An intercomparison of seawater filtration procedures

Filtration systems, used for the preparation of coastal seawater samples for trace analysis, have been intercompared to determine the extent of contamination arising during the filtration process. The results show that all the systems intercompared are able to provide uncontaminated filtrates for copper, nickel, cobalt and manganese and, with two exceptions, for cadmium and iron, at levels that would be encountered in uncontaminated coastal waters.     

Trace gas measurements during aircraft flights in the tropopause region over Europe and North Africa

During aircraft flights in May 1981 from Munich (40°N) to north of the Spitsbergen Islands (82°N) and to Monrovia, Liberia (6°N), air samples were obtained in the altitude range of 8 to 11 km and during the ascents and descents near the airports. These samples have been analyzed for the trace gas mixing ratios of CH₄, CO and N₂O. The results of these analyses are presented and discussed.The results provide new evidence of tropospheric-stratospheric exchange events in the vicinity of the subpolar and subtropical tropopause foldings and possibly show a case of transport of CO-enriched air in the upper troposphere above the North Atlantic Ocean.     

The southern agglomeration zone of the GDR — Regional structure and development

Agglomeration areas in the GDR are those regions, which are characterized by an above average level of regional concentration of productive forces and their conditions of reproduction. The economic potential concentrated in these regions represents a large part of the national economy. It is possible to describe the territorial structure of these agglomeration areas by general indices (agglomeration core — agglomeration field — agglometation fringe; polycentric node-band-structure), but also the individual features of each one of these regions are to be attended. They are expressed for the first time by several forms of localization of plants and by the structure of settlements and settlement networks. The present main tendencies in the development of the agglomeration regions are:

They succeeded in minimizing the regional disparities of productivity between different agglomeration regions and within them, and in stabilizing the economic position of these regions by systematic measures for investment and rationalization and the hereby influenced structural changes.

At present and up to 1990 the completion of housing programme is of foremost importance by which the main activities will shift from the urban fringe to the centres of the cities; provincial towns and smaller settlements will also participate in this programme.

The main target of these activities is to remove imperfect structures and other burning problems of the agglomeration regions step by step. Geographical Institutes are dealing with the management of these tasks too.     

Possible influences of solar radiation variations on the atmospheric circulation in the northern hemisphere of the earth

The strength of the circumpolar zonal circulation of the atmosphere in the northern hemisphere, expressed by an index calculated from the air pressure gradient between 35° N and 65°N, shows a remarkable secular change in this century in the years 1935 to 1938, and probably again in the years after 1970. A contemporary change and parallel course with a high positive correlation can be found in a solar radiation index calculated by means of sunspot numbers and solar faculae areas. A good correlation was also found between this solar radiation index and a series of UV measurements on Mt. Wilson. The possible mechanism of action in the atmosphere will be discussed, and it is shown that this solar radiation index is also correlated with circulation parameters in the troposphere and stratosphere over Europe. There are indications of a decrease of the action from the upper to the lower atmosphere. The consequences of this secular change of circulation for the climatic history in the 20th century in Europe are presented and from that a hypothetical retrospective view of the European climatic history before the 20th century, based on the total series of sunspot numbers, is briefly discussed. In a general view with smoothed data it can be concluded that the sun seems to determine the basic structure of the north hemispheric circulation in middle latitudes, if a strong influence of sunspots and solar faculae on the solar radiation is assumed.     

Transport rate of drifting snow and the mean wind speed profile

Transport rates, measured by weighing snow blown into a filter fabric trap, were greater over hard snow or ice than for the same wind speed over soft, fresh snow surfaces. Analysis of wind speed profiles from nine blizzards showed that friction between moving particles and the surface was less, and particle speeds were greater over hard surfaces. Transport rates at a given wind speed increased rapidly as aerodynamic roughness decreased in the rough-smooth transition region. Bagnold's theory for bed load transport provided a useful framework for the analysis.     

Cyclotella-taxa (Bacillariophyceae) in lakes of the Alpine region and their relationship to environmental variables

Surface sediment diatom assemblages for 86 Alpine lakes were analysed focusing on the dominant genusCyclotella and corresponding environmental data. The range of morphological variability of theCyclotella bodanica/radiosa, C. distinguenda, C. ocellata, C. comensis andC. stelligera complexes was documented. Significance tests included in the canonical correspondence analysis (CCA) indicated that total phosphorus, conductivity and surface water temperature were significantly correlated withCyclotella taxa assemblage distribution. Numerical species optima and tolerances were calculated in respect to these significant variables using weighted averaging (WA) regression and calibration. CCA and WA were able to provide information about the environmental preferences of the various morphotypes observed.     

Vertical profiles of wind speed,snow concentration,and humidity in blowing snow

To estimate the sublimation rate of snow during relocation by wind, sizes and concentration of ice crystal fragments were measured at 6 levels in the lowest 1 m, during ten 10-min runs, in a nocturnal blizzard. Power-law functions of height described the decrease in mean particle diameter and concentration. The vertical gradient of water vapor, measured with a thermocouple psychrometer, was approximately linear from 0.2 to 1.0m above the surface. Evaporation of blowing snow over 3 km of transport distance was estimated to be 39% of transport rate, under conditions of the experiment.     

On the relationship of thunderstorm ice hydrometeor characteristics and total lightning measurements

Satellite-borne and ground-based devices for the detection of lightning offer the opportunity to explore relationships–on all significant scales up to global–between lightning frequency, f, and other thundercloud parameters. Calculations predict that f is proportional to the product of the downflux p of solid precipitation and the upward mass flux, I, of ice crystals. This prediction has received support from limited computational studies. The physical reasons for such a relationship are explained in terms of the paramount role of ice in the electrification of thunderstorms. Herein, this prediction is subjected to further, preliminary examination through analysis of lightning and dual-polarimetric radar data collected during the STERAO experiment conducted in Northern Colorado during the summer of 1996. The analysis has yielded some highly provisional support for this flux hypothesis. Computed trends of radar derived hydrometeor fractions of solid precipitation and small ice show correlation to the total lightning frequency and raise the possibility of determining values of p and/or I from lightning measurements.It is shown that the extent to which the observed correlations between f and both solid precipitation and small ice trends are or are not strong can provide an indication as to whether the lightning activity is limited by the available concentrations of precipitating or non-precipitating ice in the upper regions of the charging zone of the thundercloud, where most of the charge transfer occurs. It is demonstrated that the most accurate determinations of precipitation rate p from measurements of lighting frequency f are likely to be for conditions where the field-growth is limited by the availability of graupel pellets. It is shown that the simultaneous time variations of f and solid precipitation trends of the type obtained in the STERAO experiment could enable us to determine the nature of the dominant glaciation process operative in the thunderclouds studied.