The Amazon river breeze and the local boundary layer: I. Observations

Observations of the diurnal evolution of the planetary boundary layer over the Amazon rain forest, made at sites close to the confluence of the Solimões and Negro rivers (approximately at 3°S, 60°W) near Manaus, Amazonas, Brazil, show the existence of a diurnal rotation of the wind near the surface and the frequent presence of low-level nocturnal wind maxima. These circulations are shown to be plausibly explained as elements of a river and land breeze circulation induced by the thermal contrast between the rivers and the adjacent forest.     

Precipitation variability during the past 400?years in the Xiaolong Mountain (central China) inferred from tree rings

We developed the first tree-ring chronology, based on 73 cores from 29 Pinus tabulaeformis trees, for the Xiaolong Mountain area of central China, a region at the boundary of the Asian summer monsoon. This chronology exhibits significant (at 0.01 level) positive correlations with precipitation in May and June, and negative correlations with temperature in May, June and July. Highest linear correlation is observed between tree growth and the seasonalized (April–July) precipitation, suggesting that tree rings tend to integrate the monthly precipitation signals. Accordingly, the April–July total precipitation was reconstructed back to 1629 using these tree rings, explaining 44.7?% of the instrumental variance. A severe drought occurred in the area during the 1630s–1640s, which may be related to the weakened Asian summer monsoon caused by a low land-sea thermal gradient. The dry epoch during the 1920s–1930s and since the late 1970s may be explained by the strengthened Hadley circulation in a warmer climate. The dry (wet) epochs of the 1920s–1930s (the 1750s and 1950s) occurred during the warm (cold) phases of the El Ni?o-Southern Oscillation and the Pacific Decadal Oscillation that are often associated with weakened (strengthened) East Asian summer monsoon. These relationships indicate significant teleconnections operating over the past centuries in central China related to large-scale synoptic features.     

平湖油气田凝析油回注油藏对开发效果影响机理研究

凝析油回注油藏是平湖油气田开发过程中为应对海底输油管线而采取的一种工程应急措施。凝析油回注油藏会引起油层内流体渗流特征的变化，并进而影响油井恢复生产后的开发指标。从室内物理模拟实验和油藏数值模拟两方面开展凝析油回注油藏的影响效果分析，并根据研究结果提出合理的回注方式，不仅从机理上为解决海上油气田开发工程中所遇类似突发事件的处理提供了依据，而且在物理模拟实验和油藏数值模拟研究相结合对油藏基础研究方面提供一些重要的结论。     

Can Plant Competition and Diversity Reduce the Growth and Survival of Exotic <Emphasis Type="Italic">Phragmites australis</Emphasis> Invading a Tidal Marsh?

The rapid proliferation of Phragmites australis in North America has challenged resource managers to curb its expansion and reduce the loss of functional tidal marsh. We investigated whether native plant competition could reduce the ability of Phragmites to invade a tidal marsh, and if plant diversity (species richness, evenness, and composition) altered the competitive outcome. Immature Phragmites shoots and four native halophytes were transplanted to small but dense field plots (~1,200 shoots m⁻²) comprising three community structure types (Phragmites alone, Phragmites + 1 native species, and Phragmites + 4 native species). Interspecific competition significantly reduced Phragmites aboveground biomass, shoot length production, density, and survival by approximately 60%. Additionally, plots planted with greater native diversity contained Phragmites with the lowest growth and survival, potentially indicating diversity-enhanced resource competition. Competition consistently reduced the growth of Phragmites even under favorable conditions: lack of strong tidal flooding stresses as well as elevated nutrient pools.     

Water level variations in the Neuse and Pamlico Estuaries,North Carolina due to local and remote forcing

Water level time series records from the Neuse and Pamlico River Estuaries were statistically compared to local and distant wind field data, water level records within the Pamlico Sound and also coastal ocean sites to determine the relative contribution of each time series to water levels in the Neuse and Pamlico Estuaries. The objectives of this study were to examine these time series data using various statistical methods (i.e. autoregressive, empirical orthogonal function analysis (EOF), exploratory data analysis (EDA)) to determine short- and long-time-scale variability, and to develop predictive statistical models that can be used to estimate past water level fluctuations in both the Neuse Estuary (NE) and Pamlico Estuary (PE). Short- and long-time-scale similarities were observed in all time series of estuarine, Pamlico Sound and subtidal coastal ocean water level and wind component data, due to events (nor'easters, fronts and tropical systems) and seasonality. Empirical orthogonal function analyses revealed a strong coastal ocean and wind field contribution to water level in the NE and PE. Approximately 95% of the variation was captured in the first two EOF components for water level data from the NE, sound and coastal ocean, and 70% for the PE, sound and coastal ocean. Spectral density plots revealed strong diurnal signals in both wind and water level data, and a strong cross correlation and coherency between the NE water level and the North/South wind component. There was good agreement between data and predictions using autoregressive statistical models for the NE (R² = 0.92) and PE (R² = 0.76). These methods also revealed significant autoregressive lags for the NE (days 1 and 3) and for the PE (days 1, 2 and 3). Significant departures from predictions are attributed to local meteorological and hydrological events. The autoregressive techniques showed significant predictive improvement over ordinary least squares methods. The results are considered within the context of providing long time-scale hindcast data for the two estuaries, and the importance of these data for multidisciplinary researchers and managers.     

