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The application of Raman spectroscopy to the determination of the aromatic content of gasolines and aviation fuels is reported. Since aromatic components have very high Raman cross-sections owing to large polarizability changes under laser excitation, bands from these components will dominate specific Raman spectral regions. It is expected, therefore, that Raman scattering will be a particularly useful approach to broadly characterizing the fuel hydrocarbon makeup for aromatic content and the properties of fuels which are influenced by aromatic content.

A general circulation model is modified successively by adding five new features in the lower boundary layer; namely, (i) a different roughness parameter over land and sea, (ii) a Monin-Obukhov type treatment of the turbulent transfer process in the constant-flux layer, (iii) a Richardson number dependent parameterization for Ekman layer process, (iv) a diurnal variation of insolation, and (v) heat conduction into the soil. To assess the effect of each, the experiments are repeated by gradually increasing the complexity of the model. The circulation model has relatively low horizontal grid resolution and 9 vertical levels, and it is applied to a winter case for 14 day predictions. The results indicate that the sophistication of the boundary layer physics does not produce a particularly large effect on the synoptic scale prediction until about 7 days. Its effect may become large after 10 days. One noteworthy result is that the effect of the diurnal variation of insolation is not great for the free atmosphere but an influence is effectively transferred in the vertical, if the Richardson number dependent parameterization for the Ekman layer process is incorporated. The entire study is a preliminary test, the purpose of which is to determine the relative magnitude of each effect. A detailed comparison with observed data was not attempted.

The generation of widespread pressure oscillations in southern Australia on 26–27 January 1960 is examined in some detail, by means of available barograms, and spectral analysis of a Melbourne Dines microbarogram. Photographs of mamma cloud taken at Adelaide give some insight into the processes at work producing both cloud form and oscillations. It is concluded that the oscillations were due to wave motions on an interface with large density contrast, at about 1,500 m altitude, and that these motions propagated approximately in the direction of vertical shear, with the velocity of the wind at about 2·5 km. Their phase and group velocities were similar, and their wavelengths in the range 10–70 km. These waves appear to have been transmitted over great distances without marked attenuation. An estimate of the energy of oscillation was compared with that which could be imparted to a horizontal interface with strong shear by the passage of downdraughts through it, and the conclusion is reached that the combination of downdraughts and shear could have provided the energy. On the other hand, there is good evidence that the waves were unstable, and could therefore have drawn their energy from that of the mean motion. Examination of other occasions on which marked pressure oscillations occurred suggested that fallout and strong shear were both necessary conditions.

Winds and temperatures in the boundary layer measured during two Australian expeditions are analysed according to the similarity scheme, with the use of four stability classifications. Under conditions of deep convection there is a minimum potential temperature and a maximum velocity component in the direction of the surface wind, at a height of about 0.12 u*/f. In the very stable cases, the temperature gradient follows rather closely a z−2 law for a considerable height range from 0.08 u*/f upwards. An expression closely fitting the mean data in stable conditions is suggested for the vertical temperature structure at all levels in the boundary layer. Wind data processed in this way show, for all four stability classes, a rudimentary Ekman spiral. With deep convection the spiral is found to be reversed in sense, but the flow in the convecting layer is down the gradient of pressure. If the convective limit lies broadly within the Ekman layer, a spiral of the expected sense is found. The upper limit of the Ekman layer (as defined by the ‘spiral’) is found to lie at a height of 0.17 to 0.24 (increasing with stability) in units of u*/f. Stress and heat-flux are apparently considerable above this level, with sub-geostrophic wind, when deep convection is occurring. Approximations to the universal distributions of stress, eddy coefficients, mixing length and rate of degradation of mean flow kinetic energy are computed for the various stabilities. The mixing length in unstable conditions increases almost as height up to a level of about 0.08 u*/f, and then decreases, but in general appears not to vanish in stable layers above the boundary layer. In the unstable boundary layer with deep convection, the eddy transfer coefficient for heat exceeds that for momentum up to 0.12 u*/f, where it becomes infinite, and is negative at higher levels. In stable conditions the transfer coefficients for a small sample of soundings were estimated to be closely similar. The universal functions of stability, A, B and C, which enable one to compute free atmosphere wind vector and temperature, given surface conditions, have been evaluated with moderate success, although B, which essentially describes the change of wind direction with height, exhibits excessive variability. A method is suggested for computing horizontal advection in the boundary layer when this is to be ‘parameterized’ in mathematical models. The drag coefficient, in terms of free atmosphere wind, has almost a 50-fold range, due to stability variation only. Most of the variation occurs relatively close to neutral, so warning against too ready an assumption of neutrality in practical applications. It is suggested that, for modelling purposes, it is preferable to adopt boundary layer formulations which are not too sensitive to departures from ideal conditions, and eddy coefficients, perhaps based on mixing lengths, may well provide the best approach currently available.

Boundary layer data from the Wangara expedition show that, at a point in the mean winter west wind belt (but near its equatorward limit), eddies on the synoptic scale (periods greater than a day) transferred westerly momentum upward. Except in the lowest 500 m, this upward tranfer predominated over downward fluxes due to micro-scale (periods less than 2 hours) and meso-scale (2 - 24 hours) eddies, the latter transfers being very small. The effect of ageostrophic motions, due to accelerations, on this transfer was negligibly small. A characteristic circulation, relative to synoptic systems, in a vertical zonal plane, performing the vertical transfer of westerly momentum, has been deduced. The eddy flux of angular momentum, in the middle latitude boundary layer between 500 and 1,700 m appears to be directed up the angular momentum gradient, both horizontally and vertically, and, at all levels, down the horizontal gradient of angular velocity. An argument is presented to show that the intensity of circulation in the Ferrel cell may be greater than is usually estimated, the maximum absolute value of the stream function (except for the Northern Hemisphere in summer), being normally at least about 30 × 1012 g s−1.

Temporal spectra and cross-spectra of the three turbulent wind components for meso-synoptic scales at 250 m vertical intervals in the planetary boundary layer are presented. The data were derived from hourly simultaneous balloon ascents from a 5-point grid at Hay, New South Wales, Australia (lat. 34 ½S), during the Wangara expedition. The spectra indicate a meso-scale gap for u (eastward component of wind) and v (northward component). The computed w-spectra suggest that no marked gap is present. For periods less than 1 day the u- and v-spectra, with a correction applied for high frequency noise, fall off approximately as n−2·6, where n is the frequency, and this result appears to be invariant with height within and just above the planetary boundary layer. The corrected w-spectra exhibit n−1 dependency in this frequency range. The uv, uw, and vw cospectra also show only small contributions on the meso-scale (periods less than a day) compared to the synoptic scale, indicating that meso-scale motions may not have to be explicitly modelled in atmospheric general circulation models. An inertial peak is found for u and v but the w-spectra show a diurnal peak. The phase angles showed that u and v were in approximate quadrature at the inertial frequency, demonstrating the existence of the inertial cycle. Tests for horizontally two-dimensional isotropy indicated that the turbulence did not obey this simplification.