Recent temperature and precipitation increases in West Siberia and their association with the Arctic Oscillation

Surface air temperature and precipitation records for the years 1958-1999 from ten meteorological stations located throughout West Siberia are used to identify climatic trends and determine to what extent these trends are potentially attributable to the Arctic Oscillation (AO). Although recent changes in atmospheric variability are associated with broad Arctic climate change, West Siberia appears particularly susceptible to warming. Furthermore, unlike most of the Arctic, moisture transport in the region is highly variable. The records show that West Siberia is experiencing significant warming and notable increases in precipitation, likely driven, in part, by large-scale Arctic atmospheric variability. Because this region contains a large percentage of the world's peatlands and contributes a significant portion of the total terrestrial freshwater flux to the Arctic Ocean, these recent climatic trends may have globally significant repercussions. The most robust patterns found are strong and prevalent springtime warming, winter precipitation increases, and strong association of non-summer air temperatures with the AO. Warming rates for both spring (0.5-0.8 °C/decade) and annual (0.3-0.5°C/decade) records are statistically significant for nine often stations. On average, the AO is linearly congruent with 96% (winter), 19% (spring), 0% (summer), 67% (autumn) and 53% (annual) of the warming found in this study. Significant trends in precipitation occur most commonly during winter, when four of ten stations exhibit significant increases (4-13 %/decade). The AO may play a lesser role in precipitation variability and is linearly congruent with only 17% (winter), 13% (spring), 12% (summer), 1% (autumn) and 26% (annual) of precipitation trends.     

A GIS based planning support system for assessing financial feasibility of urban redevelopment

Urban densification trends combined with redevelopment increasingly moving away from large former industrial and transport sites toward existing town centres and corridors indicate redevelopment is becoming increasingly complex, difficult to plan for and undertake. The interplay between land and property markets and planning frameworks suggest city planners and urban researchers need new tools and methodologies to gain insights into ways to deliver effective responses. Despite the need, there is a limited availability of comprehensive models to fulfil the task. This paper describes a GIS-based tool to assess parcel-level financial feasibility and housing supply associated with urban redevelopment within a precinct. The tool incorporates existing and potential built form and parameters associated with the planning framework and land and property markets. Using a real case study in a workshop, tool performance was evaluated by professional urban planners in terms of its capacity to produce metrics and visualisations of potential scenarios of redevelopment. Results indicate the usefulness of the tool for emulating land market conditions and testing scenarios of planning regulation and market changes for strategic planning purposes.     

Nutrient flux into an intense deep chlorophyll layer in a mode-water eddy

An intense deep chlorophyll layer in the Sargasso Sea was reported near the center of an anticyclonic mode-water eddy by McGillicuddy et al. [2007. Eddy–wind interactions stimulate extraordinary mid-ocean plankton blooms, Science, accepted]. The high chlorophyll was associated with anomalously high concentrations of diatoms and with a maximum in the vertical profile of ¹⁴C primary productivity. Here we report tracer measurements of the vertical advection and turbulent diffusion of deep-water nutrients into this chlorophyll layer. Tracer released in the chlorophyll layer revealed upward motion relative to isopycnal surfaces of about 0.4 m/d, due to solar heating and mixing. The density surfaces themselves shoaled by about 0.1 m/d. The upward flux of dissolved inorganic nitrogen, averaged over 36 days, was approximately 0.6 mmol/m²/d due to both upwelling and mixing. This flux is about 40% of the basin wide, annually averaged, nitrogen flux required to drive the annual new production in the Sargasso Sea, estimated from the oxygen cycle in the euphotic zone, the oxygen demand below the euphotic zone, and from the ³He excess in the mixed layer. The observed upwelling of the fluid was consistent with theoretical models [Dewar, W.K., Flierl, G.R., 1987. Some effects of wind on rings. Journal of Physical Oceanography 17, 1653–1667; Martin, A.P., Richards, K.J., 2001. Mechanisms for vertical nutrient transport within a North Atlantic mesoscale eddy. Deep-Sea Research II 48, 757–773] in which eddy surface currents cause spatial variations in surface stress. The diapycnal diffusivity at the base of the euphotic zone was 3.5±0.5×10⁻⁵ m²/s. Diapycnal mixing was probably enhanced over more typical values by the series of storms passing over the eddy during the experiment and may have been enhanced further by the trapping of near-inertial waves generated within the eddy.     

