Homogeneity assessment of a station climate series (1933–2005) in the Metropolitan Area of S?o Paulo: instruments change and urbanization effects

This work assessed homogeneity of the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) weather station climate series, using various statistical techniques. The record from this target station is one of the longest in Brazil, having commenced in 1933 with observations of precipitation, and temperatures and other variables later in 1936. Thus, it is one of the few stations in Brazil with enough data for long-term climate variability and climate change studies. There is, however, a possibility that its data may have been contaminated by some artifacts over time. Admittedly, there was an intervention on the observations in 1958, with the replacement of instruments, for which the size of impact has not been yet evaluated. The station transformed in the course of time from rural to urban, and this may also have influenced homogeneity of the observations and makes the station less representative for climate studies over larger spatial scales. Homogeneity of the target station was assessed applying both absolute, or single station tests, and tests relatively to regional climate, in annual scale, regarding daily precipitation, relative humidity, maximum (TMax), minimum (TMin), and wet bulb temperatures. Among these quantities, only precipitation does not exhibit any inhomogeneity. A clear signal of change of instruments in 1958 was detected in the TMax and relative humidity data, the latter certainly because of its strong dependence on temperature. This signal is not very clear in TMin, but it presents non-climatic discontinuities around 1953 and around 1970. A significant homogeneity break is found around 1990 for TMax and wet bulb temperature. The discontinuities detected after 1958 may have been caused by urbanization, as the observed warming trend in the station is considerably greater than that corresponding to regional climate.     

The role of aluminium in the preservation of microbial biosignatures

Demonstrating the biogenicity of presumptive microfossils in the geological record often requires supporting chemical signatures, including isotopic signatures. Understanding the mechanisms that promote the preservation of microbial biosignatures associated with microfossils is fundamental to unravelling the palaeomicrobiological history of the material. Organomineralization of microorganisms is likely to represent the first stages of microbial fossilisation and has been hypothesised to prevent the autolytic degradation of microbial cell envelope structures. In the present study, two distinct fossilisation textures(permineralised microfossils and iron oxide encrusted cell envelopes)identified throughout iron-rich rock samples were analysed using nanoscale secondary ion mass spectrometry(NanoSIMS). In this system, aluminium is enriched around the permineralised microfossils, while iron is enriched within the intracellularly, within distinct cell envelopes. Remarkably,while cell wall structures are indicated, carbon and nitrogen biosignatures are not preserved with permineralised microfossils. Therefore, the enrichment of aluminium, delineating these microfossils appears to have been critical to their structural preservation in this iron-rich environment. In contrast,NanoSIMS analysis of mineral encrusted cell envelopes reveals that preserved carbon and nitrogen biosignatures are associated with the cell envelope structures of these microfossils. Interestingly, iron is depleted in regions where carbon and nitrogen are preserved. In contrast aluminium appears to be slightly enriched in regions associated with remnant cell envelope structures. The correlation of aluminium with carbon and nitrogen biosignatures suggests the complexation of aluminium with preserved cell envelope structures before or immediately after cell death may have inactivated autolytic activity preventing the rapid breakdown of these organic, macromolecular structures.Combined, these results highlight that aluminium may play an important role in the preservation of microorganisms within the rock record.     

The spatial and seasonal variation of trace metals in coastal seawater and soft tissue of <Emphasis Type="Italic">Chthamalus montagui</Emphasis> around the northwest coast of Portugal

Metal concentrations (Cd, Cr, Cu, Fe, Mn and Zn) were determined in seawaters and soft tissues of Chthamalus montagui from the northwest coast of Portugal during the four seasons of 2011. The main objectives of this work were to assess seasonal and spatial variations of metals in order to detect hot spots of contamination, to establish correlations between metals in coastal seawaters and C. montagui and to calculate metal bioaccumulation factors (BAFs) in each season. Metal concentrations in coastal seawaters ranged within Cd: 1.2–35 ng L^?1; Cr: 15–87 ng L^?1; Mn: 77–1763 ng L^?1; Cu: 126–1819 ng L^?1; Fe: 430–4048 ng L^?1 and Zn: 2889–16867 ng L^?1 and in C. montagui ranged for Cd: 0.39–1.98 mg kg^?1; Cr: 0.45–3.13 mg kg^?1; Cu: 0.93–5.70 mg kg^?1; Mn: 2.2–20.4 mg kg^?1; Fe: 135–707 mg kg^?1 and Zn: 119–782 mg kg^?1. Significant spatial and seasonal variations were found between: (i) metal concentrations in seawaters and C. montagui tissues; (ii) the distribution of metal concentrations in C. montagui tissues were Fe > Zn > Mn > Cu > Cr > Cd and (iii) C. montagui showed higher bioaccumulation factors for Fe and Cd than for Cu, Mn and Zn in all seasons. Regarding the metal concentrations accumulated in C. montagui tissues during each season of 2011, the ecological quality classifications of the NW coast of Portugal varied from “Class I–Unpolluted” to “Class III–Remarkably Polluted”.     

