CME Projection Effects Studied with STEREO/COR and SOHO/LASCO

Based on a set of 11 CME events we study the impact of projection effects by tracking CME leading edge features in the plane of sky (traditional CME tracking) from combined STEREO-SECCHI and SOHO-LASCO observations up to 20R _⊙. By using CME observations from two vantage points and applying triangulation techniques, the source region location of the CME on the solar surface was determined (heliospheric longitude and latitude) to correct for projection effects. With this information, the directivity and “true” speed of a CME can be estimated in a simple way. The comparison of the results obtained from the spacecraft pairs SOHO-LASCO/STEREO-A and SOHO-LASCO/STEREO-B allows us to study the reliability of the method. The determined CME source region is generally coincident within ?10°.     

Experimental observation of strong mixing due to internal wave focusing over sloping terrain

This paper reports on experimental observation of internal waves that are focused due to a sloping topography. A remarkable mixing of the density field was observed. This result is of importance for the deep ocean, where internal waves are believed to play a role in mixing. The experiments were performed on the rotating platform at the Coriolis Laboratory, Grenoble. The rotation, its modulation and density stratification were set to be in the internal wave regime. After applying various data processing techniques we observe internal wave rays, which converge to a limiting state: the wave attractor. At longer time scales we observe a remarkably efficient mixing of the density field, possibly responsible for driving observed sheared mean flows and topographic Rossby waves. We offer the hypothesis that focusing of internal waves to the wave attractor leads to the mixing.     

Impacts of irrigation on dry season precipitation in India

There is a lack of observed data-based studies examining the role of enhanced soil moisture conditions (due to irrigation) on the prevailing precipitation. Therefore, in the present study, we have examined the impacts of the Green Revolution (GR) related expansion of irrigation and changes in dry season (the rabi (November to May) and the zaid (March to June)) precipitation in India. The results for some regions indicated decreasing and increasing trend in precipitation during the pre- and post-GR periods, respectively. For example, in eastern Madhya Pradesh, the pre- and post-GR precipitation trends for the zaid season were ?0.45 and 2.40?mm?year^?1, respectively. On the other hand, some regions reported lower rate of decline in precipitation during the post-GR period. This paper suggests that both positive and lower declining trend during the post-GR period were linked to increased precipitation due to the introduction of irrigation. The study has found up to 69?mm (121%) increase in total amount of precipitation for growing seasons during the post-GR period. Moreover, a 175% increase in average precipitation was also recorded. All irrigated regions show a notable increase in precipitation during post-GR growing seasons. It was found that differences in growing season average precipitation between the pre- and post-GR periods were statistically significant for most of the regions. For further verification of results, the MM5 and Noah land surface model were applied. These applications show changes in precipitation and various precipitation controlling factors due to changes in soil moisture.     

A comparison of long-term parallel measurements of sunshine duration obtained with a Campbell-Stokes sunshine recorder and two automated sunshine sensors

Theoretical and Applied Climatology - In recent decades, automated sensors for sunshine duration (SD) measurements have been introduced in meteorological networks, thereby replacing traditional...     

Multi-Wavelength Signatures of Magnetic Reconnection of a Flare-Associated Coronal Mass Ejection

The evolution of an X2.7 solar flare, that occurred in a complex β γ δ magnetic configuration region on 3 November 2003 is discussed by utilizing a multi-wavelength data set. The very first signature of pre-flare coronal activity is observed in radio wavelengths as a type III burst that occurred several minutes prior to the flare signature in Hα. This type III burst is followed by the appearance of a loop-top source in hard X-ray (HXR) images obtained from RHESSI. During the main phase of the event, Hα images observed from ARIES solar tower telescope, Nainital, reveal well-defined footpoint (FP) and loop-top (LT) sources. As the flare evolves, the LT source moves upward and the separation between the two FP sources increases. The co-alignment of Hα with HXR images shows spatial correlation between Hα and HXR footpoints, whereas the rising LT source in HXR is always located above the LT source seen in Hα. The evolution of LT and FP sources is consistent with the reconnection models of solar flares. The EUV images at 195 Å taken by SOHO/EIT reveal intense emission on the disk at the flaring region during the impulsive phase. Further, slow-drifting type IV bursts, observed at low coronal heights at two time intervals along the flare period, indicate rising plasmoids or loop systems. The intense type II radio burst at a time in between these type IV bursts, but at a relatively greater height, indicates the onset of CME and its associated coronal shock wave. The study supports the standard CSHKP model of flares, which is consistent with nearly all eruptive flare models. More importantly, the results also contain evidence for breakout reconnection before the flare phase.     

