An aircraft study of turbulence dissipation rate and temperature structure function in the unstable marine atmospheric boundary layer

The dissipation rate of turbulent kinetic energy, , and the temperature structure function parameter, C _T ², have been measured over water from the near surface (Z = 3 m) to the top of the boundary layer. The near surface values of and C _T ² were used to calculate the velocity and temperature Monin-Obukhov scaling parameters u _* and T _*. The data collected during unstable lapse rates were used to evaluate the feasibility of extrapolating the values of and C _T ² as a function of height with empirical scaling formulae. The dissipation rate scaling formula of Wyngaard et al. (l971 a) gave a good fit to an average of the data for Z < 0.8 Z _i. In the surface layer the scaling formula of Wyngaard et al. (1971b) disagreed with the C _T ² values by as much as 50%. This disagreement is due to an unexpected reduction in the measured values of C _T ² forZ < 30 m. At this point it is not clear if the discrepancy is a unique property of the marine boundary layer or if it is simply some unknown instrumental or analytical problem. The mixed layer scaling results were similar to the overland results of Kaimal et al. (1976).     

Measurements of the humidity structure function parameters,C q 2and C Tq,over the ocean

Atmospheric turbulence measurements, including temperature and humidity fluctuations, were made from the R/V Acania off the coast of California in June, 1979. The purpose of the experiment was to investigate the scaling properties of the humidity structure function parameter (C _q ²) and temperaturehumidity cospectrum structure parameter (C _Tq) in the marine surface layer. The bulk parameterization method was used to obtain Monin-Obukhov Similarity (MOS) scaling parameters u _*, T _*, q _*and L. Assuming a neutral stability humidity drag coefficient c _qn = 1.3 × 10^-3the dimensionless humidity structure function parameter C _q ²Z^2/3/q_* ²was found to be 18% lower than the corresponding temperature function obtained by Wyngaard et al. (1971). Furthermore, the measurements indicate that the temperature-humidity fluctuations are highly coherent well into the inertial subrange. The results have direct application to turbulent scattering of waves propagating in the atmosphere (particularly microwaves) and methods of estimating air-sea surface fluxes.     

Observation of the temperature structure function parameter,C T 2, over the ocean

Shipboard measurements of temperature fluctuations, mean wind, temperature, and humidity permit comparisons to be made of experimental and empirical estimates of c_t ², the temperature structure function parameter. Surface flux estimates are obtained from bulk aerodynamic formulae. Temperature fluctuation data are selected to minimize a salt-contamination effect which causes increases in temperature variance. Predictions for C_T ² based on surface flux scaling agree within 20%, except for near neutral and large unstable conditions where disagreement can be attributed to measurement problems.     

Chlorinated cooling waters in the marine environment: Development of effluent guidelines

The effects of free chlorine and chloramine on stage I lobster larvae and juvenile killifish were investigated in continuous flow bioassay units. In comparing mortality and changes in standard respiration rates during and after exposure to either chlorine form, significant respiratory stress was observed with exposure to sublethal levels. Sublethal responses to free and combined chlorine should be considered when establishing regulations for chlorine residuals in cooling waters.     

Geochemical and Sr–O isotopic constraints on magmatic differentiation at Gede Volcanic Complex, West Java, Indonesia

