Influence of surface heterogeneity on scalar dissimilarity in the roughness sublayer

While it is generally known that surface heterogeneity weakens the application of Monin–Obukhov similarity (MOS), few studies have investigated how seasonal changes in the degree of surface heterogeneity at a particular site may influence the validity of the similarity application. Exploiting seasonal changes in forest function associated with senescence, we conduct a unique evaluation of the effects of surface heterogeneity on the validity of similarity theory at two sites through time. Using high frequency (10 Hz) velocity and scalar time series collected within the roughness sublayer over mixed hardwood deciduous and coniferous forests during both periods of peak leaf area and senescence of deciduous foliage, we examined conformity with proposed universal flux-variance predictions and agreement amongst normalized standard deviations of different scalars (temperature, water vapour and carbon dioxide concentrations). Normalized scalar standard deviations were elevated above MOS flux-variance predictions, with more pronounced deviations observed during and following senescence, particularly in the case of CO₂. Power-law scaling of normalized standard deviations as a function of stability was upheld and robust to seasonal changes in surface heterogeneity. However, dissimilarity of normalized standard deviations for the scalars increased during senescence, as heterogeneity in the source/sink field increased. Scalewise decomposition of scalar time series using wavelet analysis indicated that correlations between scalars were conservative through much of the inertial cascade but decayed for eddies < 10 m. Senescence lowered correlations between scalars over a wide range of eddy sizes. These results demonstrate how seasonal changes in surface physiology can cause a temporal production of heterogeneity in the source/sink field, thus weakening similarity applications in the roughness sublayer.     

Comprehensive Evaluation of Fast-Response,Reynolds-Averaged Navier–Stokes,and Large-Eddy Simulation Methods Against High-Spatial-Resolution Wind-Tunnel Data in Step-Down Street Canyons

Three computational fluid dynamics (CFD) methods with different levels of flow-physics modelling are comprehensively evaluated against high-spatial-resolution wind-tunnel velocity data from step-down street canyons (i.e., a short building downwind of a tall building). The first method is a semi-empirical fast-response approach using the Quick Urban Industrial Complex (QUIC-URB) model. The second method solves the Reynolds-averaged Navier–Stokes (RANS) equations, and the third one utilizes a fully-coupled fluid-structure interaction large-eddy simulation (LES) model with a grid-turbulence inflow generator. Unlike typical point-by-point evaluation comparisons, here the entire two-dimensional wind-tunnel dataset is used to evaluate the dynamics of dominant flow topological features in the street canyon. Each CFD method is scrutinized for several geometric configurations by varying the downwind-to-upwind building-height ratio (\(H_\mathrm{d}/H_\mathrm{u}\)) and street canyon-width to building-width aspect ratio (S / W) for inflow winds perpendicular to the upwind building front face. Disparities between the numerical results and experimental data are quantified in terms of their ability to capture flow topological features for different geometric configurations. Overall, all three methods qualitatively predict the primary flow topological features, including a saddle point and a primary vortex. However, the secondary flow topological features, namely an in-canyon separation point and secondary vortices, are only well represented by the LES method despite its failure for taller downwind building cases. Misrepresentation of flow-regime transitions, exaggeration of the coherence of recirculation zones and wake fields, and overestimation of downwards vertical velocity into the canyon are the main defects in QUIC-URB, RANS and LES results, respectively. All three methods underestimate the updrafts and, surprisingly, QUIC-URB outperforms RANS for the streamwise velocity component, while RANS is superior to QUIC-URB for the vertical velocity component in the street canyon.     