A Case Study on the Effects of Heterogeneous Soil Moisture on Mesoscale Boundary-Layer Structure in the Southern Great Plains, U.S.A. Part II: Mesoscale Modelling

The importance of soil moisture inputs and improved model physics in the prediction of the daytime boundary-layer structure during the Southern Great Plains Hydrology Experiment 1997 (SGP97) is investigated using the non-hydrostatic fifth-generation Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model MM5. This is Part II of a two-part study examining the relationship of surface heterogeneity to observed boundary-layer structure. Part I focuses on observations and utilizes a simple model while Part II uses observations and MM5 modelling. Soil moisture inputs tested include a lookup table based on soil type and season, output from an offline land-surface model (LSM) forced by atmospheric observations, and high-resolution ( 800 m) airborne microwave remotely sensed data. Model physics improvements are investigated by comparing an LSM directly coupled with the MM5 to a simpler force-restore method at the surface. The scale of land surface heterogeneities is compared to the scale of their effects on boundary-layer structure.The use of more detailed soil moisture fields allowed the MM5 to better represent the large-scale (hundreds of km) and small-scale (tens of km) horizontal gradients in surface-layer weather and, to a lesser degree, the atmospheric boundary-layer (ABL) height, which was evaluated against observations measured by differential absorption lidar (DIAL). The benefits of coupling an LSM to the MM5 were not readily evident in this summertime case, with the model having particular difficulty simulating the timing of maximum surface fluxes while underestimating the depth of the mixed layer.     

Marymia: an Archean, amphibolite facies-hosted, orogenic lode-gold deposit overprinted by Palaeoproterozoic orogenesis and base metal mineralisation, Western Australia

The Marymia gold deposit, comprising two orebodies, Keillor 1 and Keillor 2, is at the northern end of the Plutonic Well greenstone belt in the Marymia Inlier, in the southern Capricorn Orogen, just north of the Yilgarn craton. The Marymia Inlier is a discrete fault-bounded Archean gneiss-granitoid-greenstone domain surrounded by sedimentary basins that were formed and variably metamorphosed and deformed during several Palaeoproterozoic orogenic cycles. The greenstone sequence at Marymia is stratigraphically and geochemically similar to greenstone sequences in the Yilgarn craton, but was subjected to further deformation and metamorphism in the Palaeoproterozoic. Late Archean deformation (D1-D2) was ductile to brittle-ductile in style, whereas Palaeoproterozoic deformation was predominantly brittle. Equilibrium mineral assemblages indicate that peak amphibolite-facies metamorphism (540-575 °C, <3 kb) was overprinted by greenschist-facies metamorphism (300-360 °C). Petrographic textures indicate that prograde metamorphism was coeval with D1-D2, with peak metamorphism early to syn D2. Gold mineralisation at Marymia is hosted in metamorphosed tholeiitic basalts and banded iron formation. On a gross scale, the distribution of gold is controlled by D2 folds and shear zones. Lithological contacts with strong rheological or chemical contrasts provide local controls. Gold-related alteration comprises subtle millimetre- to centimetre-wide zones of silicification with variable amounts of quartz, hornblende, biotite, K-feldspar, plagioclase, calcite/siderite, scheelite, titanite, epidote, sulfide and telluride minerals. Quartz veins are generally narrow and discontinuous with low total volume of quartz. Gold is sited in the wall rock, at vein salvedges or within stringers of wall rock within veins. There are two distinct opaque-mineral assemblages: pyrite-pyrrhotite-chalcopyrite-galena and hessite-petzite-altaite-Bi-telluride-galena. Ore samples are variably enriched in Ag, Te, Pb, W, Cu, S and Fe reflecting heterogeneity of the ore mineralogy. Structural timing and temperature of formation of alteration and ore minerals support deposition of gold during late peak amphibolite-facies metamorphism from neutral to alkaline (pH=5-6), moderately oxidising (log P_O2,-21-22) and CO₂-bearing (X_CO2 Ƹ.2) fluids. The total sulfur content of the fluid is estimated at 1mDS. Lead isotope compositions support derivation of lead from within the local greenstone sequence. Gold lodes were deformed by faults and shear zones in the Palaeoproterozoic, with only limited remobilisation. Subeconomic, carbonate vein- and breccia-hosted base metal mineralisation is locally hosted within Palaeoproterozoic fault zones, which clearly cut gold lodes. Base-metal-related alteration is characterised by intense carbonatisation, chloritisation, and albitisation of the mafic host rocks. Mineral assemblages are consistent with formation at greenschist facies conditions. Lead isotope compositions support crystallisation at ca. 1.7 Ga from lead that is similar in composition to earlier gold-related galena.     

Stellar polarization and the structure of the magnetic field of our galaxy

The stellar polarization data have been examined using a new catalogue containing accurate stellar distances. On the assumption of a magnetic alignment hypothesis, correlations on the larger distance scale indicate the existence of a dominant regular magnetic field, although its characteristics are difficult to determine. Within 500 pc its direction is towardsl45° and beyond this towardsl60°, though it is clear that such a longitudinal model is too simple. There is also some evidence for an inclination of this field to the galactic plane. The distribution of the polarization vectors away from the galactic plane has been examined and it is proposed that the two largest loop structures, previously identified as Supernova remnants, are linked by the regular field. Incremental polarization maps have been produced but they show little correlation with the spiral structure. The polarization appears to be saturated at about 1 kpc from the Sun, which is explained as the result of an observational selection effect. On the smaller distance scales an autocorrelation analysis in different directions has revealed no obvious coherence in the irregular component on scales greater than 50 pc.