Interpolation de variables régionales et cartographie automatique: modèle triangulaire hydrologique (MTH) / Interpolation of regional variables and automatic drawing of isoplets

Abstract

The degree of relationship between hydrological variables being independent of time series properties is especially related to the distance between gauging stations of these variables. The linear character of these variables without extreme deviation in time makes possible the use of a new method of interpolation. Following is an explanation of a method which generalizes methods of linear interpolation of two points. Computing the variable values at each point, automatic drawing of isoplets and the water height in a basin can be easily computed by this method.     

Spillway design floods in Sweden: I. New guidelines

Abstract

The new Swedish guidelines for the estimation of design floods for dams and spillways are presented, with emphasis on high-hazard dams. The method is based on a set of regional design precipitation sequences, rescaled for basin area, season and elevation above sea level, and a full hydrological model. A reservoir operation strategy is also a fundamental component of the guidelines. The most critical combination of flood generating factors is searched by systematically inserting the design precipitation sequence into a ten year climatological record, where the initial snowpack has been replaced by a statistical 30-year snowpack. The new guidelines are applicable to single reservoir systems as well as more complex hydroelectric schemes, and cover snowmelt floods, rain floods and combinations of the two. In order to study the probabilities of the computed floods and to avoid regional inconsistencies, extensive comparisons with observed floods and frequency analyses have been carried out.     

Social–ecological memory in urban gardens—Retaining the capacity for management of ecosystem services

Many ecosystem services are in decline. Local ecological knowledge and associated practice are essential to sustain and enhance ecosystem services on the ground. Here, we focus on social or collective memory in relation to management practice that sustains ecosystem services, and investigate where and how ecological practices, knowledge and experience are retained and transmitted. We analyze such social–ecological memory of allotment gardens in the Stockholm urban area, Sweden. Allotment gardens support ecosystem services such as pollination, seed dispersal and pest regulation in the broader urban landscape. Surveys and interviews were preformed over a four-year period with several hundreds of gardeners. We found that the allotment gardens function as communities-of-practice, where participation and reification interact and social–ecological memory is a shared source of resilience of the community by being both emergent and persistent. Ecological practices and knowledge in allotment gardens are retained and transmitted by imitation of practices, oral communication and collective rituals and habits, as well as by the physical gardens, artifacts, metaphors and rules-in-use (institutions). Finally, a wider social context provides external support through various forms of media, markets, social networks, collaborative organizations, and legal structures. We exemplify the role of urban gardens in generating ecosystem services in times of crisis and change and conclude that stewards of urban green areas and the social memory that they carry may help counteract further decline of critical ecosystem services.     

Young pumice deposits on Nisyros,Greece

The island of Nisyros (Aegean Sea) consists of a silicic volcanic sequence upon a base of mafic-andesitic hyaloclastites, lava flows, and breccias. We distinguish two young silicic eruptive cycles each consisting of an explosive phase followed by effusions, and an older silicic complex with major pyroclastic deposits. The caldera that formed after the last plinian eruption is partially filled with dacitic domes. Each of the two youngest plinian pumice falls has an approximate DRE volume of 2–3 km³ and calculated eruption column heights of about 15–20 km. The youngest pumice unit is a fall-surge-flow-surge sequence. Laterally transitional fall and surge facies, as well as distinct polymodal grainsize distributions in the basal fall layer, indicate coeval deposition from a maintained plume and surges. Planar-bedded pumice units on top of the fall layer were deposited from high-energy, dry-steam propelled surges and grade laterally into cross-bedded, finegrained surge deposits. The change from a fall-to a surge/flow-dominated depositional regime coincided with a trend from low-temperature argillitic lithics to high-temperature, epidote-and diopside-bearing lithic clasts, indicating the break-up of a high-temperature geothermal reservoir after the plinian phase. The transition from a maintained plume to a surge/ash flow depositional regime occurred most likely during break-up of the high-temperature geothermal reservoir during chaotic caldera collapse. The upper surge units were possibly erupted through the newly formed ringfracture.     

