David Mulati | Jomo Kenyatta University of Agriculture and Technology (original) (raw)
Papers by David Mulati
Journal of Agricultural Science and Technology, Oct 24, 2012
This paper analyzes the suitability of organic dyes (hibiscus, Solanum nigrum, beetroot and eggpl... more This paper analyzes the suitability of organic dyes (hibiscus, Solanum nigrum, beetroot and eggplant) that are locally available in East Africa for low-budget dye sensitized solar cells (DSSC). The natural dyes were extracted in different ways, where the nightshade berries and eggplant were simply crushed and sieved to obtain their juices, while for hibiscus and beetroot, the fruits was boiled in water and then ethanol. The most promising results are found from hibiscus extracted in water at 50˚C, which exhibit a significantly better performance in U mpp (311.35mV), I mpp (236.43A) and efficiency (0.43%). The results also show that Solanum nigrum is strong in terms of voltage but poor in terms of current, while Eggplant fails due to a difficult extraction process. Beetroot turns out to be a poor candidate since it contains betanin which does not chelate to the TiO 2 surface of the cell. The analysis of Solanum nigrum and hibiscus mixture shows that these mixtures do not lead to a better performance. It is also observed that the process of chelating to the TiO 2 shifts the absorption spectra of the dyes slightly towards lower wavelengths. The analysis of the molecular structures of betanin and certain anthocyanins shows the number of =O and-OH groups relative to the total number of atoms per molecule is higher for most anthocyanins, so that they can connect better to TiO 2 than betanin.
Journal of Agricultural Science and Technology, Oct 24, 2014
IEICE technical report. Component parts and materials, May 21, 1998
Journal of Agricultural Science and Technology, 2016
In this work, an improved microcontroller-based maximum power point tracking algorithm for PV sol... more In this work, an improved microcontroller-based maximum power point tracking algorithm for PV solar charge controller is proposed and implemented. The proposed algorithm uses fuzzy logic controller to adaptively modify the step-size of a conventional P&O algorithm, thereby improving its transient and steady-state responses. The proposed algorithm is implemented in a prototype solar charge controller consisting of a solar panel, a buck converter and a microcontroller. The results of the tests performed on the proposed algorithm are compared to those of a conventional P&O algorithm and a PV system with no MPPT, to validate the algorithm. The comparison with the conventional P&O algorithm shows 93% and 72% improvements in transient and steady-state responses, respectively, while that with no MPPT shows 71% improvement in efficiency with which the proposed algorithm extract energy from a solar panel.
Kyoto University (京都大学)0048新制・課程博士博士(工学)甲第7951号工博第1853号新制||工||1152(附属図書館)UT51-99-M256京都大学大学院工学研究科... more Kyoto University (京都大学)0048新制・課程博士博士(工学)甲第7951号工博第1853号新制||工||1152(附属図書館)UT51-99-M256京都大学大学院工学研究科電子物性工学専攻(主査)教授 松波 弘之, 教授 藤田 茂夫, 教授 松重 和美学位規則第4条第1項該
Journal of Agriculture, Science and Technology, 2004
ABSTRACT Samples of 1cm2 sizes were made from the p-type multi-crystalline silicon boron doped 10... more ABSTRACT Samples of 1cm2 sizes were made from the p-type multi-crystalline silicon boron doped 1016cm-3. Aluminium contacts were made in a vacuum of 10-6 Torr and post-annealed in Argon ambient at 400°C for 30 minutes for making the four contact electrodes. The activation energy based on low compensation was found to be 47 meV, 32 meV, and 18 meV, respectively. In order to obtain a more reliable solution, the differential evaluation on the temperature dependence of hole concentration was done. Four peaks were observed around 50, 56, 88, and 109 meV, which indicate several acceptor levels in multi-crystalline silicon (Mx-Si). Hall mobility at 300 K in this p-type sample was 189 (cm2/Vs) and 3231 (cm2/Vs) at 72 K. Based on acoustic phonon scattering the mobility decrease with temperature showed T-1.96 dependence. This behavior indicates the inter-valley scattering as well as grain boundary effects.KEY WORDS: Compensation, multi-crystalline silicon, activation energy, mobility, grain boundariesJ. agric. Sci. technol. Vol.5(1) 2003: 106-115
IntechOpen eBooks, Nov 14, 2022
The energy conversion efficiency and limits of perovskite/silicon solar cells are investigated. T... more The energy conversion efficiency and limits of perovskite/silicon solar cells are investigated. The influence of a layered approach in preventing lead leakage in perovskite solar cells is discussed. The highest efficiency perovskite tandem to date was achieved by pairing a perovskite top cell with a Si bottom cell in a four-terminal configuration, yielding 26.4%. Perovskite cell integrated with crystalline silicon cell to form a tandem solar device has shown high performance above the single pn-junction silicon devices. Although sufficient work and different strategies have been applied to increase efficiency in these devices, the tandem application has achieved efficiency of 29% in a short period.
