A synopsis of climatic and vegetational change in Southeast Asia

Tropical rain forest in Southeast Asia has developed within an extensive archipelago during the past 65 million years or more. During the Miocene (beginning 25 million years BP), rain forest extended much further north (to southern China and Japan); since that time it has contracted. During the Pleistocene (beginning 2.0 million years BP), development of continental glaciers at high latitudes was associated in Southeast Asia with lowered sea level, cooler temperatures, and modified rainfall patterns. Fossil pollen records demonstrate that Southeast Asian vegetation during the last glacial maximum (ca. 18 000 BP) differed substantially from that of today, with an increase in the extent of montane vegetation and savannah and a decline in rain forest. These data show that the distribution and extent of rain forest in Southeast Asia has historically been quite sensitive to climatic change.     

Arctic hazes in summer over Greenland and the North American Arctic: II. Nature and concentrations of accumulation-mode and giant particles

Airborne measurements made during August 1985 over Greenland and its environs show that both accumulation-mode (0.1 m D2.0 m) and giant (D2 m) particles were present in relatively high concentrations in arctic haze layers and that the accumulation-mode particles dominated light scattering. Particles with diameters (D) between 1 and 4 m consisted predominately of mixed materials, small and dense inclusions, and probably organic compounds containing sulfur. Many of the particles from 0.1 to 1 m in diameter were also of mixed composition, with sulfuric acid, ammonium sulfate and organics probably the dominant constituents.     

The use of general circulation models in the analysis of the ecosystem impacts of climatic change

The use of general circulation models in the estimation of the impact of climatic change on the global ecosystem is seen to depend primarily on their ability to reliably depict the seasonal and geographical distribution of the changes in surface climate variables. While present GCMs generally simulate the observed distribution of surface air temperature reasonably well, they show significantly different changes in the equilibrium temperature as a result of doubled CO₂, for example. These disagreements are attributed to differences in the model's resolution and parameterization of subgrid-scale processes. Such model-dependent errors notwithstanding, much more information of possible use in impact analysis can be extracted from general circulation model simulations than has generally been done so far. The completeness, consistency and experimental possibilities offered by simulated data sets permit the systematic extraction of a wide variety of statistics important to the surface ecosystem, such as the length of the growing season, the duration of rainless periods, and the surface moisture stress.Assuming further model improvements, the elements of a model-assisted methodology for climate impact analysis are seen to be: (1) the determination of the seasonal and geographical distribution of that portion of simulated climatic changes which are both statistically and physically significant; (2) the transformation of the (significant) large-scale climatic changes onto the local scale of impact (the climate inversion problem); and (3) the design of specific statistical parameters or functions relevant to local ecosystem impacts.     

The attenuation of chemical elements in acidic leachates from coal mineral wastes by soils

The chemical attenuation of acidity and selected elements (aluminum, arsenic, cadmium, cobalt, chromium, copper, fluorine, iron, manganese, nickel, and zinc) in acidic leachates from coal mineral wastes by four natural subsurface soils has been investigated using laboratory column methods Leachate solutions were allowed to percolate through the soils under simulated natural flow conditions, and the elemental concentrations in the influents and effluents were measured periodically Elemental retentions were substantial for all species except managanese, which was eluted in excess from all soils except the most calcareous Two processes appeared to operate in decreasing influent concentrations: (1) precipitation of solid phases caused by increased pH of the leachate as it percolated through the soil, and (2) adsorption of elements onto exchange and sorption sites naturally present in the soil and on iron and aluminum oxide precipitates formed in situ from leachate components because of the increased pH The soil property most important in retention was its alkalinity Thus, carbonaceous soils provide the best control material for acidic leachates from coal mineral wastes. Results show that natural soils can substantially reduce pollutant fluxes to the environment from acidic coal waste dumps and should be considered when selecting waste disposal sites Performed under the auspices of the U.S. Department of Energy     

Micro Computers Applied to Ground Water Monitoring and Testing

Micro computers have been demonstrated to be a most valuable, cost-effective means of long- and short-term data acquisition for ground water investigations and installations. A system can readily be assembled for the cost of labor saved in the field, or for the same cost as other conventional instruments, which perform only a fraction of the functions of the computer system
Documented in this article are systems which have been developed and used for simultaneous monitoring of several wells during aquifer tests, and systems installed for long-term monitoring of piezometric surface fluctuations. Both systems can be contained in a small suitcase or insulated cooler. Specific features of the systems include multiple channel capacity, one-month maintenance period, variable computer controlled reading intervals, magnetic tape data storage, data reduction and analysis capabilities while maintaining monitoring, graphic display of time and measurements, hard copy capability and barometric pressure change corrections.
Other applications are examined for the complete control of pumping tests, including pumping rate; in situ permeability tests; monitoring changes; and even strain. The pressure transducer system may also be applied for river gauging and current measurement.     

Determination of evaporation from integrated profiles of humidity and temperature over an inhomogeneous surface

In this study a moderate-sized alfalfa field was downwind of a large dry region. Measured vertical profiles of temperature, humidity and wind at upwind and downwind sides of the field were used to calculate the short-term evaporation rate, as well as the contribution of horizontally transported or advected heat energy to the evaporation. The vertical profiles must be measured at least to the height at which air is modified by the new surface. In this case that height was as large as 18 m over a several hundred meter long traverse.Evaporation rates calculated by such an approach were in very close agreement to surface fluxes measured by an eddy correlation system near the surface. The difference between calculated and measured values averaged 9.5%. The reduction in sensible heat content of the air of the control volume was substantial during passage over the field. If all this energy was assumed to have been used in evaporation, then the advection of heat contributed from 35 to 86% of the total evaporation rate.It appears that for an inhomogeneous surface, knowledge of the distortion of some properties of local boundary layers can yield reliable estimates of local evaporation. The approach has little empiricism as it is based on simple conservation laws.     

Bank conditions and erosion along selected reservoirs

This analysis was done as the preliminary step in an ongoing study of reservoir bank erosion processes that are active in the northern U.S. The objectives of this analysis were to observe and document bank characteristics, conditions, and changes along reservoirs with eroding banks, to estimate the amounts of historical bank recession and to discuss its possible causes. Aerial photographs were used to observe the historical bank changes and estimate bank recession. Site reconnaissance, discussions with on-site personnel, and published reports were used to evaluate possible relationships between the local erosion and bank conditions. As part of this analysis linear regressions were done to determine if the estimated recession rates correlate with selected bank and climatic conditions and with physical characteristics of the reservoirs. The regression results, however, were generally not useful because they suggested relationships that are contrary to field observations and published results. Dominant bank erosion processes were wind-wave erosion, capillary wave erosion during high-water periods, groundwater-induced sliding, freeze-thaw processes, rain splash and rainwash, and boat waves. However, because of the complexity of the interrelationships of these and many other bank erosion processes and the variability of the processes at and between sites, it would be necessary to make site-specific measurements and observations year-round to evaluate the processes that are active along a particular bank.