Examination of diatom-based changes from a climatically sensitive prairie lake (Saskatchewan, Canada) at different temporal perspectives

Paleoclimatic records from the climatically sensitive Canadian prairies are relatively rare due to the scarcity of study sites with continuous Holocene stratigraphic sequences. Oro Lake, a meromictic lake in the dry grasslands of Saskatchewan (Canada), contains a continuous Holocene diatom record spanning the last 10,000 years. Here we present analyses at three different time scales and resolution: (1) 1–3 yr resolution of the past 80 years, (2) century-scale analysis of the Holocene, and (3) decadal-scale analysis of the past 7000 years. Recent changes in the diatom assemblages and their respective salinity inferences were significantly related to measured effective moisture (precipitation minus evaporation, P−ET). The droughts of the 1930s, and a wet period during the 1950s are clearly evident in the diatom record, suggesting the Oro Lake record contains a sensitive archive of past climatic conditions. Century-scale analysis of the diatom record during the Holocene is consistent with a cool and moist climate in the early Holocene (prior to ca 9700 cal yr BP, 8600 ¹⁴C yr BP). An abrupt increase in diatom-inferred salinity at 9600 cal yr BP (8500 ¹⁴C yr BP) indicates the onset of an arid climate, with continuing arid conditions throughout the mid-Holocene. Decadal-scale analysis of the past 7000 years suggests that the mid-Holocene was more complex, with extended periods of increased variability in precipitation, particularly between ca 5800–3600 cal yr BP (5000–3200 ¹⁴C yr BP) which is characterized by intervals of increased effective moisture. The past 2000 years is characterized by reduced salinities and generally wetter conditions in comparison to the mid-Holocene. The combination of the different scales of analyses in this study provides a detailed account of the dynamic nature of climate from sub-decadal to millennial scale in the Oro Lake region within the Palliser Triangle. Climate model predictions suggest that the Canadian prairie region may see a higher frequency of extreme droughts under projected global warming, potentially similar to the most arid periods seen during the mid-Holocene when many lake basins completely dried out.     

南大西洋中脊26°S热液区成矿物质来源探讨

南大西洋中脊的26°S热液区广泛发育多金属硫化物、底泥、枕状熔岩、非活动性烟囱体和活动性烟囱体。为了有效探索硫、铜等成矿物质的来源以及成矿作用过程,分别以玄武岩、烟囱体残片及块状多金属硫化物为研究对象,开展了熔融包裹体、硫同位素和铜同位素研究。结果显示：区内玄武岩新鲜未蚀变且斑晶中产出大量熔融包裹体;熔融包裹体气泡壁附着黄铜矿、黄铁矿及磁铁矿等子矿物,说明在岩浆作用过程中可从熔浆中分离出成矿所需的金属元素和硫,这些成矿元素随着岩浆去气作用进入挥发分中,并随着脱气作用迁移出来。通过对烟囱体残片及块状多金属硫化物中黄铁矿的硫同位素组成进行比对分析,发现26°S热液区内硫化物的硫同位素与大西洋各热液区硫化物的硫同位素变化范围相一致,但δ³⁴S_V-CDT值略低（3.0‰~3.9‰）。低的δ³⁴S_V-CDT值指示硫以岩浆硫源为主,海水硫酸盐还原硫占比低。黄铜矿呈现略微富铜重同位素特征且分馏程度较低,其δ⁶⁵Cu值（0.171‰~0.477‰）趋近于大洋中脊玄武岩的铜同位素值（0）。综合硫同位素及铜同位素特征,表明热液流体经历了岩浆和海水的混合过程,成矿物质主要来自于岩浆热液,成矿作用过程中可能有少量海水混入。     

Numerical solution of nonlinear equations in chemical speciation calculations

Speciation calculations involve the computation of the concentration of each individual chemical species in a multicomponent–multiphase chemical system. The numerical problem is to solve a system of coupled linear and nonlinear equations subject to the constraint that all unknowns are positive. The performance and accuracy of a series of nonlinear equation solvers are evaluated: A quasi-Newton method with the global step determined by different line search and trust region algorithms, the conjugate gradient method with the global step determined by line search, and the solvers in the codes TENSOLVE, CONMIN and LBFGS.     