The main factor that determines the weather and climate on the surface of the earth is the time v... more The main factor that determines the weather and climate on the surface of the earth is the time variation of the position of the overhead sun. This single factor determines the time of the day or night, variation of earth‘s surface temperature, prevailing wind direction and therefore precipitation, weather and climate. The locus of the overhead sun as described by the solar-declination from a reference point on the earth surface can be accurately calculated astronomically at all times. This makes it possible to predict most weather parameters, using weather and climate models. We have in this study used a second important factor to account for the natural climate variability as the time variation of the overhead moon as described in a similar manner by the lunar declination. This study demonstrates that the presence of enhanced atmospheric tides resulting from lunar-solar geometry is a key factor when used to predict the temporal distribution of rainfall amounts. Solar and lunar dec...
South African Journal of Science, 2014
Following NASA’s prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now in... more Following NASA’s prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now include sunspot numbers as an explanatory variable in a statistical model. This model is based on fitting monthly rainfall values with factors and covariates obtained from solar–lunar geometry values and sunspot numbers. The model demonstrates high predictive skill in estimating monthly values by achieving a correlation coefficient of 0.9 between model estimates and the measurements. Estimates for monthly total rainfall for the period from 1901 to 2020 for Kenya indicate that the model can be used not only to estimate historical values of rainfall, but also to predict monthly total rainfall. We have found that the 11-year solar sunspot cycle has an influence on the frequency and timing of extreme hydrology events in Kenya, with these events occurring every 5±2 years after the turning points of sunspot cycles. While solar declination is the major driver of monthly variability, sunspots and ...
A Thesis Presented to Kenyatta University, in Partial/Fulfillment of the Requirement for the Degr... more A Thesis Presented to Kenyatta University, in Partial/Fulfillment of the Requirement for the Degree of Master of Science in Physics. October, 1989.
A comparative study of dye sensitized solar cell (DSSC), one with a magnet and the other without ... more A comparative study of dye sensitized solar cell (DSSC), one with a magnet and the other without a magnet, has been carried out. The current (I)-voltage (V) characteristics of the cells have been determined. For the cell with a magnet, the short circuit current density (JSC) = 8.5 mA/cm 2 , open circuit voltage (VOC) = 0.7 V, fill factor (FF) = 46.6% and efficiency (ƞ) =2.82%. For the cell without a magnet, JSC = 10.58 mA/cm 2 , VOC = 0.7 V, FF = 42.9% and (ƞ) =3.18% Therefore, Nd-Fe-B magnet directly affects the performance of the solar cell. The cells were continually exposed to sunlight after fabrication for 90 days and their long term stability studied. Though the photovoltaic performance of both cells reduced with time, the cell sealed with magnets recorded a better stability
A variety of solar energy systems have been designed to harness sun power to produce both thermal... more A variety of solar energy systems have been designed to harness sun power to produce both thermal and electric energy. Hybrid photovoltaic /thermal (PV/T) solar systems can concurrently provide electric energy and heat, thereby ensuring a higher conversion rate of the absorbed solar radiation. With proper designing, the PV/T systems can minimize the temperature effects on efficiency of a PV module by cooling it. In this paper, we present TRNSYS simulation results for a hybrid PV/T system for domestic water applications for a typical Kenyan family of five. Further, the results of the constructed PV/T system as predicted by the simulations are outlined and discussed. The PV/T system was constructed from polycrystalline silicon module available in the Kenyan market and coupled with water heat extraction unit. The resultant PV/T system was found to meet 47% of the hot water demand for family of five. With a payback period of 5.2 years, the PV/T system gives a lifetime cost saving of abo...
