Particulate dispersion from sources within a forest

Particulate dispersion from sources within a 10- to 13-m tall pine forest was studied experimentally at Brookhaven National Laboratory using stained ragweed pollen and other tracers ranging from 14 to 58 m in size. Forty-seven continuous point source releases lasting from 22 to 55 min were made at heights from 1.75 to 14.0 m from locations having a long fetch through the forest. In most experiments, differently colored ragweed pollen were emitted simultaneously from three locations. In other tests, several particle types were released from a single point. The sampling network consisted of 119 rotoslide samplers at heights from 0.5 to 21.0 m at 57 positions within and at the edge of the forest. Deposition to the ground was sampled by greased microscope slides at each position. Meteorological measurements were taken in and near the forest.Data were classified by particle characteristics, source height and meteorological parameters. Concentration patterns were illustrated on scale diagrams of the sampling grid. Changes in centerline and crosswind integrated concentrations, plume width and height, mass flux, deposition and deposition velocity were studied as a function of distance, particle size and wind speed. Results were compared to those obtained from similar releases over open terrain.In the forest, vertical predominates over lateral dispersion and considerable interchange occurs through the canopy. Flow is channelled somewhat by vegetation density differences but is generally in the direction of the mean wind above the forest. No systematic turning of the wind with height was observed. Most particles are lost to the foliage rather than to the ground and large particles are lost more rapidly than smaller ones. Rate of change in mass flux is similar to that over open terrain and is greater with light than with stronger wind speeds.This research was carried out under the auspices of the New York State Museum and Science Service and the U.S. Atomic Energy Commission (now Energy Research and Development Administration) and was partially supported by Research Grant No. R-800677 from the Division of Meteorology, U.S. Environmental Protection Agency.     

Formation and characteristics of coastal internal boundary layers during onshore flows

The development and characteristics of coastal internal boundary layers were investigated in 28 tests. These were made at all seasons and in both gradient and sea-breeze flows but only during mid-day periods. Measurements of turbulence and temperature were taken from a light aircraft which flew traverses across Long Island at successive altitudes parallel to the wind direction. These were used to locate the boundary between modified and unmodified air as a function of height and distance from the coast. The same measurements plus tower measurements of wind, turbulence and temperature, pilot balloon soundings and measurements of land and water surface temperatures by a remote sensing IR thermometer were used to quantify the characteristics of the modified and unmodified air. The boundary layer slope was steep close to the land-water interface and became shallower with downwind distance. Growth of the boundary layer was initially slower with stable lapse rates upwind than with neutral or unstable conditions over the water. An equilibrium height was found in many tests except under conditions of free convection when the internal boundary layer merged into the mixed layer inland and with sea-breeze conditions. The equilibrium height depended on downwind conditions and was greater with low wind speeds and strong land surface heating than with stronger winds and small land-water temperature differences. Current theoretical models are not adequate to predict the height of the boundary layer at the altitudes and distances studied but reasonably good predictions were given by an empirical model developed earlier. Wind speed in the modified air averaged about 70% of that at the coast but turbulence levels were several times higher both near the surface and aloft. These findings have important implications for diffusion from coastal sites.     

Calibration and use of a sailplane variometer to measure vertical velocity fluctuations

The calibration of a sailplane variometer to measure vertical velocity fluctuations in the atmospheric boundary layer is described. Its usefulness is demonstrated with typical results from a boundary-layer development study. The atmospheric calibrations gave the ratio of standard deviations of vertical velocity fluctuations measured by a standard tower-mounted turbulence instrument to the values measured by variometer as 2.5 m s^–1 V^–1.     

Spinel to garnet lherzolite transition in relation to high temperature palaeogeotherms,eastern Australia∗

Eastern Australian xenolith suites and lithospheric transition zones are re‐evaluated using new mineral analyses and thermo‐barometry. Some suites, including that defining the southeastern Australian geotherm, are not fully equilibrated. New pressure‐temperature estimates, based on experimental calibrations that allow for Cr and Ti in pyroxenes, differ from earlier results by up to 0.6 GPa and 250°C. The preferred Brey and Köhler 1990 thermo‐barometer indicates a shallower cooler garnet lherzolite transition under Mesozoic New South Wales (50 km depth at 980° C) than for Tertiary Tasmania (60 km depth at 1090°C).

Deviations between palaeogeotherms may reflect: (i) higher temperature gradients for Tasmania and New South Wales (by 100°C/0.1 GPa) related to abnormally hot mantle; (ii) higher temperature gradients linked to more voluminous magmatism, largely Cenozoic in age; and (iii) complex temperature perturbations linked to different levels of magmatic intrusion.

These deviations blur reconstructions of lithospheric assemblages, where temperature is determinable and pressure comes from an assumed geotherm. Potential errors in locating spinel lherzolite and crust‐mantle transition assemblages may reach 15 km in depth. The highest Tertiary geothermal gradients in Tasmania and northeastern New South Wales match those from regions of active lithospheric extension. The young southeastern Australian geotherm is decaying from a higher temperature equilibration, based on experimental work, and Mesozoic New South Wales geotherms trend towards the lower gradients of bounding cratons.     

