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51.
Rodrigo J. Bombardi Leila M. V. Carvalho Charles Jones 《Theoretical and Applied Climatology》2014,118(1-2):251-269
The South Atlantic Convergence Zone (SACZ) is an intrinsic characteristic of the South American Summer Monsoon. In a recent study, we verified that the main mode of coupled variability over the South Atlantic (South Atlantic Dipole (SAD)) plays a role in modulating the position of extratropical cyclones that affect the SACZ precipitation. In this study, we perform numerical experiments to further investigate the mechanisms between SAD and the SACZ. Numerical experiments forced with prescribed SST anomalies showed that, even though the Atlantic SST affects the position of the cyclone associated with the SACZ, the atmospheric response and precipitation patterns over land are opposed to the observations. On the other hand, experiments forced with prescribed anomalous driving fields showed that the atmospheric component of SAD plays a significant role for the right position and intensity of precipitation associated with the SACZ. SAD negative anomalies provide the low-level and upper-level atmospheric support for the intensification of the cyclone at surface and for the increase in precipitation over the land portion of the SACZ. Therefore, the numerical experiments suggest that, during El Niño Southern Oscillation neutral conditions, the SACZ precipitation variability associated with SAD is largely dependent on the atmospheric variability rather than the underlying SST. 相似文献
52.
Rodrigo J. Bombardi Leila M. V. Carvalho Charles Jones Michelle S. Reboita 《Climate Dynamics》2014,42(5-6):1553-1568
The dominant mode of coupled variability over the South Atlantic Ocean is known as “South Atlantic Dipole” (SAD) and is characterized by a dipole in sea surface temperature (SST) anomalies with centers over the tropical and the extratropical South Atlantic. Previous studies have shown that variations in SST related to SAD modulate large-scale patterns of precipitation over the Atlantic Ocean. Here we show that variations in the South Atlantic SST are associated with changes in daily precipitation over eastern South America. Rain gauge precipitation, satellite derived sea surface temperature and reanalysis data are used to investigate the variability of the subtropical and tropical South Atlantic and impacts on precipitation. SAD phases are assessed by performing Singular value decomposition analysis of sea level pressure and SST anomalies. We show that during neutral El Niño Southern Oscillation events, SAD plays an important role in modulating cyclogenesis and the characteristics of the South Atlantic Convergence Zone. Positive SST anomalies over the extratropical South Atlantic (SAD negative phase) are related to increased cyclogenesis near southeast Brazil as well as the migration of extratropical cyclones further north. As a consequence, these systems organize convection and increase precipitation over eastern South America. 相似文献
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54.
Pathways for Participatory Water Governance in Ashaiman,Ghana: Learning from Institutional Bricolage and Hydrosocial Perspectives 总被引：1，自引：0，他引：1
Coupling a hydrosocial perspective with institutional bricolage, this research considers possibilities for participatory water governance in Ashaiman, a peri-urban settlement of Accra, Ghana. We explore three questions: (1) How do people in Ashaiman evoke ideas or experiences of water in general and water governance in particular? (2) What possibilities currently exist for engaging the community in key water-related decisions? (3) What possibilities exist for enhanced participatory water governance in this context, including potential for and interest in new institutions and engagement processes? Results of qualitative interviews and semistructured observation suggest that a siloed, water-centric approach inadequately captures everyday realities of water as hydrosocial and of existing institutions in Ashaiman. In contrast to “modern water,” we propose that water issues may be more meaningfully addressed as bundled with social welfare. Potential implications and alternative ways of understanding socio-institutional arrangements for participatory water governance are explored. 相似文献
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56.