The Černý Důl deposit (Czechoslovakia): An example of Ni-, Fe-, Ag-, Cu-arsenide mineralization with extremely high activity of arsenic; new data on paxite,novakite and kutinaite

Summary The erný Dl mineralization (Giant Mts., Czechoslovakia) consists of calcite veins cross-cutting metamorphic rocks and exhibiting a complex paragenesis of Ni-, Fe-, (Co)- and Cu-, Ag-arsenides associated with native arsenic. Several new minerals belonging to Cu–As and Cu–Ag–As systems were described from this deposit (koutekite, novakite, paxite, kutinaite). New data on paxite, novakite and kutinaite were obtained. Paxite, CuAs₂, is monoclinic,P2₁/c,a=5.830,b=5.111,c=8.084 Å, =99.7°,Z=4,D _calc=5.97 g/cm³, polysynthetically twinned along (010). Novakite belongs to the Cu–Ag–As system. It is monoclinic,C2/m,Cm orC2,a=16.269,b=11.711,c=10.007 Å, -112.7°,Z=4,D _calc=8.01 g/cm³. The ideal formula is Cu_20+x Ag_1–x As₁₀,x0.16. New microprobe analyses of kutinaite indicate a cell-content of 4 [Cu₁₄Ag₆As₇],D _calc=8.37 g/cm³.

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Résumé La minéralisation du gisement de erný Dl (Monts des Géants, Tchécoslovaquie) se distingue par une paragenèse complexe d'arséniures de Ni, Fe, (Co), Cu et Ag associés à l'arsenic natif, et apparaissant dans des filons de calcite qui recoupent une série de roches métamorphiques. Plusieurs minéraux nouveaux appartenant aux systèmes Cu–As et Cu–Ag–As ont été découverts dans ce gisement (koutekite, novakite, paxite, kutinaïte). De nouvelles données sur la paxite, la novakite et la kutinaïte ont été obtenues. La paxite, CuAs₂, est monoclinique,P2₁/c,a=5,830,b=5,111,c=8,084 Å, =99,7°,Z=4,D _calc=5,97 g/cm³; elle est polysythétiquement maclée suivant (010). La novakite est une phase du système Cu–Ag–As. Elle est monoclinique,C2/m,Cm ouC2,a=16,269,b=11,711,c=10,007 Å, =112,7°,Z=4,D _calc=8,01 g/cm³. Saformule idéale s'écrit Cu_20+x Ag_1–x As₁₀,x0,16. Des analyses de la kutinaïte conduisent à 4 [Cu₁₄Ag₆As₇] par maille,D _calc=8,37 g/cm³.L'étude paragénétique a permis de voir que le système hydrothermal à erný Dl couvre un interval de température large, s'étalant de500° à 100°C environ. Une très forte activité d'arsenic au cours des épisodes minéralisants tardifs a abouti à la cristallisation des arséniures de Cu riches en arsenic, stables à basse température. Cinq épisodes minéralisants ont été reconnus: le dépôt des arséniures de Ni, Fe, (Co) (löllingite, nickéline, pararammelsbergite, chloentite) était suivi de: kutinaïte, koutekite, arsenic natif et arséniures de cuivre riches en arsenic (novakite, Cu₂As, paxite). L'abondance des carbonates laisse entrevoir un rôle de composés ou de complexes de carbone dans l'évolution de ce système hydrothermal fortement réducteur.The study of mineral associations showed that the erný Dl hydrothermal system extended over a large temperature interval from 500° to 100°C. An extremely high arsenic activity during the late mineralization periods lead to the precipitation of low-temperature, As-rich copper arsenides. Five mineralization periods were distinguished: the precipitation of Ni-, Fe-, (Co)-arsenides (löllingite, nickeline, pararammelsbergite, chloanthite) was followed by kutinaite, koutekite, native arsenic and As-rich copper arsenides (novakite, Cu₂As, paxite). The abundance of carbonates suggests a possible role of carbon compounds or complexes in the evolution of this highly reducing hydrothermal system.

