Large-scale Zones Research Articles

The quasi-periodic behavior of rainfall variability in Africa and its relationship to the southern oscillation

The temporal characteristics of rainfall variability in Africa are examined using departure series for 84 regions of the continent and five larger-scale zones. The forms of non-randomness which are investigated include linear trends, persistence and quasi-periodic fluctuations. No long-term trends in African rainfall are evident. In some sectors, most noteably along the Benguela coast and equatorial Africa, rainfall anomalies tend to persist over several months and interseasonal correlations are also high. Spectral analysis revealed significant quasi-periodicities clustered in four bands at 2.2–2.4, 2.6–2.8, 3.3–3.8 and 5.0–6.3 years. These are common throughout equatorial and southern Africa, but only weakly evident in northern Africa. A cross-spectral analysis with the Southern Oscillation suggests a strong influence on rainfall variability in southern Africa and parts of the equatorial region and minimal influence in northern Africa. Coherence with the Southern Oscillation is particularly strong in the QBO range of 2.2–2.4 years. In general, the co-spectra suggest an inverse relationship between the SOI and rainfall in equatorial regions (i.e., higher rainfall during low-index years) and a positive relationship with rainfall in most other regions where an influence can be demonstrated.

FEEDING REQUIREMENTS OF KRILL IN RELATION TO FOOD SOURCES

ABSTRACT During the Melville expedition to the Scotia Sea January-March 1981, a multidisciplinary team of investigators studied the distribution and biomass of Euphausia superba, addition to its food resources. The areas studied included five north-south transects of the Scotia Sea (33°–50°W) where krill were relatively sparse, and an area north of Elephant Island where a superswarm of krill was encountered. Krill biomass, determined on samples obtained by paired bongo nets (1 m2), has been used to calculate the minimal daily food requirements for all stages of krill from Calyptopis I to the adult stage. The mean krill biomass the upper 200 m of the water column the Scotia Sea (10.6 mg dry weight m–3) would require 0.105–-0.211 mg C m–3 d–1; the corresponding value for krill the swarm area (270 mg dry weight m–3) was 2.4-5.4 mg C m–3 d-'. The phytoplankton productivity for the upper 200 m the Scotia Sea and the swarm area was estimated to be 4.8 and 4.2 mg C m–3 d-', respectively. Our calculations have been concerned mainly with the minimal daily carbon requirements for maintenance metabolism. Data of other investigators have been used to compare the total carbon requirement for growth of krill on a seasonal basis. In areas of dense krill aggregations (such as that north of Elephant Island) our calculations indicate that phytoplankton productivity can sustain maintenance metabolism by the krill population, but may not provide for full growth of the individuals. Other factors must be invoked here, such as dispersal of the swarm, horizontal movements of the krill along lines of increasing food concentrations, and advection of food resources into the swarm area. Floristic analyses of phytoplankton in and out of krill swarms suggest that the krill preferentially consume the larger phytoplankton, and leave most of the nannoplankton. Our data from the Scotia Sea indicate that this area is very high primary production as compared to most other sections of the Antarctic Ocean, and this might be responsible for the high krill biomass reported for this area. The BIOMASS acoustic data set indicates, however, that the greatest krill concentrations exist the East Indian Ocean (61 mg dry weight m–3), where data indicate that primary production is very low. This anomaly requires further investigation on the relationship of large-scale zones of high primary production Antarctic waters and their relation to zooplankton biomass.

Regional Fracture Analysis in Western Valley and Ridge and Adjoining Plateau, West Virginia and Maryland: ABSTRACT

Approximately 2,500 stations were occupied for joint analysis in the western Valley and Ridge and eastern Allegheny Plateau of West Virginia and Maryland. Structural positions range from the Georges Creek-Stony River syncline atop the Allegheny Plateau to the Nittany anticlinorium and western Broad Top synclinorium in the Valley and Ridge. Rocks exposed range in age from Middle Ordovician carbonate within the core of the Wills Mountain anticline to Pennsylvanian coal measures on the Allegheny Plateau. The highest percentage of joint readings was obtained from Middle to Upper Devonian sandstone, siltstones, and shales because of the widespread areal distribution of these rocks within the Bedford and Clearville synclines. Here, fracture trends are similar to those observed n Devonian shale cores taken farther west. As many as eight different joint sets are present within the study area although only four to five major systematic sets are pervasive throughout the entire region. Most commonly only two, or at the most three, joint sets are present at the scale of the individual outcrop. Consideration of joint crosscutting and offset relationships, tendential and transient features, fibrous mineralization, stylolites, and slickenlines has permitted the establishment of a consistent chronology of joint development throughout the region. Joint set I (N30°to 50°W) formed first as extension fractures early in the lithification history of all formations, followed by a less commonly developed orthogonal set trending N40° to 60°E. Both sets predated Alleghenian folding. Fracture plume d ta indicate upward propagation for joint development, perhaps associated with regional northeastward extension into the deepest part of the Paleozoic depositional basin. Joint set II (N55° to 70°W) formed second in response to early Alleghenian compressive stress, coupled with continuous subsidence, before folding. Locally, minor and nonregionally pervasive fractures showing shear joint geometry also developed at this time. Joint set III (N20° to 30°E) formed as extension fractures parallel to fold axes, with fracture inception early in fold development. Joint set IV (N75°E to N75°W) shows slickenlines more commonly than other sets and formed late in the folding history, possibly as shear joints where structures were effectively locked. More likely this se formed as extension joints in response to post-folding stresses, perhaps consistent with the present-day regional stress field. A moderately to poorly developed joint set V (N10°E to N10°W) formed last in the region as an orthogonal set to IV. The dominant joint set or sets at any location within the study area depend on the bedding thicknesses, lithology, structural position, and early fracture history. Prediction for joint trends, and possible hydrocarbon migration timing at depth in potential fractured reservoirs, must consider this aspect as well as chronological development, especially in view of the different stress fields within lower and upper thin-skinned plates. The study did not reveal large-scale zones of high joint frequency except for the confirmation of increased fracturing in linear belts such as the Petersburg lineament and Parsons lineament previously reported by Sites, Dixon, Wheeler and Dixon, and Wilson. End_of_Article - Last_Page 448------------

