New empirical models have been developed in this study to facilitate the estimation of global sol... more New empirical models have been developed in this study to facilitate the estimation of global solar radiation for Bahrain from commonly measured meteorological parameters. The objective is to minimize the errors and the number of parameters incorporated in the models over the existing ones. The results obtained are very encouraging. When the estimated values were compared with the measured ones, the models provided very high correlation factors of over 0.99 and absolute maximum errors of only 1.9-7.9%. The best models have been established when the monthly mean daily data were treated at intervals, namely January-June and July-December. These models are dependent on one to three measured inputs, such as temperature, bright sunshine duration, relative humidity and extraterrestrial solar radiation. The present models can, thus, be recommended for the State of Bahrain.
The paper presents regional time series of the standardized precipitation index (SPI) for the ari... more The paper presents regional time series of the standardized precipitation index (SPI) for the arid and semi-arid areas of Sudan during the period 1941-2010. Accordingly, the regional drought events are detected and evaluated for their severity based on two time scales, 3-running months and 12 months. Probability curves of the SPIs have been compared between two periods, wet (1941-1970) and dry (1971-2010). The vulnerability of agriculture to drought is assessed by the relationship between the inter-annual variability in both the crop yield (CY) and the SPI over the time span 1961-2009. Sorghum and millet were chosen as major food crops grown in the region. It has been found that (1) the so-called rainfall recovery period of 1991-2010, though wetter than 1971-1990, has far less wet conditions compared to the pre-drought period, (2) the 2000s have seen at least 2-4 drought years of mild and moderate severities, (3) the drought can occur on seasonal basis with 44-47% probability (retur...
ABSTRACT Understanding the human–water–food–climate nexus is central to achieving sustainable int... more ABSTRACT Understanding the human–water–food–climate nexus is central to achieving sustainable intensification (SI) in agriculture. This research uses a socio-hydrological approach to understand the underpinning for implementing SI in the Gezira Irrigation Scheme, Sudan, by integrating vegetation indices derived from remote sensing, ancillary, gridded soil and precipitation data, supplemented by interviews with 393 farmers. The productivity gap was estimated as the difference between the potential and actual productivities. Based upon data on farmers’ socio-economic status and field practices, a regression tree model was built to determine the factors that control the sorghum yield. The model revealed that the financial status of farmers and access to water are the most influential factors on sorghum yield. A conceptual framework that elucidates SI and its bi-directional feedback to the environment, society and the economy is proposed. Implementing SI in the scheme has implications on water and food security in Sudan and beyond its borders.
Highlights GPCC 7.0 and five satellite-based rainfall products versus station rainfall for Sout... more Highlights GPCC 7.0 and five satellite-based rainfall products versus station rainfall for South Sudan Monthly and annual data from GPCC 7.0 followed by CHIRPS v2.0 agree best with station rainfall Capturing the variability in maximum monthly rainfall is attained best by ARC2 then by GPCC 7.0.
A comparative study of estimating the day-length, S0, and extraterrestrial radiation, H, is condu... more A comparative study of estimating the day-length, S0, and extraterrestrial radiation, H, is conducted, with special reference to Sudan. Due to the definitions of the formulae of Cooper and Hay, differences in S0-values are normal; however, the former formula revealed excellent agreement with data on the duration between sunrise and sunset. Hence, the paper recommends adopting Cooper's method for computing
Résumé/Abstract New empirical models have been developed in this study to facilitate the estimati... more Résumé/Abstract New empirical models have been developed in this study to facilitate the estimation of global solar radiation for Bahrain from commonly measured meteorological parameters. The objective is to minimize the errors and the number of parameters ...
... from 1947 to 2005 Nadir Ahmed Elagib & Anwar S. Addin Abdu ... Qureshi and Khan (1994) re... more ... from 1947 to 2005 Nadir Ahmed Elagib & Anwar S. Addin Abdu ... Qureshi and Khan (1994) reported a shift in average annual temperature at two stations in Riyadh (Saudi Arabia) that could explain a moderate growth of heat island effect. ...
The aims of this paper are twofold: to define the range of principal forms the climate of Bahrain... more The aims of this paper are twofold: to define the range of principal forms the climate of Bahrain has taken during the past six decades, particularly through the temperature and rainfall trends, and to evaluate the consequent degree of aridity on the Islands. The study demonstrates enormous climate variability, represented by alternate hot-dry and cool-wet events. The high temperature level, the scantiness of rainfall and the excessive evapo-transpiration losses are striking phenomena. Using different aridity criteria, Bahrain has been regarded as arid or hyperarid as a result of the highly altering variation in climatic conditions. Continuation of the existing climate status, besides the increasing human interference, would constitute favourable circumstances for aridification to intensify and spread, and hence would likely have significant ecological and economical impacts.