Evaluation of surface wind and flux analysis techniques using conventional data in marine cyclones

Data from seven storms from the Storm Transfer and Response Experiment in November 1980 have been used to evaluate the relative accuracy of surface wind and flux fields based on two analysis procedures. Two essentially independent techniques were used; objective analysis which is based on composite data taken at several synoptic intervals to enhance the number of observations and processing carefully hand-analyzed (subjective) surface pressure analyses into wind and flux fields using a planetary boundary layer (PBL) similarity model. Scale and accuracy limits imposed by instrument accuracy, sampling error, and gridding and analysis procedures are evaluated for each of these techniques by comparison with independent data and with each other.Wind field differences between the objective composite analysis and the PBL model predictions are found to be comparable to the measurement-related uncertainty in the observations. Unresolved variability in the 10–100 km scale of the dynamic and thermodynamic variables produces the main source of error in both the objective and model wind fields. Additional wind field differences are contributed by PBL and gradient wind assumptions used in the PBL model. Wind differences between either of the two analyses and individual observations are about ±3 m s⁻¹ and ±30° in the mean, and can be greater than ±5 m s⁻¹ and ±50° for small regions. Comparable differences are found between the two wind field analyses.The wind and thermodynamic field differences combine to produce substantial differences in the derived fields. Mean differences of ±19W m⁻² and ±41 W m⁻² for the fluxes of sensible and latent heat, respectively, represent differences of about 50% of the mean fluxes, with local differences as much as double or triple the magnitude of these means. Fronts are equally well represented by the two analyses, but values of divergence and curl of surface stress may differ by a factor of 2 or more in regions of fronts. These local differences in the derived fields result primarily from the large wind field differences in these inadequately resolved regions.     

The application of a segmented tidal mixing model to the Great Bay Estuary,N.H.

Measurements show that in general salt is vertically well-mixed everywhere in the Great Bay Estuary, New Hampshire except near the river entrances at the head of the estuary. Dyer and Taylor’s (1973) modified version of Ketchum’s segmented tidal prism model has been applied to the Great Bay Estuarine System in order to predict high and low water salinity distribution for a specified river flow. The theory has been modified here to account for the mixing which occurs at the junction of two branches of an estuary. The mixing parameter, which in this model is related to the tidal excursion of water in the estuary, has been determined for different segments in the estuary on the basis of a comparison between predictions and a comprehensive data set obtained for a low river flow period. Using a mixing parameter distribution based on the low river flow calibration procedure the salinity distribution has been predicted for high river flow. The resulting salinity distribution compares favorably with observations for most of the estuary. The corresponding flushing times for water parcels entering at the head of the estuary during periods of low and high river flow is 54.5 and 45.9 tidal cycles respectively.     

Comparison of Bio-P module and the Modified Bio-P module in the step-feed biological nutrient removal process

The Modified Bio-P module was evaluated in terms of the kinetic rate expression and engineering parameters, comparing the measured data of full-scale plant with simulated data. To simulate step-feed BNR (Biological Nutrient Removal), the ASM3 (Activated Sludge Model 3) with the EAWAG Bio-P Module (The Swiss Federal Institute for Environmental Science and Technology) and the ASM3+Modified Bio-P module were used. The RMSEs (root mean square error) of the T-N (total nitrogen) concentration of the effluent levels of measured and simulated examples were 2.29 for ASM3+Bio-P and 1.28 for ASM3+Modified Bio-P. In the case of T-P (total phosphorus), the RMSEs were 0.28 for ASM3+Bio-P and 0.25 for ASM3+Modified Bio-P. The annual removal rates for T-N were 0.77 for the measured, 0.69 for the Bio-P, and 0.74 for the Modified Bio-P samples, while the annual removal rates for T-P were 0.64 for the measured, 0.72 for the Bio-P, and 0.60 for the Modified Bio-P cases. With simulated data, the Modified Bio-P model was a better fit for the field data compared to Bio-P. The Modified Bio-P module reproduced the step-feed process more effectively than the Bio-P module.     

