternative parameterizations, and warming scenarios. An analytical relation between the melting rate and the inflow temperature is derived for a particular model version, showing a quadratic dependence of basal melting on small values of the temperature of the inflow, which changes to a linear dependence for larger values. The model predicts melting at all ice shelf bases in agreement with observations, ranging from below a meter per year for Ronne Ice Shelf to about 25 m/year for the Pine Island Glacier. In a warming scenario with a one-degree increase of the inflow temperature, the latter glacier responds with a 1.4-fold increase of the melting rate. Other caverns respond by more than a tenfold increase, as, e.g., Ronne Ice Shelf. The model is suitable for use as a simple fast module izn coarse large-scale ocean models.  相似文献   

Regional and global effects of southern ocean constraints in a global model     

Michael P. Schodlok  Manfred Wenzel  Jens G. Schröter  Hartmut H. Hellmer 《Ocean Dynamics》2008,58(3-4):155-168

Global ocean circulation models do not usually take high-latitude processes into account in an adequate form due to a limited model domain or insufficient resolution. Without the processes in key areas contributing to the lower part of the global thermohaline circulation, the characteristics and flow of deep and bottom waters often remain unrealistic in these models. In this study, various sections of the Bremerhaven Regional Ice Ocean Simulation model results are combined with a global inverse model by using temperature, salinity, and velocity constraints for the Hamburg Large Scale Geostrophic ocean general circulation model. The differences between the global model with and without additional constraints from the regional model demonstrate that the Weddell Sea circulation exerts a significant influence on the course of the Antarctic Circumpolar Current with consequences for Southern Ocean water mass characteristics and the spreading of deep and bottom waters in the South Atlantic. The influence of the Ross Sea is found to be less important in terms of global influences. However, regional changes in the Pacific sector of the Southern Ocean are found to be of Ross Sea origin. The additional constraints change the hydrographic conditions of the global model in the vicinity of the Antarctic Circumpolar Current in such a way that transport values, e.g., in Drake Passage no longer need to be prescribed to obtain observed transports. These changes not only improve the path and transport of the Antarctic Circumpolar Current but affect the meso- and large-scale circulation. With a higher (lower) mean Drake Passage transport, the mean Weddell Gyre transport is lower (higher). Furthermore, an increase (decrease) in the Antarctic Circumpolar Current leads to a decrease (increase) of the circum-Australian flow, i.e., a decrease (increase) of the Indonesian Throughflow.  相似文献   

Reaktionen benthischer Tiefsee-Lebensgemeinschaften auf mechanische Störungen der Sedimente     

Bluhm  Hartmut  Borowski  Christian  Ahnert  Ahmed  Vopel  Kay  Schriever  Gerd  Thiel  Hjalmar 《Ocean Dynamics》1999,51(10):149-152

Ocean Dynamics - Das Ökosystem der Tiefsee wird zunehmend durch industrielle Eingriffe beeinflusst. Über die Auswirkungen dieser Aktivitäten auf das Benthos wurden bisher nur...  相似文献