Estimates of effective permeability for non-Newtonian fluid flow in randomly heterogeneous porous media

An understanding of the interplay between non-Newtonian effects in porous media flow and field-scale domain heterogeneity is of great importance in several engineering and geological applications. Here we present a simplified approach to the derivation of an effective permeability for flow of a purely viscous power–law fluid with flow behavior index n in a randomly heterogeneous porous domain subject to a uniform pressure gradient. A standard form of the flow law generalizing the Darcy’s law to non-Newtonian fluids is adopted, with the permeability coefficient being the only source of randomness. The natural logarithm of the permeability is considered a spatially homogeneous and correlated Gaussian random field. Under the ergodic hypothesis, an effective permeability is first derived for two limit 1-D flow geometries: flow parallel to permeability variation (serial-type layers), and flow transverse to permeability variation (parallel-type layers). The effective permeability of a 2-D or 3-D isotropic domain is conjectured to be a power average of 1-D results, generalizing results valid for Newtonian fluids under the validity of Darcy’s law; the conjecture is validated comparing our results with previous literature findings. The conjecture is then extended, allowing the exponents of the power averaging to be functions of the flow behavior index. For Newtonian flow, novel expressions for the effective permeability reduce to those derived in the past. The effective permeability is shown to be a function of flow dimensionality, domain heterogeneity, and flow behavior index. The impact of heterogeneity is significant, especially for shear-thinning fluids with a low flow behavior index, which tend to exhibit channeling behavior.     

Occurrence and distribution of vibrios in fishes and shellfishes in coastal waters of Hong Kong

INTRODUCTIONTheoccurrenceanddistributionofhalophilicvibriosinthecoastalwatersofHongKonghasbeenrePorted(Chanetal.,l986).Theresultsshowedthatvibrioswerepresentduringthesum-mermonthsinHongKongcoastalwatersatconcentrationsof9oto67ooind./cm3,accountingo.4l%~4o%ofthetotalbacterialPOpulationofthe48isolatesexaminedindetail.Theyob-servedV.Paraheamolyticus,V.harvha,V.vulnfficus,V.camPbelliandV.fiuvialis.Becausemanyofthevibri0species,includingsome0ftheisolatesbyChanetal.(1986)fromHongKongwate…     

The effect of an arctic polynya on the Northern Hemisphere mean circulation and eddy regime: a numerical experiment

The feedback of an arctic polynya, which is a large ice-free zone within the sea ice, on the hemispheric climate is studied with the ECMWF T21 GCM. For this purpose a control and an anomaly integration, in which a polynya was introduced in the Kara Sea, are compared. As the GCM, like the real atmosphere, shows a high level of low frequency variability, the mean response to the changed boundary conditions is obscured by internal noise. The necessary significance analyses are thus performed to enhance the signal-tonoise ratio within the framework of an a priori chosen guess pattern and a multivariate test statistic. The sensible and latent heat fluxes increased above the polynya, which resulted in a warming of the lower troposphere above and near the polynya. No statistically significant local or global sea-level pressure changes are associated with this heating. However we find a significant change of hemispheric extent of the geopotential fields at 300 hPa, if we use as guess patterns the eigenmodes of the barotropic vorticity equation. The different mean flow field is accompanied by significant changes of the synoptic transient eddy field. We find a significant variation in the barotropic and baroclinic forcing of the mean flow by the eddies, a change in the location and intensity of the storm tracks and in the conversion between eddy available and eddy kinetic energy. The additional heat flux from the polynya results in a reduction of the meridional heat flux by the synoptic eddies on the western Atlantic.     

Composition and origin of nodules from the ≈20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma — Vesuvius, Italy

Nodules (coarse-grain ??plutonic?? rocks) were collected from the ca. 20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma-Vesuvius, Italy. The nodules are classified as monzonite-monzogabbro based on their modal composition. The nodules have porphyrogranular texture, and consist of An-rich plagioclase, K-feldspar, clinopyroxene (ferroan-diopside), mica (phlogopite-biotite) ± olivine and amphibole. Aggregates of irregular intergrowths of mostly alkali feldspar and plagioclase, along with mica, Fe-Ti-oxides and clinopyroxene, in the nodules are interpreted as crystallized melt pockets. Crystallized silicate melt inclusions (MI) are common in the nodules, especially in clinopyroxenes. Two types of MI have been identified. Type I consists of mica, Fe-Ti-oxides and/or dark green spinel, clinopyroxene, feldspar and a vapor bubble. Volatiles (CO₂, H₂O) could not be detected in the vapor bubbles by Raman spectroscopy. Type II inclusions are generally lighter in color and contain subhedral feldspar and/or glass and several opaque phases, most of which are confirmed to be oxide minerals by SEM analysis. Some of the opaque-appearing phases that are below the surface may be tiny vapor bubbles. The two types of MI have different chemical compositions. Type I MI are classified as phono-tephrite ?? tephri-phonolite ?? basaltic trachy-andesite, while Type II MI have basaltic composition. The petrography and MI geochemistry led us to conclude that the nodules represent samples of the crystal mush zone in the active plumbing system of Mt. Somma-Vesuvius that were entrained into the upwelling magma during the PB-Sarno eruption.     