The mean temperature time-series over the period 1941-1996 for 13 stations across Sudan are exami... more The mean temperature time-series over the period 1941-1996 for 13 stations across Sudan are examined on seasonal and annual bases to explore any possible trends in recent decades. Standardized anomaly indices (SAIs), intraannual coefficients of variability, and autocorrelation coefficients are also developed. The consistency of both seasonal and annual patterns is also studied. South of latitude 163N, the data show the tendency for annual time-series to follow mostly the wet-season time-series. The zone located northward is also an exception among other parts, as it does not reveal an actual change in its temperature series towards cooling or warming, but rather shows fluctuations between these two phases. In the rest of the country, a linear fit established for annual temperature series indicates significant upward trends, synchronized with those in wet-and hot-season series; the rising trends in the former seasonal series being higher and more significant. Since the 1940s, annual and wet-season temperatures have increased by 0)076-0)20 and 0)082-0)293C per decade, respectively. The period of greater warmth in Sudan appears to coincide with that of rainfall depletion reported post mid-1960s. A general increase in the coefficient of variability (C v) of the within-year monthly temperatures has also been noticed. This increase is statistically significant in northern and most central locations.
... All rights reserved. Permissions & Reprints. New approaches for estimating global... more ... All rights reserved. Permissions & Reprints. New approaches for estimating global solar radiation across Sudan. Nadir Ahmed Elagib Corresponding Author Contact Information , E-mail The Corresponding Author and Martin G. Mansell. ...
Four mean temperature variables, namely maximum (MAX), minimum (MIN), mean (MEAN) and diurnal tem... more Four mean temperature variables, namely maximum (MAX), minimum (MIN), mean (MEAN) and diurnal temperature range (DTR), were considered for 14 selected observational stations throughout Sudan. The objectives were to investigate the seasonal and annual regimes, the seasonal and annual trends, the intra-annual variability (IAV) by the coefficient of variation (CV), and the interrelationships between the temperature variables and percent of possible sunshine. A mounting evidence of daytime and nighttime warming since the 1940s until 2005 is presented. The exception is the dry season which is dominated by daytime cooling attributable to the damping effect of dust haze/storms. Apparently, the progressive drought across inland locations has raised the MAXs, and to a lesser extent the MINs, of the wet season over those for the hot season. Accordingly, maximum rates of 0.451 and 0.336°C decade-1 were found for the nighttime and daytime temperatures, respectively. The extreme eastern and western locations have been frequently dominated by the warmest trend rates obtained nationwide. The prevalence of significant decreases (increases) of DTR is more apparent in the dry, hot and annual series (wet series). Depending on the temperature variable under consideration, many stations possessed significant trends toward either increased or decreased variability of the within-year monthly values, i.e. IAV. The correlation between the time series of annual CV and extreme values for each of the four temperature variables shows generally that warmer climate in Sudan is associated with higher intra-annual temperature variability and vise versa, i.e. the CV is directly correlated with the highest value within the year, but inversely correlated with the lowest one. The findings of this investigation also indicate that the DTR is directly related to percent of possible sunshine, but the relationship of the latter parameter is not so clear with MAX, MIN and MEAN.
Hydropower energy generation depends on the available water resources. Therefore, planning and op... more Hydropower energy generation depends on the available water resources. Therefore, planning and operation of the water resource systems are paramount tasks for energy management. Since reservoirs are one of the important components of water resources systems, extracting optimal operating policies for proper management of energy generated from these systems is an imperative step. Optimizing reservoir system operation (ORSO) is a non-linear, large-scale, and non-convex problem with a large number of constraints and decision variables. To solve ORSO problem effectively, a robust diversity-based, sine-cosine algorithm (RDB-SCA) is developed in the present study by introducing several strategies to balance the global exploration and local exploitation ability and to achieve accurate and reliable solutions. An efficient linear operation rule is coupled with the RDB-SCA to maximize the energy generation. The proposed method is then applied to a real-world, multi-reservoir system to extract optimal operational policies and, consequently, maximize the energy production. It is shown that the RDB-SCA is able to generate 24, 14, and 6% more energy than the original SCA, respectively for 2-, 3-, and 4-reservoir systems. The present findings are useful to suggest guidelines for efficient operation of hydropower multi-reservoir systems. This paper is supported by https://imanahmadianfar.com/codes.
The Grand Ethiopian Renaissance Dam (GERD) on the Nile River will double Ethiopia’s electricity g... more The Grand Ethiopian Renaissance Dam (GERD) on the Nile River will double Ethiopia’s electricity generation and reduce the Nile flow to Sudan and Egypt during reservoir filling. We argue that multi-country negotiations over the initial filling and long-term operation of the GERD reservoir should not overlook key dam engineering features.
