An analysis of heat-, momentum-transports,and spectra for clear air turbulence in mid-stratosphere

Summary An analysis of the clear air turbulence in the mid-stratosphere indicates that the turbulence is characterized by an anisotropic field of turbulence with an intense lateral component of the turbulence, associated with strong thermally stable stratification. The Richardson number in the region of turbulence is generally smaller than , the Taylor's criterion for a stratified shear flow.The cospectra for the momentum transport by the streamwise, lateral, and vertical components of the velocity show similarity in their distribution, decreasing with increasing wavenumber. The cospectra for the heat transport by the streamwise, lateral, and vertical components of the velocity show similarity in the high and medium wavenumber ranges, but not in the low wavenumber range of the spectra.The power spectra of the temperature and wind speed are very similar, and are approximately proportional to the power of the wavenumber. The power spectra of the streamwise and lateral components of the velocity are approximately proportional to the –2 power of the wavenumber, whereas the spectrum of the vertical component of the velocity is approximately proportional to the –1 power of the wavenumber.sponsored by the National Science Foundation.     

A numerical study of the nocturnal heat island over a medium-sized mid-latitude city (Columbus,Ohio)

A numerical investigation is conducted of the nocturnal heat island over Columbus, Ohio, a relatively flat mid-latitude city. Specifically, a cross-sectional steady-state numerical model to simulate the (thermal) structure of the nocturnal urban boundary layer is developed from a one-dimensional, time-dependent model due to Estoque. The model is applied to Columbus for special periods in September 1968 and March 1969 during which comparable experimental data were collected. The numerical simulations agree well with the observed data with respect to the detailed spatial form of the surface-based thermal boundary layer across the city. The use of the model for other metropolitan areas, for ascertaining the relative effect of city size and building geometry on the development of the thermal boundary layer, and for determining the effect of alternate land-use strategies on the thermal stratification are also discussed.Digest of portion of a dissertation submitted to the Pennsylvania State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.Presented in part at the Air Pollution, Turbulence and Diffusion Symposium, Las Cruces, New Mexico, 7–10 December 1971.On assignment from the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.     

Amino acids in the Murchison meteorite

Continued investigation of the Murchison meteorite by gas chromatography combined with mass spectrometry has led to the characterization of at least 17 amino acids in addition to the 18 identified in earlier work. The total population consists of a wide variety of linear and cyclic difunctional and polyfunctional amino acids, of which the linear difunctional amino acids show a general decrease in concentration as the number of carbon atoms in the amino acid molecule increases. These results are consistent with the hypothesis that the amino acids are present as the result of an extraterrestrial, abiotic synthesis.     

Subsurface electric fields of a grounded cable of finite length for both frequency and time domain

Summary The subsurface electric fields of a current-carrying cable are examined for both steady-state and transient situations. Closed form expressions are obtained for two of the electric field components, and a numerical integration is used to obtain the third component. Waveforms for a stepfunction current excitation are displayed. The results have possible application to pulsed downlink communication in mine rescue operations.     

Ferromanganoan sediments in the equatorial East Pacific

Ferromanganoan sediments containing little or no CaCO₃ have been found to occur extensively throughout the region between the East Pacific Rise and the Galapagos Rise. Concentrations of Fe and Mn of up to 18 and 6.5%, respectively, accompany low concentrations of Al and Ti. The concentrations of Cu, Ni, and Zn are also high relative to more typical pelagic sediments.While chemically similar to the non-carbonate fraction of metalliferous sediments previously described from the East Pacific Rise, the mineralogy is markedly different. A non-detrital smectite makes up the bulk of sediment (70 to 90%) and is the most important iron bearing phase. Fe and Mn oxides, occurring primarily as micro-nodules, comprise 10 to 20% of the sediment. Detrital material is relatively rare, amounting to less than 10% in all samples.     

Carbon monoxide on the primitive earth

The reaction of CO + OH^? in aqueous solution to give formate was studied as a carbon monoxide sink on the primitive earth and in the present ocean. The reaction is first order in OH^? and first order in the molar CO concentration. The second order rate constant is given by log k(M^?1hr^?1) = 15.83?4886/T between 25°C and 60°C. Using the solubility of CO in sea water, and assuming a pH of 8 for a primitive ocean of the present size, the halflife of CO in the atmosphere is calculated to be 12 × 10⁶ yr at 0°C and 5.5 × 10⁴ yr at 25°C.Three other CO sinks would have been important in the primitive atmosphere: CO + H₂ → H₂CO driven by various energy sources, CO + OH → CO₂ + H, and the Fischer-Tropsch reaction of CO + H₂ → hydrocarbons, etc. It is concluded that the lifetime of a CO atmosphere would have been very short on the geological time scale although the relative importance of these four CO sinks is difficult to estimate.The CO + OH^? reaction to give formate is a very minor CO sink on the earth at the present time.     

Effect of thermal effluent on migrating menhaden

Hot water effluent from power stations kills juvenile menhaden migrating through Long Island Sound. Since the fish sink to the bottom, losses are unrecorded or at best under-estimated. Other fish are probably also affected. Menhaden in Long Island Sound contribute to the commercial fishery off the eastern seaboard of the United States. At present the losses have little impact on the fishery, but if the projected increase in hot water discharges into the Sound materializes the consequences may be serious.     

Adjusting to Policy Expectations in Climate Change Modeling

This paper surveys and interprets the attitudes of scientists to the use of flux adjustments in climate projections with coupled Atmosphere Ocean General Circulation Models. The survey is based largely on the responses of 19 climate modellers to several questions and a discussion document circulated in 1995. We interpret the responses in terms of the following factors: the implicit assumptions which scientists hold about how the environmental policy process deals with scientific uncertainty over human-related global warming; the different scientific styles that exist in climate research; and the influence of organisations, institutions, and policy upon research agendas. We find evidence that scientists' perceptions of the policy process do play a role in shaping their scientific practices. In particular, many of our respondents expressed a preference for keeping discussion of the issue of flux adjustments within the climate modeling community, apparently fearing that climate contrarians would exploit the issue in the public domain. While this may be true, we point to the risk that such an approach may backfire. We also identify assumptions and cultural commitments lying at a deeper level which play at least as important a role as perceptions of the policy process in shaping scientific practices. This leads us to identify two groups of scientists, pragmatists and purists, who have different implicit standards for model adequacy, and correspondingly are or are not willing to use flux adjustments.     

Monthly suspended sediment load prediction using artificial intelligence: testing of a new random subspace method

ABSTRACT

The predictive capability of a new artificial intelligence method, random subspace (RS), for the prediction of suspended sediment load in rivers was compared with commonly used methods: random forest (RF) and two support vector machine (SVM) models using a radial basis function kernel (SVM-RBF) and a normalized polynomial kernel (SVM-NPK). Using river discharge, rainfall and river stage data from the Haraz River, Iran, the results revealed: (a) the RS model provided a superior predictive accuracy (NSE = 0.83) to SVM-RBF (NSE = 0.80), SVM-NPK (NSE = 0.78) and RF (NSE = 0.68), corresponding to very good, good, satisfactory and unsatisfactory accuracies in load prediction; (b) the RBF kernel outperformed the NPK kernel; (c) the predictive capability was most sensitive to gamma and epsilon in SVM models, maximum depth of a tree and the number of features in RF models, classifier type, number of trees and subspace size in RS models; and (d) suspended sediment loads were most closely correlated with river discharge (PCC = 0.76). Overall, the results show that RS models have great potential in data poor watersheds, such as that studied here, to produce strong predictions of suspended load based on monthly records of river discharge, rainfall depth and river stage alone.