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With 2 Figures     

Boundary-layer ozone depletion as seen in the Norwegian Arctic in spring

Several years of measurements of ozone, hydrocarbons, sulphate and meteorological parameters from Spitsbergen in the Norwegian Arctic are presented. Most of the measurements were taken on the Zeppelin Mountain at an altitude of 474 m a.s.l. The focus is the episodes of ozone depletion in the lower troposphere in spring, which are studied in a climatological way. Episodes of very low ozone concentrations are a common feature on the Zeppelin Mountain in spring. The low ozone episodes were observed from late March to the beginning of June. When the effect of transport direction was subtracted, the frequenty of the low ozone episodes was found to peak in the beginning of May, possibly reflecting the seasonal cycle in the actual depletion process. Analyses based on trajectory calculations show that most of the episodes occurred when the air masses were transported from W-N. Ozone soundings show that the ozone depletion may extend from the surface and up to 3–4 km altitude. The episodes were associated with a cold boundary layer beneath a thermally stable layer, suppressing mixing with the free troposphere. The concentration of several individual hydrocarbons was much lower during episodes of low ozone than for the average conditions. The change in concentration ratio between the hydrocarbons was in qualitative agreement with oxidation of hydrocarbons by Br and Cl atoms rather than by OH radicals.     

Effect of Aftershocks on Earthquake Hazard Estimation: An Example from the North Anatolian Fault Zone

In order to investigate the effect of aftershocks on earthquake hazard estimation, earthquake hazard parameters (_m, b and M_max) have been estimated by the maximum likelihood method from the main shocks catalogue and the raw earthquakes catalogue for the North Anatolian Fault Zone (NAFZ). The main shocks catalogue has been compiled from the raw earthquake catalogue by eliminating the aftershocks using the window method. The raw earthquake catalogue consisted of instrumentally detected earthquakes between 1900 and 1992, and historical earthquakes that occurred between 1000–1900. For the events of the mainshock catalogue the Poisson process is valid and for the raw earthquake catalogue it does not fit. The paper demonstrates differences in the hazard outputs if on one hand the main catalogues and on the other hand the raw catalogue is used. The maximum likelihood method which allows the use of the mixed earthquake catalogue containing incomplete (historical) and complete (instrumental) earthquake data is used to determine the earthquake hazard parameters. The maximum regional magnitude (M_max, the seismic activity rate (_m), the mean return period (R) and the b value of the magnitude-frequency relation have been estimated for the 24°–31° E, 31°–41° E, 41°–45° E sections of the North Anatolian Fault Zone from the raw earthquake catalogue and the main shocks catalogue. Our results indicate that inclusion of aftershocks changes the b value and the seismic activity rate _m depending on the proportion of aftershocks in a region while it does not significantly effect the value of the maximum regional magnitude since it is related to the maximum observed magnitude. These changes in the earthquake hazard parameters caused the return periods to be over- and underestimated for smaller and larger events, respectively.     

North-south asymmetries in the green corona brightness between 1947 and 1976

The north-south asymmetry has been studied using the green emission corona brightness in the period of 1947–1976. (N - S)/(N + S) values are constructed with the 5-deg opposite coronal belts brightnesses between ± 5 and ± 60 deg. Power spectra analyses were performed to study periodicities of these (N - S)/(N + S) values. Two noticeable periodicities (14.5 and 5 yr) have been found.     

On some flare-sensitive high photospheric and low chromospheric lines

During a stay at the Kitt Peak National Observatory the writer has tried to find an influence of flare radiation on the high photospheric and low chromospheric lines of the area occupied by the flare. Observations have been made in the H region and in the region of the H and K lines. When flare emission is present in sunspots some of the faint (molecular) lines seem to be weakened. When a flare appears near the solar limb some of the Evershed-type (chromospheric) lines are strongly influenced.Kitt Peak National Observatory Contribution No. 481.Visiting Astronomer to the Solar Division, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.