Analysis on the crystals of sea ice cores derived from Weddell Sea,Antarctica     

李志军  Nicolaus  Marcel  Toyota  Takenobu  Haas  Christian 《极地研究(英文版)》2010,21(1):1-10

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Climate change and modelling of extreme temperatures in Switzerland   总被引：3，自引：3，他引：0  

Boriss Siliverstovs  Rainald Ötsch  Claudia Kemfert  Carlo C. Jaeger  Armin Haas  Hans Kremers 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(2):311-326

This study models maximum temperatures in Switzerland monitored in twelve locations using the generalised extreme value (GEV) distribution. The parameters of the GEV distribution are determined within a Bayesian framework. We find that the parameters of the underlying distribution underwent a substantial change in the beginning of the 1980s. This change is characterised by an increase both in the level and the variability. We assess the likelihood of the heat wave of the summer 2003 using the fitted GEV distribution by accounting for the presence of a structural break. The estimation results do suggest that the heat wave of 2003 is not that statistically improbable if an appropriate methodology is used for dealing with nonstationarity.  相似文献   

Observations of the 7 March, 1970 total solar eclipse at wavelengths of 3.2 and 8.3 mm     

John P. Hagen  Paul N. Swanson  Robert W. Haas  Fred L. Wefer  Raymond W. Vogt 《Solar physics》1971,21(2):286-296

The 7 March, 1970 total solar eclipse was observed at wavelengths of 3.2 and 8.3 mm; the object being to use the knife edge of the Moon as it passed across the Sun to improve angular resolution on the Sun. This in turn would provide a radial brightness distribution of the Sun with an angular resolution of a few seconds of arc.Excellent eclipse curves were obtained at 3 mm; however, some external interference marred the 8 mm record near totality.The 8 mm brightness distribution is subject to some uncertainty, but tends to show limb brightening. The 3 mm brightness distribution shows a well defined complex limb brightening within about 1 arc min of the optical limb. The maximum brightening is approximately 30% above the average disc temperature.  相似文献   

Digital selective calling and direct printing techniques in the mobile maritime service     

de Haas  T. 《Oceanic Engineering, IEEE Journal of》1977,2(3):218-222

For a variety of reasons, communications with ships on the high seas have significantly lagged behind other communications services. For example, the maritime mobile service is practically the only service where manual Morse still constitutes a major part of the communications services. In the last few years, however, some new techniques have been developed which promise to improve maritime communications. This paper provides a background discussion of maritime mobile communications and describes two recent techniques, digital selective calling and direct printing in some detail, together with their impact on maritime communications and safety at sea. Finally, the status of and procedures for international acceptance and standardization are discussed, and national efforts to promote acceptance of these techniques are described.  相似文献   

Seasonal variations in pore water and sediment geochemistry of littoral lake sediments (Asylum Lake, MI, USA)     

Carla M Koretsky  Johnson R Haas  Douglas Miller  Noah T Ndenga 《Geochemical transactions》2006,7(1):11-26

Background  

Seasonal changes in pore water and sediment redox geochemistry have been observed in many near-surface sediments. Such changes have the potential to strongly influence trace metal distribution and thus create seasonal fluctuations in metal mobility and bioavailability.  相似文献   

Einige charakteristische Besonderheiten des geomagnetischen Sonneneruptionseffektes     

Armin Grafe 《Pure and Applied Geophysics》1958,40(1):172-179

Zusammenfassung Es werden die wichtigsten Resultate einer statischen Untersuchung des geomagnetischen Sonneneruptionseffektes wiedergegeben, der ein 65-jähriges Registriermaterial vom Observatorium Potsdam-Niemegk zugrunde liegt. Es zeigte sich einmal, daß diesfe-Häufigkeiten der 70-bis 80-jährigen Sonnenfleckenperiode folgen, und daß sie einen jahreszeitlichen Gang mit zwei Äquinoktialmaxima und einem extremen Sommerminimum besitzen. Zum anderen konnte die bekannte Ost-West-Asymmetrie der Sonnenflecken und Eruptionen auch für diesfe-erzeugenden Eruptionen nachgewiesen werden. Schließlich wurde noch eine Phasenverschiebung zwischenSQ- undsfe-Stromvektor gefunden.

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Summary The most important results of a statistical research of geomagneticsfe's are discussed, based on recordings of the observatory in Potsdam, Seddin and Niemegk during the last 65 years from 1890–1956. It is made evident that the frequency ofsfe's follows the sunspot period of 70–80 years and has an seasonal variation with two equinoctial-maxima and an extreme summer-minimun. Otherwise the well-known east-west-asymmetry of the sunspots and eruptions has been proved also for the eruptions producing thesfe's. Finally a lag of the phases betweenSQ- andsfe-current vector was found.