Early applications of computer technology to dynamical astronomy

The review traces the progress from the early application of the Hollerith Tabulating Machine to the construction of astronomical tables by interpolation and to the evaluation of Brown's Tables of the Moon by L. J. Comrie in the late 1920's and early 1930's to the introduction of large programmable electronic calculators in the post World War II era. The early application of electromechanical punched-card machines to astronomical problems stemmed from the needs of the national ephemeris offices to evaluate theories of the Sun, Moon and planets and to subtabulate these positions to form the tables of daily values given in the national almanacs. These techniques were quickly applied to other astronomical problems such as the construction of star catalogs, the reduction of astrometric observations and the numerical integration of the equations of motion of objects in the solar system.     

Reliability of experimental partition coefficients in carbonate systems: Evidence for inhomogeneous distribution of impurity cations

Electron spin resonance (ESR) spectroscopy, thermal analysis and X-ray diffraction (XRD) analysis are used to study the mode of incorporation of a wide range of impurity ions (up to 1% Ni²⁺, Sr²⁺, Cd²⁺, Mg²⁺, Cu²⁺, Fe²⁺, Zn²⁺, Pb²⁺, Mn²⁺ and Ba²⁺) in calcites synthesised in aqueous solutions. It is shown that when certain impurity ions are incorporated in these calcites they become concentrated, together with other trace elements such as Mn²⁺, into hitherto unsuspected trace phases. The important conclusion is drawn that unless the scavenging of trace elements by these phases can be avoided or corrected for, any calcite—liquid partition coefficients measured may have limited significance. ESR spectroscopy has revealed the intense strain common in calcites grown by different methods, whilst thermal analysis suggested that such strain may significantly alter the thermodynamic properties of these calcites. ESR spectroscopic analysis of aragonites synthesised by methods previously reported in the literature has revealed the common occurrence of trace calcite at concentrations below the XRD detection limit and proves the tendency of this calcite to scavenge trace Mn. Using ESR spectroscopy to monitor trace calcite levels and structural imperfections in synthetic aragonites, the urea hydrolysis technique is modified to provide a method for the synthesis of high-purity strain-free aragonite available for experimental studies.     

Calibration and Use of a Sailplane V Ariometer to Measure Vertical Velocity Fluctuations

The calibration of a sailplane variometer to measure vertical velocity fluctuations in the atmospheric boundary layer is described. Its usefulness is demonstrated with typical results from a boundary-layer development study. The atmospheric calibrations gave the ratio of standard deviations of vertical velocity fluctuations measured by a standard tower-mounted turbulence instrument to the values measured by varioumeter as 2.5 m s⁻¹ V⁻¹.     

Particulate dispersion into and within a forest

Particulate dispersion into and within a 10- to 13-m tall pine forest was studied experimentally at Brookhaven National Laboratory using stained ragweed pollen and other tracers ranging from 14 to 54 m in diam. Seventy-two continuous point source releases lasting 20 to 40 min were made at various distances from within the forest edge to 60 m upwind and at heights of 1.75 to 14.0 m. In most experiments, differently colored ragweed pollen was released simultaneously from three locations. Thirty-six longer tests were made using pollen from area sources of ragweed and three with pollen from distant sources. All tests were made during the day with steady winds and unstable lapse rates outside the forest. The sampling network consisted of 119 rotoslide samplers mounted at heights from 0.5 to 21.0 m at 57 positions extending 100 m into the forest. Deposition was sampled by greased microscope slides at each sampling position. Meteorological measurements were taken in and near the forest.Data were classified by particle characteristics; by source type, distance and height; and by meteorological parameters. Isopleths were drawn on scale diagrams of the sampling grid to illustrate concentration patterns. Changes in centerline concentration, crosswind integrated concentration, mass flux, plume width, plume height, deposition, and deposition velocity were related to distance within the forest and other variables. Results were compared to those of similar releases over open terrain and those of previous forest dispersion studies elsewhere.The plume approaching the forest is broadened both vertically and horizontally by increased turbulence at the forest edge and flows mainly into the trunk space and above the forest. Lateral spread is slow within the forest, but vertical spreading beyond the entrance region is greater than in the open. Particles become mixed uniformly below the canopy while appreciable interchange takes place through this layer. Concentration within the forest decreases at a faster rate than in the open, but change in total mass flux within and above the forest is not significantly different. Loss of material takes place by impaction near the forest edge and in the tree tops and by deposition within the forest. Most loss takes place to the foliage rather than the ground, and larger particles are lost faster than smaller ones.This research was carried out under the auspices of the New York State Museum and Science Service and the U.S. Atomic Energy Commission and was partially supported by Research Grant No. R-800677 from the Division of Meteorology, U.S. Environmental Protection Agency.