We have done an analysis of the root mean square roughness (RMS) of microcrystalline silicon (c-... more We have done an analysis of the root mean square roughness (RMS) of microcrystalline silicon (c-Si) thin films grown by aluminium induced crystallization (AIC) using Scanning Probe Image Processor software (SPIP). Surface roughness profiles from Dektak 3030 step profiler and topography images from atomic force microscope were loaded into SPIP software. These profiles and images were from films grown at different annealing temperatures. Microcrystalline silicon by aluminium induced crystallization (AIC) is usually used as a seed layer for further epitaxial thickening using methods such as hot wire chemical vapour deposition and ion assisted deposition. The seed layer surface should therefore be smooth for its material properties to be transferred to the epitaxial layer. Films were found to have the largest root mean square roughness at about 470 C in both measurements. A temperature range of 340-420 C has been suggested for the growth of AIC seed layer that can give intermediate r...
Aluminium induced crystallization (AIC) was used to crystallize sputtered amorphous silicon thin ... more Aluminium induced crystallization (AIC) was used to crystallize sputtered amorphous silicon thin films on aluminium-coated glass substrates at annealing temperatures ranging from 250-520°C in vacuum. Crystalline volume fractions were measured by Raman spectrometer as a function of annealing temperature. It was shown that the crystallized films had large grains as the Raman peaks were centred at about 520 cm-1 at and over annealing temperatures of 420°C. The three-layer sample crystallizations resulted in crystallization of the films at lower temperatures compared to the two-layer sample crystallizations which implied a reduction in the cost of production of the seedlayer and resulting products. Hall mobilities and hole densities ranging from 17.0-22.8 cm2V-1s-1and (4.7-9.2) × 1018 cm-3 respectively were measured. Low hole charge densities for films of the same thickness were achieved at high annealing temperatures which was an indication of less aluminium in seed layers prepared at ...
This paper focuses on the area of remote solar home system metering in an effort to bridge solar ... more This paper focuses on the area of remote solar home system metering in an effort to bridge solar energy management in the industry with information technology (IT). A wireless platform was designed using ordinary mobile phone handsets to relay real time digital metering data from a remote PV solar home system via a GSM short message services to a central server (private computer). Here, we experimentally demonstrate the concept of a wireless data transmission of digital direct current (DC) metering data, based on simple and cost‐effective telecommunication technologies through programmed microcontroller circuits that connects to two mobile phones (client and server sets). A set of data was obtained through direct cable connection (meter‐adaptor‐PC) and also through wireless connection (meter‐GSM‐adaptor‐PC). The microcontroller at the server end extracted and decoded data from the received SMS (for wireless connection) and relayed the data to the data adaptor. The applications softw...
South African Journal of Science, 2014
Following NASA's prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now in... more Following NASA's prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now include sunspot numbers as an explanatory variable in a statistical model. This model is based on fitting monthly rainfall values with factors and covariates obtained from solar-lunar geometry values and sunspot numbers. The model demonstrates high predictive skill in estimating monthly values by achieving a correlation coefficient of 0.9 between model estimates and the measurements. Estimates for monthly total rainfall for the period from 1901 to 2020 for Kenya indicate that the model can be used not only to estimate historical values of rainfall, but also to predict monthly total rainfall. We have found that the 11-year solar sunspot cycle has an influence on the frequency and timing of extreme hydrology events in Kenya, with these events occurring every 5±2 years after the turning points of sunspot cycles. While solar declination is the major driver of monthly variability, sunspots and the lunar declinations play a role in the annual variability and may have influenced the occurrence of the Sahelian drought of the mid-1980s that affected the Sahel region including the Greater Horn of Africa. Judging from the reflection symmetry, the trend of the current maximum and the turning point of the sunspot minimum at the end of the Modern Maximum, with a 95% level of confidence, drought conditions similar to those of the early 1920s may reoccur in the year 2020±2.