The Gede Volcanic Complex (GVC) of the Sunda island arc (West Java, Indonesia) consists of multiple volcanic centres and eruptive groups with complex magmatic histories. We present new petrological, mineralogical, whole-rock major and trace element and Sr–O isotopic data to provide constraints on the relative importance of fractional crystallisation and magma mixing in petrogenesis, as well as on the role and nature of the arc crust. Banded juvenile scoria from Young and Old Gede provide unequivocal evidence for the (late-stage) interaction of distinct magmas at Gede volcano. However, the relatively small-degree compositional zoning observed in plagioclase phenocrysts of all eruptive groups (up to ~20 mol% An) may be attributed to physical changes in magma properties (e.g. P, T, and PH₂O) rather than changes in melt composition. Major element and trace element variations within each eruptive series are inconsistent with magmatic evolution through simple mixing processes. Instead, mixing of variably fractionated magma batches is suggested to account for the significant scatter in some element variation diagrams. No correlation is observed between textural complexity and/or mineral disequilibrium and whole-rock geochemistry. REE data and geochemical modelling indicate that fractional crystallisation involving amphibole in the mid- to lower crust, and fractionation of plagioclase, clinopyroxene, Fe–Ti oxide ± olivine ± orthopyroxene provide strong control on the geochemical evolution of GVC rocks. Two-pyroxene geothermobarometry provides pre-eruption crystallisation temperatures of 891–1,046°C and pressures of 3.4–6.5 kbar, equivalent to ~13–24 km depth beneath the volcanoes (mid- to lower crust). Low, mantle-like clinopyroxene δ¹⁸O values of GVC lavas and poor correlation of Sr isotope ratios with indices of differentiation precludes significant assimilation of isotopically distinct crust during magmatic differentiation. Therefore, we suggest that the geochemical character of the moderately thick West Javan arc crust is relatively immature compared to typical continental crust. Trace element ratios and strontium isotopes show that the magmatic source composition of the older geographical units, Gegerbentang and Older Quaternary, is distinct from the other GVC groups.     

Resource allocation for regional earthquake risk mitigation: a case study of Tehran,Iran

This paper presents a new optimization model to help cities in seismically active developing countries decide (1) How much to spend on pre-earthquake mitigation versus waiting until after an event and paying for reconstruction or simply not rebuilding damaged buildings? (2) Which buildings to mitigate and how? and (3) Which buildings to reconstruct and how? It extends previously developed optimization models to consider the particular issues that arise in such countries. First, the model allows for the possibility that some damaged buildings will not be reconstructed immediately and keeps track of any lost building inventory. Second, buildings can be mitigated to, or when damaged, reconstructed to, any appropriate structural type and seismic design level. Finally, the model objectives include minimizing the chance of an extremely high death toll in any one earthquake and minimizing the average annual death toll across earthquakes. The model is illustrated through a case study analysis for Tehran, Iran.     

A simple numerical model for inlet sedimentation at intermittently open–closed coastal lagoons

This contribution aims to model the dominant processes that control sedimentation within the ocean inlet to intermittently open–closed coastal lagoons; focussing on the role of infilling, backfilling and morphodynamic feedback. The key elements that have been included in the present model are: (1) the delivery of sediment to the mouth of the estuary by littoral processes; (2) sediment transport processes within the inlet due to non-linear tidal flow; and (3) the down-slope diffusion of sediment. The model discussed here includes a simple one-dimensional (1-D), non-linear flow parameterisation that predicts the spatial variability in the magnitude and non-linearity of the tidal flow. The predicted third and fourth velocity moments are used to drive a morphodynamic module. Down-slope diffusion of sediment is dealt with in a separate diffusion term in the bed-evolution equation. Feedback between the evolving morphology and the flow field are integral to the model. Numerical simulations are used to investigate different modes of evolution for this type of inlet system. Inlet closure due to infilling is critically controlled by the balance between sediment addition at the mouth due to littoral processes and the removal of sediment by non-linear tidal flow. Rapid widening or deepening of the inlet at its landward margin leads to the deposition of a flood shoal. Under conditions of high sedimentation (and low diffusion) the flood shoal can become sufficiently well developed to present a physical barrier to sediment entering the lagoon. Under these circumstances backfilling can become significant. The infilling and backfilling processes are ameliorated by efficient down-slope diffusion which is controlled in the present model by a diffusion parameter, D. High diffusion coefficients slow inlet closure and allow sediment to propagate further into the lagoon.     

Excitation of Sr ii lines in Eta Carinae

We study the nature of the peculiar [Sr  ii ] and Sr  ii emission filament found in the ejecta of Eta Carinae. To this purpose we carry out ab initio calculations of radiative transition probabilities and electron impact excitation rate coefficients for Sr  ii . Then we build a multilevel model for the system which is used to investigate the physical condition of the filament and the nature of the observed allowed and forbidden Sr  ii optical emission. It is found that the observed spectrum is consistent with the lines being pumped by the continuum radiation field in a mostly neutral region with electron density near 10⁷ cm⁻³. Under these conditions, the observed emission can be explained without the need for a large Sr overabundance.