停滞したリッジ西縁の亜熱帯レインバンド

The largeand meso-scale features of a subtropical rainband which caused thunderstorms over western Japan (-33N/130E) in 25-7 July 1981 are studied. This case aroused our interest because the convective activities persisted for about three days in the west side of a slowmoving ridge.Radar observations showed a persistent convective echo band of -800km length extending in NNW-SSE direction. This echo band was not accompanied with front-like strong thermal gradient. Satellite IR imageries showed that the rainband was a part of a long subtropical cloud zone formed along the northern periphery of the extremely moist tropical maritime airmass in the lower troposphere. The enhancement of cloud zone and the formation of the rainband was owing to the incessant feeding of moisture accompanied with the northward intrusion of the moist tropical maritime air along the western hem of the slow- moving ridge.Real data forecast experiments on the cloud zone and rainband were made using a coarseand a fine-mesh primitive equation model. While only the large-scale zone of weak precipitation relevant to the observed cloud zone was produced in the coarse-mesh (380kmmesh) model, the narrow rainband with low-level convergence was simulated in the finemesh (77km-mesh) model. The "dry experiment" (a experiment without condensation) did not produce any low-level convergence zone. This indicated influence of condensation process on the formation of this subtropical rainband.

A Vertical Pattern of Variation in the St. Peter Sandstone--Fourier Grain Shape Analysis

ABSTRACT Fourier grain shape analysis of quartz sand grains from a vertical section of the St. Peter Sandstone at St. Paul, Minn., has detected a vertical pattern of non-random variation in the relative proportions of 2 shape families. The shape families consist of mature, highly abraded sand, and irregularly shaped, immature, sand respectively. Changes in the proportion of mature and irregular sands define large-scale (7, 19 foot) zones characterized by a decrease upwards in irregular sand content, and within each zone smaller scaled units of interbedded mature and irregular sands which form cycles approximately 1 foot thick. In light of studies of Recent shelf environments (Brown and Ehrlich, 1980) the large-scale zones are interpreted as a record of individual transgressive phases with a resultant movement of the littoral energy fence (and concomittantly the shoreline) away from the area. Two and, perhaps, three such zones occur in the uppermost 30 feet studied. If their repetition is due to regressive pulses, this corroborates Sloss' (1963) observations that the middle Ordovician transgression was interrupted by numerous partial regressions. The small-scale cycles within each zone are interpreted to record the breaching of the littoral energy fence; each thin layer of irregular sand is likely storm-generated. Detection of such a detailed record in an otherwise homogeneous, featureless orthoquartzite ind cates that the Fourier grain shape technique, applied on a regional scale to the St. Peter Sandstone, may reveal a clearer record of its accumulation.

Purification and Properties of Whale Thyroid-stimulating Hormone<subtitle>II. Isolation of Multiple Components</subtitle>

In view of the finding that whale thyroid-stimulating hormone (TSH) contains at least four biologically active components with different isoelectric points (2), attempts were made to purify these four components in a homogeneous state. Crude preparations of whale TSH obtained by acetone precipitation were purified by large-scale zone electrophoresis, and the TSH-rich fraction thus prepared was fractionated by isoelectric focusing into four components having the isoelectric point at pH 8.1, 8.3, 8.5 and 8.7, respectively. These fractions still showed the presence of two bands in disc electrophoresis; only the faster band had TSH activity. Each fraction of TSH obtained by isoelectric focusing was subjected to chromatography on TEAE-cellulose to remove the slower-migrating protein, and further purified by gel filtration on Sephadex G-100. These highly active preparations (TSH I–IV) were found to be homogeneous in disc electrophoresis, immunodiffusion and immunoelectrophoresis, except for one preparation which showed signs of the presence of a small amount of contaminant in immunoelectrophoresis. The slower-migrating component in each TSH fraction obtained by isoelectric focusing was also purified. These preparations, which gave a single band in disc electrophoresis, showed a strong luteinizing hormone (LH) activity comparable to that reported for purified LH from other species.

Structural factors in metasomatism related to endogenic mineral deposits of Middle Asia and the Urals

Skarn formation, high-temperature mineralization of carbonate rocks, lower-temperature localization in large-scale faults and breccia zones, USSR