Review of self-potential methods in hydrogeophysics

The self-potential (SP) method is a passive geophysical method based on the natural occurrence of electrical fields on the Earth's surface. Combined with other geophysical methods, SP surveys are especially useful for localizing and quantifying groundwater flows and pollutant plume spreading, and estimating pertinent hydraulic properties of aquifers (water table, hydraulic conductivity). Laboratory experiments have shown that the involved coupling coefficients mainly depend on the fluid chemistry, conductivity and pH, and on the soil or rock properties. The interpretation of SP observations can be done qualitatively, for instance, by correlation of SP gradients with water fluxes (through electrokinetics) or salt fluxes (through electro-diffusion). In recent years, the interpretation has been improved with the help of modelling or/and inversion of the Poisson equation and endeavours to estimate hydraulic parameters by means of the intensity of electric current sources caused by underground flows.     

The reliability of analytical data for tributyltin (TBT) in sea water and its implications on water quality criteria

To investigate the reliability of analytical data for tributyltin (TBT) in sea water, split water samples were distributed to ten laboratories in six countries. The sub-surface samples comprised: (i) an offshore (0·5 km) water sample, (ii) the same sample but spiked with an undisclosed quantity of TBT standard compound (175 ng TBT⁺ liter⁻¹), and (iii) a sample taken from a yacht marina. The seven acceptable data sets were in good agreement for the spiked sample (178 ± 26 ng TBT⁺ liter⁻¹) but showed a greater variation in concentrations reported for the yacht marina sample (366 ± 93 ng TBT⁺ liter⁻¹). Atomic absorption and gas chromatographic-flame photometric detection techniques produced results of similar accuracy and precision. Samples acidified with 1 ml of 10% (v/v) acetic acid appeared stable for more than 2 weeks when stored refrigerated and in darkness. Analyses of the offshore seawater sample revealed TBT contamination (9 ± 7 ng TBT⁺ liter⁻¹) indicating dispersion of the compound to the shelf waters off Monaco. The spread in values reported by the laboratories demonstrates inherent difficulties in obtaining good precision below approximately 20 ng TBT⁺ liter⁻¹. This observation is discussed with respect to the setting and enforcing of water quality standards.     

Ion winds in Saturn's southern auroral/polar region

We present profiles of the line-of-sight (l.o.s.) ionospheric wind velocities in the southern auroral/polar region of Saturn. Our velocities are derived from the measurement of Doppler shifting of the H₃⁺ν₂Q(1,0⁻) line at 3.953 microns. The data for this study were obtained using the facility high-resolution spectrometer CSHELL on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, during the night of February 6, 2003 (UT). The l.o.s. velocity profiles finally derived are consistent with an extended region of the upper atmosphere sub-corotating with the planet: the ion velocities in the inertial reference are only 1/3 of those expected for full planetary corotation. We discuss the results in the light of recent proposals for the kronian magnetosphere, and suggest that, in this region, Saturn's ion winds may be under solar wind control.     

Multi-wavelength simulations of atmospheric radiation from Io with a 3-D spherical-shell backward Monte Carlo radiative transfer model

Conflicting observations regarding the dominance of either sublimation or volcanism as the source of the atmosphere on Io and disparate reports on the extent of its spatial distribution and the absolute column abundance invite the development of detailed computational models capable of improving our understanding of Io’s unique atmospheric structure and origin. Improving upon previous models, Walker et al. (Walker, A.C., Gratiy, S.L., Levin, D.A., Goldstein, D.B., Varghese, P.L., Trafton, L.M., Moore, C.H., Stewart, B. [2009]. Icarus) developed a fully 3-D global rarefied gas dynamics model of Io’s atmosphere including both sublimation and volcanic sources of SO₂ gas. The fidelity of the model is tested by simulating remote observations at selected wavelength bands and comparing them to the corresponding astronomical observations of Io’s atmosphere. The simulations are performed with a new 3-D spherical-shell radiative transfer code utilizing a backward Monte Carlo method. We present: (1) simulations of the mid-infrared disk-integrated spectra of Io’s sunlit hemisphere at 19 μm, obtained with TEXES during 2001-2004; (2) simulations of disk-resolved images at Lyman-α obtained with the Hubble Space Telescope (HST), Space Telescope Imaging Spectrograph (STIS) during 1997-2001; and (3) disk-integrated simulations of emission line profiles in the millimeter wavelength range obtained with the IRAM-30 m telescope in October-November 1999. We found that the atmospheric model generally reproduces the longitudinal variation in band depth from the mid-infrared data; however, the best match is obtained when our simulation results are shifted ∼30° toward lower orbital longitudes. The simulations of Lyman-α images do not reproduce the mid-to-high latitude bright patches seen in the observations, suggesting that the model atmosphere sustains columns that are too high at those latitudes. The simulations of emission line profiles in the millimeter spectral region support the hypothesis that the atmospheric dynamics favorably explains the observed line widths, which are too wide to be formed by thermal Doppler broadening alone.