Titan's surface at 2.2-cm wavelength imaged by the Cassini RADAR radiometer: Calibration and first results

The first comprehensive calibration and mapping of the thermal microwave emission from Titan's surface is reported based on radiometric data obtained at 2.2-cm wavelength by the passive radiometer included in the Cassini Radar instrument. The data reported were accumulated from 69 separate observational segments in Titan passes from Ta (October 2004) through T30 (May 2007) and include emission from 94% of Titan's surface. They are diverse in the key observing parameters of emission angle, polarization, and spatial resolution, and their reduction into calibrated global mosaic maps involved several steps. Analysis of the polarimetry obtained at low to moderate resolution (50+ km) enabled integration of the radiometry into a single mosaic of the equivalent brightness temperature at normal incidence with a relative precision of about 1 K. The Huygens probe measurement of Titan's surface temperature and radiometry obtained on Titan's dune fields allowed us to infer an absolute calibration estimated to be accurate to a level approaching 1 K. The results provide evidence for a surface that is complex and varied on large scales. The radiometry primarily constrains physical properties of the surface, where we see strong evidence for subsurface (volume) scattering as a dominant mechanism that determines the emissivity, with the possibility of a fluffy or graded-density surface layer in many regions. The results are consistent with, but not necessarily definitive of a surface composition resulting from the slow deposition and processing of organic compounds from the atmosphere.     

Temperature changes on the Tibetan Plateau during the past 600 years inferred from ice cores and tree rings

The climatological signal of δ¹⁸O variations preserved in ice cores recovered from Puruogangri ice field in the central Tibetan Plateau (TP) was calibrated with regional meteorological data for the past 50 years. For the period AD 1860–2000, 5-yearly averaged ice core δ¹⁸O and a summer temperature reconstruction derived from pollen data from the same ice core were compared. The statistical results provide compelling evidence that Puruogangri ice core δ¹⁸O variations represent summer temperature changes for the central TP, and hence regional temperature history during the past 600 years was revealed. A comparison of Puruogangri ice core δ¹⁸О with several other temperature reconstructions shows that broad-scale climate anomalies since the Little Ice Age occurred synchronously across the eastern and southern TP, and the Himalayas. Common cold periods were identified in the 15th century, 1625–1645 AD, 1660–1700 AD, 1725–1775 AD, 1795–1830 AD, 1850–1870 AD, 1890–1920 AD, 1940–1950 AD, and 1975–1985 AD. The period 1725–1775 AD was one of the most prolonged cool periods during the past 400 years and corresponded to maximum Little Ice Age glacier advance of monsoonal temperate glaciers of the TP.     

Biogeochemistry of particulate organic matter from lakes of different trophic levels in Switzerland

Biomarker compositions of particulate organic matter (POM) from the oligotrophic Lake Brienz and the eutrophic Lake Lugano (both Switzerland) are compared, in order to obtain information about organic matter (OM) production and transformation processes in relation to water column stratification. Eutrophic conditions in Lake Lugano are reflected by enhanced alkalinity, elevated total organic carbon (TOC) and chlorin contents compared with Lake Brienz. Lower δ¹³C values of dissolved inorganic carbon (DIC) in Lake Lugano reflect enhanced OM respiration in the water column.Differences in OM dynamics between both lakes, as well as seasonal variations, are evidenced by TOC-normalised concentration profiles of total fatty acids (FAs) and total neutrals. In Lake Brienz, the results reflect the relative contributions of primary productivity and refractory, allochthonous OM to POM, governed by particle load and interflows due to density stratification. The depth trends at Lake Lugano are a result of high primary productivity, water column stratification and associated particle load in the upper layers, as well as microbially induced degradation close to the chemocline and greater preservation under anoxic conditions. Minor differences exist with regard to the OM composition. In both lakes, FA distributions and the composition of n-alkanols indicate a predominant autochthonous OM source (algae, zooplankton, bacteria). Inputs of OM from diatoms are reflected in highly-branched isoprenoid (HBI) alkenes, 16:1 n-FAs and 24-methylcholesta-5,22-dien-3β-ol (either epibrassicasterol or brassicasterol). Differences in relative proportions of n-C₁₆ vs. n-C₁₈ FAs and alkanols, respectively, as well as in the percentages of C₂₇, C₂₈ and C₂₉ sterols relative to the sum of sterols are related to differences in the abundances of chrysophytes, diatoms and green algae within the euphotic zone of both lakes as well as in bacterial activity and soil in-wash. High relative proportions of cholesterol in the autumn samples, most pronounced at Lake Lugano, were attributed to an increased input from zooplankton grazing in the water column.Differences in OM degradation processes are reflected in slightly higher chlorin index values and higher relative proportions of saturated vs. unsaturated n-FAs in Lake Lugano. Higher contents of branched chain FAs, 16:1ω7 n-FA, and enhanced 18:1ω7/18:1ω9 n-FA ratios suggest enhanced bacterial biomass in the water column of Lake Lugano close to the chemocline. Increasing proportions of saturated n-FAs and n-alkanols with increasing water depth, most distinct in the autumn for both lakes, argue for intensified bacterial activity and degradation of OM during autumn. High relative contents of sterols and low n-alkanol concentrations in POM close to the chemocline at Lake Lugano during spring are interpreted to reflect higher primary productivity in the photic zone, OM export to the deeper parts and enhanced degradation rates of more labile constituents (i.e. C₁₃–C₂₀ n-alkanols), as compared to Lake Brienz.     