The main factor that determines the weather on the surface of the earth is the time variation of ... more The main factor that determines the weather on the surface of the earth is the time variation of the position overhead sun. This single factor determines the time of the day or night, variation of the surface temperature, prevailing wind direction and therefore, precipitation, weather and climate at any location on the earth surface. The locus of this position can
A predictive rainfall model based on fitting a Generalized Linear Model on monthly rainfall amoun... more A predictive rainfall model based on fitting a Generalized Linear Model on monthly rainfall amounts with factors and covariates that determine the occurrence and persistence of the gravitational atmospheric tide state is presented. The model demonstrates high skill while estimating monthly amounts by achieving a correlation coefficient above 0.7 between the estimates and the measurements. Model estimates of annual total for the period 1901 to 2020 indicate that the model may not only be used to estimate historical values of rainfall but also predict monthly rainfall amounts. The advantage of atmospheric tidal factors and their derivatives is that their future values are obtained accurately in advance.
Journal of Agricultural Science and Technology, Oct 24, 2012
This paper analyzes the suitability of organic dyes (hibiscus, Solanum nigrum, beetroot and eggpl... more This paper analyzes the suitability of organic dyes (hibiscus, Solanum nigrum, beetroot and eggplant) that are locally available in East Africa for low-budget dye sensitized solar cells (DSSC). The natural dyes were extracted in different ways, where the nightshade berries and eggplant were simply crushed and sieved to obtain their juices, while for hibiscus and beetroot, the fruits was boiled in water and then ethanol. The most promising results are found from hibiscus extracted in water at 50˚C, which exhibit a significantly better performance in U mpp (311.35mV), I mpp (236.43A) and efficiency (0.43%). The results also show that Solanum nigrum is strong in terms of voltage but poor in terms of current, while Eggplant fails due to a difficult extraction process. Beetroot turns out to be a poor candidate since it contains betanin which does not chelate to the TiO 2 surface of the cell. The analysis of Solanum nigrum and hibiscus mixture shows that these mixtures do not lead to a better performance. It is also observed that the process of chelating to the TiO 2 shifts the absorption spectra of the dyes slightly towards lower wavelengths. The analysis of the molecular structures of betanin and certain anthocyanins shows the number of =O and-OH groups relative to the total number of atoms per molecule is higher for most anthocyanins, so that they can connect better to TiO 2 than betanin.
Journal of Agricultural Science and Technology, Oct 24, 2014
IEICE technical report. Component parts and materials, May 21, 1998
Journal of Agricultural Science and Technology, 2016
In this work, an improved microcontroller-based maximum power point tracking algorithm for PV sol... more In this work, an improved microcontroller-based maximum power point tracking algorithm for PV solar charge controller is proposed and implemented. The proposed algorithm uses fuzzy logic controller to adaptively modify the step-size of a conventional P&O algorithm, thereby improving its transient and steady-state responses. The proposed algorithm is implemented in a prototype solar charge controller consisting of a solar panel, a buck converter and a microcontroller. The results of the tests performed on the proposed algorithm are compared to those of a conventional P&O algorithm and a PV system with no MPPT, to validate the algorithm. The comparison with the conventional P&O algorithm shows 93% and 72% improvements in transient and steady-state responses, respectively, while that with no MPPT shows 71% improvement in efficiency with which the proposed algorithm extract energy from a solar panel.