Northern hemisphere atmospheric response to changes of atlantic ocean SST on decadal time scales: a GCM experiment

Analyses indicate that the Atlantic Ocean seasurface temperature (SST) was considerably colder at the beginning than in the middle of the century. In parallel, a systematic change in the North Atlantic sea-level pressure (SLP) pattern was observed. To find out whether the SST and SLP changes analyzed are consistent, which would indicate that the SST change was real and not an instrumental artifact, a response experiment with a low-resolution (T21) atmospheric GCM was performed. Two perpetual January simulations were conducted, which differ solely in the Atlantic Ocean (40° S-60° N) SST: the cold simulation utilizes the SSTs for the period 1904–1913; the warm simulation uses the SSTs for the period 1951–1960. Also, a control run with the model's standard SST somewhat between the cold and warm SST was made. For the response analysis, a rigorous statistical approach was taken. First, the null hypothesis of identical horizontal distributions was subjected to a multivariate significance test. Second, the level of recurrence was estimated. The multivariate statistical approaches are based on hierarchies of test models. We examined three different hierarchies: a scale-dependent hierarchy based on spherical harmonics (S), and two physically motivated ones, one based on the barotropic normal modes of the mean 300 hPa flow (B) and one based on the eigenmodes of the advection diffusion operator at 1000 hPa (A). The intercomparison of the cold and warm experiments indicates a signal in the geostrophic stream function that in the S-hierarchy is significantly nonzero and highly recurrent. In the A-hierarchy, the low level temperature field is identified as being significantly and recurrently affected by the altered SST distribution. The SLP signal is reasonably similar to the SLP change observed. Unexpectedly, the upper level stream-function signal does not appear to be significantly nonzero in the B-hierarchy. If, however, the pairs of experiments warm versus control and cold versus control are examined in the B-hierarchy, a highly significant and recurrent signal emerges. We conclude that the cold versus warm response is not a small disturbance that would allow the signal to be described by eigenmodes of the linear system. An analysis of the three-dimensional structure of the signal leads to the hypothesis that two different mechanisms are acting to modify the model's mean state. At low levels, local heating and advection are dominant, but at upper levels the extratropical signal is a remote responce to modifications of the tropical convection.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute for Meteorology. Guest Editor for these papers is Dr. L. Dilmenil.AWI Publication no. 254     

Observations concerning the relationship between the quiet-time ring current and electron temperatures at trough latitudes

The relationship between the simultaneously observed positions of the maximum omnidirectional flux of the quiet-time ring current positive ions (Λ_φ) and the maximum electron temperature Λ_T in the trough is studied in the midnight sector of the topside ionosphere. Λ_φ maps to the inner edge of the plasma sheet where ring current fluxes change from nearly isotropic to trapped. At altitudes near 2500 km, the electron temperature at trough latitudes were always sharply peaked. Although Λ_φ varied with the level of geomagnetic activity, (Λ_φ ? Λ_T) did not. These observations support the hypothesis that the quiet-time ring current is the source of elevated electron temperatures found near the plasmapause. Below 1300 km, peaked electron temperature distributions in the trough were not consistent features of the data. It is shown that (Λ_φ ? Λ_T) increased with decreasing altitude. The possible influences of a westward component to the convective electric field and ionospheric refraction of ion cyclotron waves are discussed.     

New estimations of precipitation and surface sublimation in East Antarctica from snow accumulation measurements

Surface mass balance (SMB) distribution and its temporal and spatial variability is an essential input parameter in mass balance studies. Different methods were used, compared and integrated (stake farms, ice cores, snow radar, surface morphology, remote sensing) at eight sites along a transect from Terra Nova Bay (TNB) to Dome C (DC) (East Antarctica), to provide detailed information on the SMB. Spatial variability measurements show that the measured maximum snow accumulation (SA) in a 15 km area is well correlated to firn temperature. Wind-driven sublimation processes, controlled by the surface slope in the wind direction, have a huge impact (up to 85% of snow precipitation) on SMB and are significant in terms of past, present and future SMB evaluations. The snow redistribution process is local and has a strong impact on the annual variability of accumulation. The spatial variability of SMB at the kilometre scale is one order of magnitude higher than its temporal variability (20–30%) at the centennial time scale. This high spatial variability is due to wind-driven sublimation. Compared with our SMB calculations, previous compilations generally over-estimate SMB, up to 65% in some areas.