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Economic,institutional and technological uncertainties of emissions trading—a system dynamics modeling approach     

Irina Dolgopolova  Bo Hu  Armin Leopold  Stefan Pickl 《Climatic change》2014,124(3):663-676

System dynamics models are employed for analyzing the impact of different uncertainties on carbon emission trading–both on national and business levels. Economic, institutional and technological uncertainties significantly influence any country's benefits from emission permit trading. If a country participates in trading on the international market then the possible price range becomes the source of additional uncertainty. In the case of business investment decisions for implementing resource‐saving technology, our system dynamics model shows that the first‐mover investor will get significantly fewer advantages than his followers, which leads to delay in primary investment to the sector.  相似文献   

Properties of adjoint sea ice sensitivities to atmospheric forcing and implications for the causes of the long term trend of Arctic sea ice     

Nikolay V. Koldunov  Armin Köhl  Detlef Stammer 《Climate Dynamics》2013,41(2):227-241

Based on adjoint sensitivities of the coupled Massachusetts Institute of Technology ocean–sea ice circulation model, the potential influence of thermodynamic atmospheric forcing on the interannual variability of the September sea ice area (AREA) and volume (VOLUME) in the Arctic is investigated for the three periods 1980–1989, 1990–1999 and 2000–2009. Sensitivities suggest that only large forcing anomalies prior to the spring melting onset in May can influence the September sea ice characteristics while even small changes in the atmospheric variables during subsequent months can significantly influence September sea ice state. Specifically, AREA close to the ice edge in the Arctic seas is highly sensitive to thermodynamic atmospheric forcing changes from June to July. In contrast, VOLUME is highly sensitive to atmospheric temperature changes occurring during the same period over the central parts of the Arctic Ocean. A comparison of the sea ice conditions and sensitivities during three different periods reveals that, due to the strong decline of sea ice concentration and sea ice thickness, sea ice area became substantially more sensitive to the same amplitude thermodynamic atmospheric forcing anomalies during 2000–2009 relative to the earlier periods. To obtain a quantitative estimate of changes that can be expected from existing atmospheric trends, adjoint sensitivities are multiplied by monthly temperature differences between 1980s and two following decades. Strongest contributions of surface atmospheric temperature differences to AREA and VOLUME changes are observed during May and September. The strongest contribution from the downward long-wave heat flux to AREA changes occurs in September and to VOLUME changes in July–August. About 62 % of the AREA decrease simulated by the model can be explained by summing all contributions to the thermodynamic atmospheric forcing. The changing sea ice state (sensitivity) is found to enhance the decline and accounts for about one third of the explained reduction. For the VOLUME decrease, the explained fraction of the decrease is only about 37 %.  相似文献   

An improved fast level set method initialized with a combination of k-means clustering and Otsu thresholding for unsupervised change detection from SAR images     

Armin Moghimi  Safa Khazai  Ali Mohammadzadeh 《Arabian Journal of Geosciences》2017,10(13):293

Detection of changes in synthetic aperture radar (SAR) images is an important challenge due to the effects of speckle noise on these images. In recent years, appropriate methods for SAR-based-change detection have been developed based on the level set methods (LSM). These methods need to set parameters for defining a proper initial contour. Moreover, the gradient information is only employed in the total energy of these methods for segmentation of the difference image. In this study, a novel method has been proposed for unsupervised change detection of multitemporal SAR images based on the improved fast level set method (IFLSM) initialized with a combination of k-means and Otsu techniques. The proposed method utilizes the discrete wavelet transform (DWT) fusion strategy and edge enhancement to achieve a noise-resistant difference image from the mean-ratio and log-ratio images. Afterward, the generated binary change map (CM) by applying a combination of k-means and Otsu techniques on the difference image is used as the initial contour to achieve a final CM on difference image using the IFLSM. To check advantages of the proposed method, experiments are applied on two sets of multitemporal SAR images corresponding to artificial Chitgar Lake (under reconstruction) in Tehran (Iran) taken by TerraSAR-X satellite in 2011 and 2012, and corresponding to San Pablo and Briones reservoirs in California (USA) acquired by ERS-2 satellite in 2003 and 2004. Results of proposed method were compared with results of some well-known unsupervised change detection methods. Experimental results prove the sufficiency of the proposed method in unsupervised change detection in terms of accuracy, implementation time, and computational complexity.  相似文献