Kyoto University (京都大学)0048新制・課程博士博士(工学)甲第7951号工博第1853号新制||工||1152(附属図書館)UT51-99-M256京都大学大学院工学研究科... more Kyoto University (京都大学)0048新制・課程博士博士(工学)甲第7951号工博第1853号新制||工||1152(附属図書館)UT51-99-M256京都大学大学院工学研究科電子物性工学専攻(主査)教授 松波 弘之, 教授 藤田 茂夫, 教授 松重 和美学位規則第4条第1項該
Journal of Agriculture, Science and Technology, 2004
ABSTRACT Samples of 1cm2 sizes were made from the p-type multi-crystalline silicon boron doped 10... more ABSTRACT Samples of 1cm2 sizes were made from the p-type multi-crystalline silicon boron doped 1016cm-3. Aluminium contacts were made in a vacuum of 10-6 Torr and post-annealed in Argon ambient at 400°C for 30 minutes for making the four contact electrodes. The activation energy based on low compensation was found to be 47 meV, 32 meV, and 18 meV, respectively. In order to obtain a more reliable solution, the differential evaluation on the temperature dependence of hole concentration was done. Four peaks were observed around 50, 56, 88, and 109 meV, which indicate several acceptor levels in multi-crystalline silicon (Mx-Si). Hall mobility at 300 K in this p-type sample was 189 (cm2/Vs) and 3231 (cm2/Vs) at 72 K. Based on acoustic phonon scattering the mobility decrease with temperature showed T-1.96 dependence. This behavior indicates the inter-valley scattering as well as grain boundary effects.KEY WORDS: Compensation, multi-crystalline silicon, activation energy, mobility, grain boundariesJ. agric. Sci. technol. Vol.5(1) 2003: 106-115
IntechOpen eBooks, Nov 14, 2022
The energy conversion efficiency and limits of perovskite/silicon solar cells are investigated. T... more The energy conversion efficiency and limits of perovskite/silicon solar cells are investigated. The influence of a layered approach in preventing lead leakage in perovskite solar cells is discussed. The highest efficiency perovskite tandem to date was achieved by pairing a perovskite top cell with a Si bottom cell in a four-terminal configuration, yielding 26.4%. Perovskite cell integrated with crystalline silicon cell to form a tandem solar device has shown high performance above the single pn-junction silicon devices. Although sufficient work and different strategies have been applied to increase efficiency in these devices, the tandem application has achieved efficiency of 29% in a short period.
The main factor that determines the weather and climate on the surface of the earth is the time v... more The main factor that determines the weather and climate on the surface of the earth is the time variation of the position of the overhead sun. This single factor determines the time of the day or night, variation of earth‘s surface temperature, prevailing wind direction and therefore precipitation, weather and climate. The locus of the overhead sun as described by the solar-declination from a reference point on the earth surface can be accurately calculated astronomically at all times. This makes it possible to predict most weather parameters, using weather and climate models. We have in this study used a second important factor to account for the natural climate variability as the time variation of the overhead moon as described in a similar manner by the lunar declination. This study demonstrates that the presence of enhanced atmospheric tides resulting from lunar-solar geometry is a key factor when used to predict the temporal distribution of rainfall amounts. Solar and lunar dec...
South African Journal of Science, 2014
Following NASA’s prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now in... more Following NASA’s prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now include sunspot numbers as an explanatory variable in a statistical model. This model is based on fitting monthly rainfall values with factors and covariates obtained from solar–lunar geometry values and sunspot numbers. The model demonstrates high predictive skill in estimating monthly values by achieving a correlation coefficient of 0.9 between model estimates and the measurements. Estimates for monthly total rainfall for the period from 1901 to 2020 for Kenya indicate that the model can be used not only to estimate historical values of rainfall, but also to predict monthly total rainfall. We have found that the 11-year solar sunspot cycle has an influence on the frequency and timing of extreme hydrology events in Kenya, with these events occurring every 5±2 years after the turning points of sunspot cycles. While solar declination is the major driver of monthly variability, sunspots and ...
A Thesis Presented to Kenyatta University, in Partial/Fulfillment of the Requirement for the Degr... more A Thesis Presented to Kenyatta University, in Partial/Fulfillment of the Requirement for the Degree of Master of Science in Physics. October, 1989.
A comparative study of dye sensitized solar cell (DSSC), one with a magnet and the other without ... more A comparative study of dye sensitized solar cell (DSSC), one with a magnet and the other without a magnet, has been carried out. The current (I)-voltage (V) characteristics of the cells have been determined. For the cell with a magnet, the short circuit current density (JSC) = 8.5 mA/cm 2 , open circuit voltage (VOC) = 0.7 V, fill factor (FF) = 46.6% and efficiency (ƞ) =2.82%. For the cell without a magnet, JSC = 10.58 mA/cm 2 , VOC = 0.7 V, FF = 42.9% and (ƞ) =3.18% Therefore, Nd-Fe-B magnet directly affects the performance of the solar cell. The cells were continually exposed to sunlight after fabrication for 90 days and their long term stability studied. Though the photovoltaic performance of both cells reduced with time, the cell sealed with magnets recorded a better stability
A variety of solar energy systems have been designed to harness sun power to produce both thermal... more A variety of solar energy systems have been designed to harness sun power to produce both thermal and electric energy. Hybrid photovoltaic /thermal (PV/T) solar systems can concurrently provide electric energy and heat, thereby ensuring a higher conversion rate of the absorbed solar radiation. With proper designing, the PV/T systems can minimize the temperature effects on efficiency of a PV module by cooling it. In this paper, we present TRNSYS simulation results for a hybrid PV/T system for domestic water applications for a typical Kenyan family of five. Further, the results of the constructed PV/T system as predicted by the simulations are outlined and discussed. The PV/T system was constructed from polycrystalline silicon module available in the Kenyan market and coupled with water heat extraction unit. The resultant PV/T system was found to meet 47% of the hot water demand for family of five. With a payback period of 5.2 years, the PV/T system gives a lifetime cost saving of abo...