CoRoT/ESTA–TASK 1 and TASK 3 comparison of the internal structure and seismic properties of representative stellar models

We compare stellar models produced by different stellar evolution codes for the CoRoT/ESTA project, comparing their global quantities, their physical structure, and their oscillation properties. We discuss the differences between models and identify the underlying reasons for these differences. The stellar models are representative of potential CoRoT targets. Overall we find very good agreement between the five different codes, but with some significant deviations. We find noticeable discrepancies (though still at the per cent level) that result from the handling of the equation of state, of the opacities and of the convective boundaries. The results of our work will be helpful in interpreting future asteroseismology results from CoRoT.     

Tremblements de terre et anomalies magnétiques

Résumé On a déjà souvent signalé que le champ magné ique terrestre s'est trouvé modifié de fa?on durable à la suile de mouvements séismiques. L'auteur rappelle plusieurs exemples récents d'anomalies magnétiques mesurées au Japon à la suite d'importants séismes (Kato). L'anomalie magnélique duBassin de Paris se déforme dans le temps en liaison possible avec des déplacements magmatiques et une activité séismique avortée. Le séisme du 11 juin 1938 en Belgique montre d'intéressants rapports avec l'anomalie magnétique belge. Les cartes isoporiques mondiales présentent des relations avec les cartes de séismicité (Omer). L'auteur pense que séismes et déformations du champ magnétique terrestre sont plus ou moins étroitement liés et que peut être une réaction atomiqueen chaine peut expliquer les séismes orogéniques et leurs répliques.

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Summary It was yet often noted that the earth's magnetic field has been steadily modified on the result of seismic earth movements. The author cites many recent examples of magnetic anomalies measured in Japan after major earthquakes (Kato). The ?Bassin de Paris?'s magnetic anomaly is modified during a certain time in a possible connection with magmatic removals and with some seismic activity. The earthquake of June 11 th., 1938 in Belgium shows some very interesting connections with the belgian magnetic anomaly. Suggestive relationships are noted between changes in the earth's secular magnetic field and areas of seismicity (Omer). The author thinks that the earthquakes and the deformations of the earth's magnetic field are more or less closely connected one with another, and it may perhaps be that the atomic energy (chain reactions) may explain some orogenic earthquakes and their aftershocks.

     

Konstruktive und thermodynamische Eigenschaften des Piche-Evaporimeters

Zusammenfassung Im ersten Teil der Arbeit werden der Einfluß von Temperaturänderungen auf die Anzeige des Piche-Evaporimeters und der Einfluß des Lochdurchmessers im Filterpapier auf den Unterdruck im Rohr untersucht. In beiden Fällen ergibt sich eine sehr gute Übereinstimmung zwischen dem experimentellen Ergebnis und entsprechenden theoretischen Überlegungen.Messungen der Verdunstung des Piche-Evaporimeters, bei denen die Strahlung durch eine äquivalente elektrische Heizung des Filterpapiers ersetzt wurde, erlauben zusammen mit den Messungen der übrigen für die Verdunstung maßgebenden Parameter die Bestimmung der Wärmeübergangszahl des Filterpapierblättchens des Piche-Evaporimeters als Funktion der Windgeschwindigkeit. Das dabei gefundene Potenzgesetz, welches weitgehend den aus der Literatur bekannten Formeln für die Wärmeübergangszahl folgt, ermöglicht es, die Verdunstung und die Mitteltemperatur des Filterpapiers des Piche-Evaporimeters mit Hilfe der vonG. Hofmann angegebenen Formeln und der in ihnen auftretenden meteorologischen Parameter (Lufttemperatur, Windgeschwindigkeit, Strahlungsbilanz, relative Luftfeuchtigkeit) zu errechnen. Auch hier ergibt sich eine sehr gute Übereinstimmung der berechneten Werte mit den gemessenen, so daß die Abhängigkeit der Meßwerte eines Piche-Evaporimeters von den für dessen Anzeige maßgebenden Parametern hinreichend geklärt erscheint.

