| 1. |
- Berndtsson, Ronny
(författare)
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On the use of cross-correlation analysis in studies of patterns of rainfall variability
- 1987
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 93:1-2, s. 113-134
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Tidskriftsartikel (refereegranskat)abstract
- Cross-correlation structures based on daily rainfall data recorded during a period of 5 years at 67 stations throughout Tunisia are used to examine spatial rainfall variability. Basic properties of the correlation-distance function such as cumulating period, exclusion versus inclusion of dry periods, and data volume are analysed. Analysis of the correlation patterns for each month shows that two periods (February-May, and September-November) are delimited by a period of great instability (December-January) and by the dry period (June-August). Three main rainfall regions can be distinguished, delimited and governed mainly by the topography and the coastal influence.
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| 2. |
- Berndtsson, Ronny, et al.
(författare)
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Spatial and temporal characteristics of high-intensive rainfall in northern Tunisia
- 1986
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Ingår i: Journal of Hydrology. - 0022-1694. ; 87:3-4, s. 285-298
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Tidskriftsartikel (refereegranskat)abstract
- When dealing with urban design, it is essential to have knowledge of the magnitude of the spatial variability of short high-intensive rainstorms. Most of the studies of high-intensive rainfall, conducted during recent years, concern regions with a humid climate. Still, the largest temporal and spatial variations in rainfall are to be found in arid and semi-arid regions. This paper sums up findings regarding rainfall variability, observed in a small catchment in northern Tunisia during a period of 2 yr. Point and areal intensities are presented for the ten most high-intensive storms observed. Storm-centered areal reduction factors are calculated for different durations and areas.
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| 3. |
- Berndtsson, Ronny, et al.
(författare)
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Spatial and temporal scales in rainfall analysis : Some aspects and future perspectives
- 1988
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 100:1-3, s. 293-313
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Tidskriftsartikel (refereegranskat)abstract
- Aspects of spatial and temporal rainfall variability and rainfall analysis in relation to some water management problems are surveyed and discussed. It is concluded that relevant modelling of hydrological processes in which the rainfall is a driving force is vital with respect to possibilities of finding solutions to increasing environmental problems following urbanization and industrialization. However, modern computer methods and our knowledge of the spatial and dynamic properties of rainfall fields are seldom used in practical engineering applications. This causes errors and uncertainties in the calculated output. Bridging the gaps between researchers and engineers may overcome some of these problems. It is also argued that experimental studies in a variety of climates and physiographical conditions using an interdisciplinary approach are needed in order to further investigate the scale and dynamics of spatial rainfall variability.
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| 4. |
- Berndtsson, Ronny, et al.
(författare)
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Spatial variability of infiltration in a semi-arid environment
- 1987
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 90:1-2, s. 117-133
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Tidskriftsartikel (refereegranskat)abstract
- Fifty-two double-ring infiltrometer tests, performed in a small, partly urbanized catchment in northern Tunisia are analyzed. Spatial variability is characterized by use of cross-correlation functions. Spatial patterns of infiltration properties are shown to be governed by geomorphology and occurring vegetation. Different geomorphological zones and zones with equal density of vegetation tend to be oriented in a parallel pattern in relation to the wadi. Statistical properties of infiltration capacities depending on geomorphological zone are presented.
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| 5. |
- Zhang, Tielin, et al.
(författare)
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Temporal patterns and spatial scale of soil water variability in a small humid catchment
- 1988
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 104:1-4, s. 111-128
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Tidskriftsartikel (refereegranskat)abstract
- Temporal and spatial variability of soil water content on mainly two different scales is visualized by means of correlation analyses. The soil water data were collected at seven sites for a period of about ten years. The spatial variability of soil water in the unsaturated zone is illustrated and discussed from the aspects of interdepth, intersite and temporal changes respectively. The results in terms of the correlation structure show an increase in spatial variability when depth increases. Three soil layers with different patterns of variability are identified: 0-60, 60-140, and 140-240 cm. It is concluded that the mean time series values of the soil water content do not differ significantly within horizontal distances of about 10-20m. For distances of about 1100m this variation may be more than 5% by volume in absolute values. Higher spatial variability is noted during the summer period (May-September).
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