933 resultados para Spatial and Temporal Pattern
Calcium carbonate and organic carbon content, and stable isotope composition of sediment core V19-27
Resumo:
It is commonly understood that the observed decline in precipitation in South-West Australia during the 20th century is caused by anthropogenic factors. Candidates therefore are changes to large-scale atmospheric circulations due to global warming, extensive deforestation and anthropogenic aerosol emissions - all of which are effective on different spatial and temporal scales. This contribution focusses on the role of rapidly rising aerosol emissions from anthropogenic sources in South-West Australia around 1970. An analysis of historical longterm rainfall data of the Bureau of Meteorology shows that South-West Australia as a whole experienced a gradual decline in precipitation over the 20th century. However, on smaller scales and for the particular example of the Perth catchment area, a sudden drop in precipitation around 1970 is apparent. Modelling experiments at a convection-resolving resolution of 3.3km using the Weather and Research Forecasting (WRF) model version 3.6.1 with the aerosol-aware Thompson-Eidhammer microphysics scheme are conducted for the period 1970-1974. A comparison of four runs with different prescribed aerosol emissions and without aerosol effects demonstrates that tripling the pre-1960s atmospheric CCN and IN concentrations can suppress precipitation by 2-9%, depending on the area and the season. This suggests that a combination of all three processes is required to account for the gradual decline in rainfall seen for greater South-West Australia and for the sudden drop observed in areas along the West Coast in the 1970s: changing atmospheric circulations, deforestation and anthropogenic aerosol emissions.
Calcium carbonate and organic carbon content, and stable isotope composition of sediment core V19-28
Resumo:
We present for the first time all 12 d18O records obtained from ice cores drilled in the framework of the North Greenland Traverse (NGT) between 1993 and 1995 in northern Greenland. The cores cover an area of 680 km × 317 km, 10 % of the Greenland ice sheet. Depending on core length (100-175 m) and accumulation rate (90-200 kg/m**2/a) the single records reflect an isotope-temperature history over the last 500-1100 years. Lowest d18O mean values occur north of the summit and east of the main divide as a consequence of Greenland's topography. In general, ice cores drilled on the main ice divide show different results than those drilled east of the main ice divide that might be influenced by secondary regional moisture sources. A stack of all NGT records and the NGRIP record is presented with improved signal-to-noise ratio. Compared to single records, this stack represents the mean d18O signal for northern Greenland that is interpreted as proxy for temperature. Our northern Greenland d18O stack indicates distinctly enriched d18O values during medieval times, about AD 1420 ± 20 and from AD 1870 onwards. The period between AD 1420 and AD 1850 has depleted d18O values compared to the average for the entire millennium and represents the Little Ice Age. The d18O values of the 20th century are comparable to the medieval period but are lower than that about AD 1420.
Resumo:
The city of Malaga underwent considerable growth in the 19th and 20th centuries. The territorial expansion paired with a massive influx of immigrants occurred in three waves and as a consequence the city of Malaga remains divided into three different parts up to today. The differences between these three neighbourhoods of the city lie in the type of houses, different cultural and industrial activities, socioeconomic level, and very interestingly, also in speech. Thus, the aim of this study is an examination of the interrelation between speech (phonetic features) and urban space in Malaga. A combination of quantitative and qualitative analysis was used, based on two types of data: 1) production data stemming from recordings of 120 speakers; 2) perception data (salience, estimated frequency of use, attitude, spatial and social perception, imitation) which was collected from several surveys with 120 participants each. Results show that the speech production data divides the city of Malaga clearly into three different parts. This tripartition is confirmed by the analysis of the perception data. Moreover, the habitants of these three areas are perceived as different social types, to whom a range of social features is attributed. That is, certain linguistic features, the different neighbourhoods of the city and the social characteristics associated with them are undergoing a process of indexicalization and iconization. As a result, the linguistic features in question function as identity markers on the intraurban level.
Resumo:
In a traditional system of exogamous and patrilocal marriage prevalent in much of Sub-Saharan Africa, when she marries, a rural woman typically leaves her kin to reside with her husband living outside her natal village. Since a village that allows a widow to inherit her late husband's land can provide her with old age security, single females living outside the village are more likely to marry into the village. Using a natural experimental setting, provided by the longitudinal household panel data drawn from rural Tanzania for the period from 1991 to 2004, during which several villages that initially banned a widow's land inheritance removed this discrimination, this study provides evidence in support of this view, whereby altering a customary land inheritance rules in a village in favor of widows increased the probability of males marrying in that village. This finding suggests that providing rural women with old age protection (e.g., insurance, livelihood protection) has remarkable spatial and temporal welfare effects by influencing their decision to marry.