New empirical models have been developed in this study to facilitate the estimation of global sol... more New empirical models have been developed in this study to facilitate the estimation of global solar radiation for Bahrain from commonly measured meteorological parameters. The objective is to minimize the errors and the number of parameters incorporated in the models over the existing ones. The results obtained are very encouraging. When the estimated values were compared with the measured ones, the models provided very high correlation factors of over 0.99 and absolute maximum errors of only 1.9-7.9%. The best models have been established when the monthly mean daily data were treated at intervals, namely January-June and July-December. These models are dependent on one to three measured inputs, such as temperature, bright sunshine duration, relative humidity and extraterrestrial solar radiation. The present models can, thus, be recommended for the State of Bahrain.
The paper presents regional time series of the standardized precipitation index (SPI) for the ari... more The paper presents regional time series of the standardized precipitation index (SPI) for the arid and semi-arid areas of Sudan during the period 1941-2010. Accordingly, the regional drought events are detected and evaluated for their severity based on two time scales, 3-running months and 12 months. Probability curves of the SPIs have been compared between two periods, wet (1941-1970) and dry (1971-2010). The vulnerability of agriculture to drought is assessed by the relationship between the inter-annual variability in both the crop yield (CY) and the SPI over the time span 1961-2009. Sorghum and millet were chosen as major food crops grown in the region. It has been found that (1) the so-called rainfall recovery period of 1991-2010, though wetter than 1971-1990, has far less wet conditions compared to the pre-drought period, (2) the 2000s have seen at least 2-4 drought years of mild and moderate severities, (3) the drought can occur on seasonal basis with 44-47% probability (retur...
ABSTRACT Understanding the human–water–food–climate nexus is central to achieving sustainable int... more ABSTRACT Understanding the human–water–food–climate nexus is central to achieving sustainable intensification (SI) in agriculture. This research uses a socio-hydrological approach to understand the underpinning for implementing SI in the Gezira Irrigation Scheme, Sudan, by integrating vegetation indices derived from remote sensing, ancillary, gridded soil and precipitation data, supplemented by interviews with 393 farmers. The productivity gap was estimated as the difference between the potential and actual productivities. Based upon data on farmers’ socio-economic status and field practices, a regression tree model was built to determine the factors that control the sorghum yield. The model revealed that the financial status of farmers and access to water are the most influential factors on sorghum yield. A conceptual framework that elucidates SI and its bi-directional feedback to the environment, society and the economy is proposed. Implementing SI in the scheme has implications on water and food security in Sudan and beyond its borders.
Highlights GPCC 7.0 and five satellite-based rainfall products versus station rainfall for Sout... more Highlights GPCC 7.0 and five satellite-based rainfall products versus station rainfall for South Sudan Monthly and annual data from GPCC 7.0 followed by CHIRPS v2.0 agree best with station rainfall Capturing the variability in maximum monthly rainfall is attained best by ARC2 then by GPCC 7.0.
A comparative study of estimating the day-length, S0, and extraterrestrial radiation, H, is condu... more A comparative study of estimating the day-length, S0, and extraterrestrial radiation, H, is conducted, with special reference to Sudan. Due to the definitions of the formulae of Cooper and Hay, differences in S0-values are normal; however, the former formula revealed excellent agreement with data on the duration between sunrise and sunset. Hence, the paper recommends adopting Cooper's method for computing
Résumé/Abstract New empirical models have been developed in this study to facilitate the estimati... more Résumé/Abstract New empirical models have been developed in this study to facilitate the estimation of global solar radiation for Bahrain from commonly measured meteorological parameters. The objective is to minimize the errors and the number of parameters ...
... from 1947 to 2005 Nadir Ahmed Elagib & Anwar S. Addin Abdu ... Qureshi and Khan (1994) re... more ... from 1947 to 2005 Nadir Ahmed Elagib & Anwar S. Addin Abdu ... Qureshi and Khan (1994) reported a shift in average annual temperature at two stations in Riyadh (Saudi Arabia) that could explain a moderate growth of heat island effect. ...
The aims of this paper are twofold: to define the range of principal forms the climate of Bahrain... more The aims of this paper are twofold: to define the range of principal forms the climate of Bahrain has taken during the past six decades, particularly through the temperature and rainfall trends, and to evaluate the consequent degree of aridity on the Islands. The study demonstrates enormous climate variability, represented by alternate hot-dry and cool-wet events. The high temperature level, the scantiness of rainfall and the excessive evapo-transpiration losses are striking phenomena. Using different aridity criteria, Bahrain has been regarded as arid or hyperarid as a result of the highly altering variation in climatic conditions. Continuation of the existing climate status, besides the increasing human interference, would constitute favourable circumstances for aridification to intensify and spread, and hence would likely have significant ecological and economical impacts.