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Summary First are investigated the effect of temperature variations on the readings of a Piche evaporimeter, and the effect of the size of the hole pierced into the filter paper on the underpressure within the tube. In both cases good agreement is found between experimental results and theoretical considerations.The heat transfer coefficient of the filter paper as a function of wind velocity was ascertained by observing evaporation and the pertinent parameters; radiation, however, was replaced by an equivalent electric heating of the filter paper. The relationship follows a power law and corresponds largely with other formulae given in the literature. By applyingG. Hofmann's formulae (containing air temperature, wind velocity, net radiation, and relative humidity) the relationship can be used to calculate the mean temperature of the filter paper and the amount of evaporation. The agreement between calculated and observed results is very good. It seems, therefore, that the relationship between the Piche evaporimeter readings and the meteorological parameters governing its reactions is sufficiently clarified.

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Résumé On étudie tout d'abord l'influence des variations de température sur les indications de l'évaporimètre de Piche, ainsi que l'effet du diamètre du trou du papier-filtre sur la dépression du tube. Dans les deux cas la théorie et l'expérience sont parfaitement d'accord.En mesurant ensuite l'évaporation de l'instrument exposé à un chauffage électrique équivalent à la radiation et en tenant compte des autres paramètres, on peut déterminer le coefficient de transfert de chaleur du filtre en fonction de la vitesse du vent. La loi exponentielle trouvée qui correspond bien aux formules connues pour le transfert de chaleur, permet alors de calculer l'évaporation et la température moyenne du filtre à l'aide des formules données parG. Hofmann et des paramètres météorologiques (température de l'air, vitesse du vent, bilan radiatif, humidité relative). Là aussi, l'accord entre la théorie et l'expérience est très satisfaisant, ce qui établit convenablement et de façon suffisante le lien entre les indications de l'évaporimètre de Piche et les conditions d'expérience.

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Mit 10 TextabbildungenTeil einer Diplomarbeit für Meteorologie an der Universität München (1959).     

沈北煤田煤中琥珀的植物来源和稳定同位素的古环境意义

琥珀是由古代植物代谢产生的树脂聚合物形成的化石。琥珀中的有机质保存环境稳定、封闭,能很好地记载其形成时期的古植物和古环境等信息。本次研究运用气象色谱质谱联用仪（GC-MS）和元素分析稳定同位素质谱仪（EA-IRMS）等测试方法,研究了沈北煤田煤中琥珀的有机地球化学组成、稳定同位素和化合物单体碳同位素特征。结果表明,琥珀中的饱和烃以二萜化合物为主（占73.45%）,芳香烃以松香烷型化合物为主（56.17%）;高含量的贝壳杉烷、雪松烷、扁枝烷和松香烷型化合物指示琥珀来源于松柏类植物,且以柏科植物为主。沈北琥珀的δ13C值为-22.8‰ ~ -21.2‰,与同时期其他地区琥珀的δ13C值相似;氢同位素变化范围较小（-297.2‰ ~ -276.0‰）,氧同位素值为17.4‰ ~ 31.6‰。琥珀的稳定同位素组成（碳、氢和氧）进一步证明琥珀来源于裸子植物。琥珀的δ13C值主要与其形成时的全球气温变化和大气组成有关。沈北琥珀的氢和氧同位素组成主要受植物种类（松柏类）以及植物生长的局部气温和降水条件有关。琥珀稳定碳同位素有望成为研究古气候和古大气组成的良好载体,琥珀的氢和氧同位素可以反映形成时期的古环境条件,但仍需进一步深入研究。     

Geostrophic Wind, Gradient Wind, Thermal Wind And The Vertical Wind Profile – A Sample Analysis Within A Planetary Boundary Layer Over Arctic Sea-Ice

For the interpretation of many boundary-layer field experiments the geostrophic wind is needed as an external parameter. However, quite often and especially in remote areas this wind is not known at all or difficult to determine because there are not enough measurements of the surface pressure.Here it is shown how measurements carried out with the HELIPOD system, a helicopter-borne meteorological turbulence measuring system, may be used to evaluate the geostrophic wind. This is done by the analysis of the pressure field at different heights. An additional analysis of the temperature field in the same heights allows for the discussion of the quality of the derived geostrophic wind. An intercomparison with the vertical wind profile enables us to discuss the influence of the curvature of the isobars. From this, finally, also the gradient wind can be estimated.