A Note on Rainfall in the Sudan

Hammer, Richard M.

doi:10.1002/j.1477-8696.1968.tb03059.x

Cited by 6 publications

(3 citation statements)

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“…In South Africa, Harrison (1983) observed the following: only 13% of all rain-days in the Eastern Orange Free State are responsible for 50% of the rainfall and only 27% contributed 75% of the total rainfall, whereas the lowest 50% of all rain-days produce as little as 7% of the rainfall. Similar observations were made elsewhere in the world including Argentina (Olascoaga, 1950), Florida (Riehl, 1949, Philippines (Riehl, 1950), and the Sudan (Hammer, 1968). In this study the following observations were made.…”

Section: Probability Of a Wet Daysupporting

confidence: 80%

The characterisation of rainfall in the arid and semi-arid regions of Ethiopia

Tilahun¹

2007

WSA

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In order to plan effective agricultural and water resource projects, it is necessary to understand the spatial and temporal variability of rainfall. Although it is one of the most drought-hit countries in the world, almost no study has ever been conducted in characterising the rainfall pattern of the arid and semi-arid regions of Ethiopia. In this study, rainfall data of the past 50 years was used to study the basic statistical characteristics of the rainfall of this region. Annual and monthly rainfall was fitted to the theoretical probability distributions and the best distributions describing the data at respective stations were determined. Probability of wet days and dry periods of different durations was determined. It has been found that both annual and monthly rainfall at different stations was described by different probability distributions. There is high variation of rainfall pattern among the stations. Heavier rainfall events are infrequent but they make up a significant percentage of the total rainfall. In arid and semi-arid regions where both the amount and frequency of rainfall occurrence is low, it is essential to take into account the unique rainfall characteristics in such regions.

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Section: Probability Of a Wet Daysupporting

confidence: 80%

The characterisation of rainfall in the arid and semi-arid regions of Ethiopia

Tilahun¹

2007

WSA

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“…The resulting effect on the self-adjusting hydrodynamic functions can only be estimated within narrow operating limits. Hammer [3] pointed out that the assumption of integral mean values represents an oversimplification, because hydrodynamic functions in both gas and liquid phases show strong radially and axially overlapping profiles. If, in addition, solid particles are suspended, further interaction occurs according to their local distribution, due to: -particle density, -particle volume concentration, -particle size, -particle shape, -particle wettability.…”

Section: Measurements With Multi-point Microprobes : 1 Introductionmentioning

confidence: 99%

Measurements with multi‐point microprobes: Effect of suspended solids on the hydrodynamics of bubble columns for application in chemical and biotechnological processes

et al. 1990

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Many experimental studies reveal that suspended solids considerably alter the coalescence behaviour and hydrodynamic functions of two-phase flow. But no systematic efforts have yet been undertaken to separate the effects of different particle properties on local gas hold-up, bubble size and interfacial area gasiliquid. The aim of this paper is to present the local values of these parameters in three-phase fluidized beds of different solids, using miniaturized optical fibre and conductivity needle probes. It is shown that particle concentration, size and, in particular, density are decisive for the change in coalescence behaviour. Ranges of normal (e, > eL) and inverse fluidization (e, < eL) must be distinguished and the flow regime also exerts a strong influence on the interactions between the dispersed phases, the transition point itself being a function of particle properties. For certain combinations of solid parameters, even increased interfacial areas gaslliquid can be observed. This effect is evaluated for different column diameters, between 0.1 and 0.3 m.

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“…The patchy nature of rainfall resulting from m situ growth combined with restricted areas of cloud development is a common characteristic of rainfall in Sudan (Hammer 1972). This may partly explain the rainfall recovery in some parts of the region, such as El Gedaref, Ed Damazin and Nyala.…”

Section: Attribution Of the Observed Trends And Regimesmentioning

confidence: 98%

Assessment of drought across central Sudan using UNEP dryness ratio

Elagib

2009

Hydrology Research

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The objective of this paper is to improve our perception of drought In central Sudan. This has been realized by detailing the changes that occurred in the dryness ratio (rainfall/potential evapotranspiration} of the united Nations Environment Programme (UNEP) during the period 1941-2005. Eight representative stations of the area were selected and their dryness ratios examined on annual and monthly bases. A trend towards intensifying and more recurrent drought has been found. This trend is particularly significant in the arid areas. Statistically significant increase in areal coverage of drought has occurred. Substantial changes took place in the severity and frequency of drought between 1941-1970 and 1971-2005 over the whole area.Moreover, the early to mid-1970s, mid-1980s, early 1990s and early 2000s were determined as common drought years and were among the driest 10 years. The analysis also revealed high and generally increasing inter-annual variability of the dryness ratio. There is not a dominant short-term persistence in the data, as assessed by the lag-one serial correlation coefficient. Early forecast of the moisture condition during the rest of the season could merely be accomplished at small scale in the area. These results indicate that drought in the study area is irregular.

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A Note on Rainfall in the Sudan

Cited by 6 publications

References 0 publications

The characterisation of rainfall in the arid and semi-arid regions of Ethiopia

The characterisation of rainfall in the arid and semi-arid regions of Ethiopia

Measurements with multi‐point microprobes: Effect of suspended solids on the hydrodynamics of bubble columns for application in chemical and biotechnological processes

Assessment of drought across central Sudan using UNEP dryness ratio

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