The mean temperature time-series over the period 1941-1996 for 13 stations across Sudan are exami... more The mean temperature time-series over the period 1941-1996 for 13 stations across Sudan are examined on seasonal and annual bases to explore any possible trends in recent decades. Standardized anomaly indices (SAIs), intraannual coefficients of variability, and autocorrelation coefficients are also developed. The consistency of both seasonal and annual patterns is also studied. South of latitude 163N, the data show the tendency for annual time-series to follow mostly the wet-season time-series. The zone located northward is also an exception among other parts, as it does not reveal an actual change in its temperature series towards cooling or warming, but rather shows fluctuations between these two phases. In the rest of the country, a linear fit established for annual temperature series indicates significant upward trends, synchronized with those in wet-and hot-season series; the rising trends in the former seasonal series being higher and more significant. Since the 1940s, annual and wet-season temperatures have increased by 0)076-0)20 and 0)082-0)293C per decade, respectively. The period of greater warmth in Sudan appears to coincide with that of rainfall depletion reported post mid-1960s. A general increase in the coefficient of variability (C v) of the within-year monthly temperatures has also been noticed. This increase is statistically significant in northern and most central locations.
... All rights reserved. Permissions & Reprints. New approaches for estimating global... more ... All rights reserved. Permissions & Reprints. New approaches for estimating global solar radiation across Sudan. Nadir Ahmed Elagib Corresponding Author Contact Information , E-mail The Corresponding Author and Martin G. Mansell. ...
Four mean temperature variables, namely maximum (MAX), minimum (MIN), mean (MEAN) and diurnal tem... more Four mean temperature variables, namely maximum (MAX), minimum (MIN), mean (MEAN) and diurnal temperature range (DTR), were considered for 14 selected observational stations throughout Sudan. The objectives were to investigate the seasonal and annual regimes, the seasonal and annual trends, the intra-annual variability (IAV) by the coefficient of variation (CV), and the interrelationships between the temperature variables and percent of possible sunshine. A mounting evidence of daytime and nighttime warming since the 1940s until 2005 is presented. The exception is the dry season which is dominated by daytime cooling attributable to the damping effect of dust haze/storms. Apparently, the progressive drought across inland locations has raised the MAXs, and to a lesser extent the MINs, of the wet season over those for the hot season. Accordingly, maximum rates of 0.451 and 0.336°C decade-1 were found for the nighttime and daytime temperatures, respectively. The extreme eastern and western locations have been frequently dominated by the warmest trend rates obtained nationwide. The prevalence of significant decreases (increases) of DTR is more apparent in the dry, hot and annual series (wet series). Depending on the temperature variable under consideration, many stations possessed significant trends toward either increased or decreased variability of the within-year monthly values, i.e. IAV. The correlation between the time series of annual CV and extreme values for each of the four temperature variables shows generally that warmer climate in Sudan is associated with higher intra-annual temperature variability and vise versa, i.e. the CV is directly correlated with the highest value within the year, but inversely correlated with the lowest one. The findings of this investigation also indicate that the DTR is directly related to percent of possible sunshine, but the relationship of the latter parameter is not so clear with MAX, MIN and MEAN.
Hydropower energy generation depends on the available water resources. Therefore, planning and op... more Hydropower energy generation depends on the available water resources. Therefore, planning and operation of the water resource systems are paramount tasks for energy management. Since reservoirs are one of the important components of water resources systems, extracting optimal operating policies for proper management of energy generated from these systems is an imperative step. Optimizing reservoir system operation (ORSO) is a non-linear, large-scale, and non-convex problem with a large number of constraints and decision variables. To solve ORSO problem effectively, a robust diversity-based, sine-cosine algorithm (RDB-SCA) is developed in the present study by introducing several strategies to balance the global exploration and local exploitation ability and to achieve accurate and reliable solutions. An efficient linear operation rule is coupled with the RDB-SCA to maximize the energy generation. The proposed method is then applied to a real-world, multi-reservoir system to extract optimal operational policies and, consequently, maximize the energy production. It is shown that the RDB-SCA is able to generate 24, 14, and 6% more energy than the original SCA, respectively for 2-, 3-, and 4-reservoir systems. The present findings are useful to suggest guidelines for efficient operation of hydropower multi-reservoir systems. This paper is supported by https://imanahmadianfar.com/codes.
The Grand Ethiopian Renaissance Dam (GERD) on the Nile River will double Ethiopia’s electricity g... more The Grand Ethiopian Renaissance Dam (GERD) on the Nile River will double Ethiopia’s electricity generation and reduce the Nile flow to Sudan and Egypt during reservoir filling. We argue that multi-country negotiations over the initial filling and long-term operation of the GERD reservoir should not overlook key dam engineering features.
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