Partitioning of Hf,Lu, Ti,and Mn between olivine,clinopyroxene and basaltic liquid

The crystal/liquid partition coefficients of Lu, Hf, Ti, Mn and Ca have been measured between olivine, clinopyroxene and basaltic melt. The Ti, Mn, and Ca partition coefficients were determined at natural abundance levels. The Lu and Hf partition coefficients were determined at doping levels ranging from 0.5 to 1.5 wt% “trace element” as oxide in order to allow analysis by electron microprobe. Olivine/liquid partition coefficients for Lu, Hf, Ti, Mn, and Ca were determined at 1 bar and temperatures from 1150 to 1177° C. Clinopyroxene/liquid partition coefficients were determined for Lu, Hf, Ti, and Mn at pressures of 10, 15, and 20 kbars and temperatures from 1250 to 1290° C. The olivine/liquid partition coefficients of Hf, Lu, Ti, and Ca are small. D(Hf-ol) is zero within the analytical uncertainty. Both D(Lu-ol) and D(Mn-ol) decrease with increasing temperature, but D(Ti-ol) and D(Ca-ol) are constant over the narrow temperature range studied. The partition coefficient results are summarized below.

Observations on the relevance of the industrial-Urban hypothesis for rural development

Rural development tends to be viewed as a facet of urban development in the sense that rural areas are expected to be recipients of positive urban spill-overs. To that end, two concepts have been formulated: growth centre theory and the Industrial-Urban Hypothesis (IUH). The former has been beset by conceptual problems whereas the simpler IUH has not been tested in a Canadian context. This paper tests the basic IUH proposition that the general level of rural development is an inverse function of urban accessibility. Findings suggest that the IUH is more attuned to the impacts of smaller centres rather than the region's metropolitan centre. However, introduction of an exogenous element based on ethnic variations in rural settlements indicate how socializing factors work to modify the IUH concept.     

A Mass Balance Model that Uses Low-altitude Meteorological Observations and the Area–Altitude Distribution of a Glacier

A glacier mass balance model that requires only low-altitude precipitation and temperature observations and the glacier's areaaltitude distribution is presented as an alternative to direct field measurements. Input to the model for South Cascade Glacier are daily weather observations at stations 30–60 km from the glacier and at altitudes 1300 to 1500 m lower than the glacier. The model relies on the internal consistency of mass balance variables that are generated by simulation using the low-altitude weather data. The daily values of such balance variables as snowline altitude, zero balance altitude, glacier balance, balance flux and the accumulation area ratio are correlated throughout the ablation season using two-degree polynomial regressions to obtain the lowest fitting error. When the minimum average error (or maximum R ²) is attained, the generated balances and other variables are considered to be real. A simplex optimization technique is used to determine the optimal coefficient values that are used in algorithms to convert meteorological observations to snow accumulation and snow and ice ablation. The independently produced simulation results for the 1959–1996 period are compared with balances measured at the glacier. The agreement between annual balances for individual years is fair and between long-term volume changes measured by the geodetic method is excellent.     

Dissolved iodine in waters overlying and in the Orca Basin,Gulf of Mexico

The distribution and speciation of iodine, a biophilic redox-sensitive trace element, in waters overlying and in the Orca Basin, Gulf of Mexico, which contains hypersaline, anoxic and yet non-sulfide-bearing brine have been determined. The distribution of iodate and iodide in the oxic waters overlying the anoxic brine are similar to those reported in other oceans. However, in the oxic-anoxic mixing zone, iodate disappears while the concentration of iodide reaches a maximum of 8.1 μM, the highest concentration ever reported in open oceans. There is also a maximum in specific iodine of 30.7 nM‰^?1 at this depth. Specific iodine in oxic seawater is only about 10–14 nM ‰^?1. These features may be explained by the preferential dissolution of biogenic particles that have accumulated in a strong pycnocline. In the anoxic brine proper, the concentration of iodide is 3.8 μM and can be explained almost entirely by the simultaneous mobilization of chloride and iodide during the dissolution of evaporite beds as the specific iodine of 14.5 nM‰^?1 is only slightly higher than those observed in the oxic waters.     

Subtidal Marine Algal Community and Endangered Species in Dokdo and Ulleungdo,Two Oceanic Islands in the East Sea of Korea

Ocean Science Journal - Dokdo and Ulleungdo islands harbor diverse marine algae and are therefore uniquely well-suited for research on marine algae distribution and ecological changes. However,...