Early Miocene benthic foraminifera and biostratigraphy of the Qom Formation, Deh Namak, Central Iran
A total of 165 samples were collected from the Qom Formation investigated in a stratigraphic section north of Deh Namak, in Central Iran. From these, 35 genera and 47 species of benthic foraminifera were identified. The age of the studied section is Early Miocene (Aquitanian to Early Burdigalian) based on the occurrence of Borelis melo curdica, Meandropsina anahensis, Meandropsina iranica, Elphidium sp. 14, Peneroplis farsensis, and Triloculina tricarinata. The thickness of the Qom Formation is 401 m of which 161.2 m is early Burdigalian in age. Foraminiferal assemblages in the Deh Namak section are referable to the Borelis melo group-Meandropsina iranica Assemblage Zone and Miogypsinoides-Archaias-Valvulinid Assemblage Zone of [Adams, T.D., Bourgeois, F., 1967. Asmari biostratigraphy. Iranian Oil Operating Companies, Geological and Exploration Division, Report1074 (unpublished) 1–37.] described originally from the Asmari Formation. 相似文献
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Ataollah Kavian Aazam Alipour Karim Soleimani Leila Gholami Pete Smith Jesús Rodrigo‐Comino 《水文研究》2019,33(2):261-270
The drastic growth of population in highly industrialized urban areas, as well as fossil fuel use, is increasing levels of airborne pollutants and enhancing acid rain. In rapidly developing countries such as Iran, the occurrence of acid rain has also increased. Acid rain is a driving factor of erosion due to the destructive effects on biota and aggregate stability; however, little is known about its impact on specific rates of erosion at the pedon scale. Thus, the present study aimed to investigate the effect of acid rain at pH levels of 5.25, 4.25, and 3.75 for rainfall intensities of 40, 60, and 80 mm h?1 on initial soil erosion processes under dry and saturated soil conditions using rainfall simulations. The results were compared using a two‐way ANOVA and Duncan tests and showed that initial soil erosion rates with acidic rain and non‐acidic rain under dry soil conditions were significantly different. The highest levels of soil particle loss due to splash effects in all rainfall intensities were observed with the most acidic rain (pH = 3.75), reaching maximum values of 16 g m?2 min?1. The lowest levels of particle losses were observed in the control plot where non‐acidic rain was used, with values ranging from 3.8 to 8.1 g m?2 min?1. Similarly, under saturated soil conditions, the lowest level of soil particle loss was observed in the control plot, and the highest peaks of soil loss were observed for the most acidic rains (pH = 3.75 and pH = 4.25), reaching maximum average values of 40 g m?2 min?1. However, for saturated soils with acidic water but with non‐acidic rain, the highest soil particle loss was observed for the control plot for all the rainfall intensities. In conclusion, acidic rain has a negative impact on soils, which can be more intense with a concomitant increase in rainfall intensity. Rapid solutions, therefore, need to be found to reduce the emission of pollutants into the air, otherwise, rainfall erosivity may drastically increase. 相似文献
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Groundwater contamination is a well-known phenomenon, which occurs on local and regional scales in Izeh polje. The aims of
this paper are investigation of the impact of human activities on the polje ecosystem, determination of the vulnerability
of ground water, and to solve environmental problems. Nitrate contamination of groundwater in the Izeh polje was predicted
using a solute transport model. The nitrate concentration in groundwater in most parts of Izeh polje is greater than maximum
concentration permissible for drinking water, i.e., 45 mg/l. The main source of nitrate in the eastern underground areas of
Izeh city is the domestic sewage. Bacterial pollution of shallow ground water in Izeh polje is severe and widespread. About
45% of ground water samples in May and September 2001 have positive MPN coliforms. Infiltration of polluted surface waters
and decrease of water table depth, have lead to bacterial pollution of 80% of ground water samples in January 2002. The northeast,
south and southwest areas of Izeh polje have higher pollution potential rather than its middle parts. The aquifer vulnerability
indices in the middle, eastern, and northern parts of the polje are moderately lower as a result of decreased sediment size
of the aquifer. The pollution in the polje depends on the amount and presence of pollutants. If they do exist, the possibility
of pollution is considerable due to the coarseness of materials and shallow depth of groundwater table. 相似文献
60.
Late-glacial (17–11 cal ka BP) pollen records from midwestern North America show similar vegetation trends; however, poor dating resolution, wide-interval pollen counts, and variable sedimentation rates have prevented the direct correlation with the North Atlantic Event Stratigraphy as represented in the Greenland ice-core records, thus preventing the understanding of the teleconnections and mechanisms of late-Quaternary events in the Northern Hemisphere. The widespread occurrence of late-glacial vegetation and climates with no modern analogs also hinders late-glacial climate reconstructions. A high-resolution pollen record with a well-controlled age model from Crystal Lake in northeastern Illinois reveals vegetation and climate conditions during the late-glacial and early Holocene intervals. Late-glacial Crystal Lake pollen assemblages, dominated by Picea mariana and Fraxinus nigra with lesser amounts of Abies and Larix, suggest relatively wet climate despite fluctuations between colder and warmer temperatures. Vegetation changes at Crystal Lake are coeval with millennial-scale trends in the NGRIP ice-core record, but major shifts in vegetation at Crystal Lake lag the NGRIP record by 300–400 yr. This lag may be due to the proximity of the Laurentide ice sheet, the ice sheet's inherent slowness in response to rapid climate changes, and its effect on frontal boundary conditions and lake-effect temperatures. 相似文献