Polychlorinated biphenyls (PCB) and organochlorine pesticides in sediments of the baltic and coastal waters of Mecklenburg-Vorpommern

Summary The distribution of polychlorinated biphenyls (PCB) and organochlorine pesticides, e.g. the isomers of hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), p,p’-dichiorodiphenyitrichloroethane (DDT) and its primary metabolites DDE and DDD was investigated in surface sediments (0–2 cm) and sediment cores (0–45 cm) from the western Baltic Sea and the coastal waters of Mecklenburg-Vorpommern. Sediment sampling was carried out in the Belt Sea, the Arkona Basin, the Pomeranian Bight and in almost all Bodden and Haff areas of Mecklenburg-Vorpommern in autumn 1993 and 1994. The highest concentrations of PCB and DDT compounds, measured in the innercoastal waters, reached 214 ng g^-1 dry weight (d. w.). The values of HCH isomers ranged between 0.01 and 2.9 ng g^-1 d.w., the highest levels being those of Β-HCH. Levels of chlorinated hydrocarbons, which varied depending on the sediment properties, indicated increased riverine inputs (Oder, Peene, and Uecker). Elevated levels in the Oderhaff and Peenestrom characterize that area as a sink and, due to remobilization of the upper sediment layer (fluffy layer) into the pelagic, also as a source of organic contaminants. Input from agriculture and industrial point sources (shipyards, shipbuilding) was observed in the coastal waters. The homogeneous PCB and DDT distribution (TOC standardization) observed in the surface sediments of some areas in the western Baltic indicates high sediment dynamics. This is supported by the results of sediment core analyses which showed a constant PCB and DDT distribution down to a depth of 15 to 20 cm.

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Polychlorierte Biphenyle (PCB) und Organochlorpestizide im Sediment der Ostsee und der Küsten-gew?sser Mecklenburg-Vorpommerns

Zusammenfassung Die Verteilungen von polychlorierten Biphenylen (PCB) und Organochlorpestiziden (DDT, HCH und HCB) wurden in Oberfl?chensedimenten (0–2 cm) und in Sedimentkernen (0–45 cm) der westlichen Ostsee und der Küstengew?sser Mecklenburg-Vorpommerns untersucht. Die Sedimentprobenahme erfolgte in der Beltsee, der Arkonasee, der Pommerschen Bucht und in nahezu allen Bodden-und Haffgew?ssern Mecklenburg-Vorpommerns im Herbst 1994 und 1995. Die h?chsten Konzentrationen wurden für die PCB-und DDT-Verbindungen bis 214 ng g^-1 Trockenmasse (TM) in den Küstengew?ssern gemessen. Für die HCH-Isomeren lagen die Werte zwischen 0,01 und 2,9 ng g^-1 TM, mit h?chsten Konzentrationen für das Β-HCH. Die Werte der chlorierten Kohlenwasserstoffe (CKW) variieren nach der Sedimentbeschaffenheit und weisen auf erh?hte Eintr?ge über die Flu\systeme (Oder und Peene) hin. Die h?heren Konzentrationen in den Bodden-und Haffgew?ssern charakterisieren diese Gebiete als Senke und durch erneute Mobilisierung der oberen Sedimentschicht in das Pelagial auch als Quelle für die organischen Schadstoffe. Insbesondere konnten die Eintr?ge aus der Landwirtschaft und aus industriellen Punktquellen (Werftstandorte, Schiffbau) in den Küstengew?ssern festgestellt werden. Die nahezu homogene PCB-und DDT-Verteilung im Oberfl?chensediment der westlichen Ostsee ist ein Hinweis auf die hohe Sedimentdynamik in diesem Gebiet. Dieses wird durch die Ergebnisse der Untersuchungen an Sedimentkernen unterstützt, die eine konstante PCB-und DDT-Verteilung bis zu einer Tiefe von 15 bis 20 cm zeigten.