We have done an analysis of the root mean square roughness (RMS) of microcrystalline silicon (c-... more We have done an analysis of the root mean square roughness (RMS) of microcrystalline silicon (c-Si) thin films grown by aluminium induced crystallization (AIC) using Scanning Probe Image Processor software (SPIP). Surface roughness profiles from Dektak 3030 step profiler and topography images from atomic force microscope were loaded into SPIP software. These profiles and images were from films grown at different annealing temperatures. Microcrystalline silicon by aluminium induced crystallization (AIC) is usually used as a seed layer for further epitaxial thickening using methods such as hot wire chemical vapour deposition and ion assisted deposition. The seed layer surface should therefore be smooth for its material properties to be transferred to the epitaxial layer. Films were found to have the largest root mean square roughness at about 470 C in both measurements. A temperature range of 340-420 C has been suggested for the growth of AIC seed layer that can give intermediate r...
Aluminium induced crystallization (AIC) was used to crystallize sputtered amorphous silicon thin ... more Aluminium induced crystallization (AIC) was used to crystallize sputtered amorphous silicon thin films on aluminium-coated glass substrates at annealing temperatures ranging from 250-520°C in vacuum. Crystalline volume fractions were measured by Raman spectrometer as a function of annealing temperature. It was shown that the crystallized films had large grains as the Raman peaks were centred at about 520 cm-1 at and over annealing temperatures of 420°C. The three-layer sample crystallizations resulted in crystallization of the films at lower temperatures compared to the two-layer sample crystallizations which implied a reduction in the cost of production of the seedlayer and resulting products. Hall mobilities and hole densities ranging from 17.0-22.8 cm2V-1s-1and (4.7-9.2) × 1018 cm-3 respectively were measured. Low hole charge densities for films of the same thickness were achieved at high annealing temperatures which was an indication of less aluminium in seed layers prepared at ...
This paper focuses on the area of remote solar home system metering in an effort to bridge solar ... more This paper focuses on the area of remote solar home system metering in an effort to bridge solar energy management in the industry with information technology (IT). A wireless platform was designed using ordinary mobile phone handsets to relay real time digital metering data from a remote PV solar home system via a GSM short message services to a central server (private computer). Here, we experimentally demonstrate the concept of a wireless data transmission of digital direct current (DC) metering data, based on simple and cost‐effective telecommunication technologies through programmed microcontroller circuits that connects to two mobile phones (client and server sets). A set of data was obtained through direct cable connection (meter‐adaptor‐PC) and also through wireless connection (meter‐GSM‐adaptor‐PC). The microcontroller at the server end extracted and decoded data from the received SMS (for wireless connection) and relayed the data to the data adaptor. The applications softw...
South African Journal of Science, 2014
Following NASA's prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now in... more Following NASA's prediction of sunspot numbers for the current sunspot cycle, Cycle 24, we now include sunspot numbers as an explanatory variable in a statistical model. This model is based on fitting monthly rainfall values with factors and covariates obtained from solar-lunar geometry values and sunspot numbers. The model demonstrates high predictive skill in estimating monthly values by achieving a correlation coefficient of 0.9 between model estimates and the measurements. Estimates for monthly total rainfall for the period from 1901 to 2020 for Kenya indicate that the model can be used not only to estimate historical values of rainfall, but also to predict monthly total rainfall. We have found that the 11-year solar sunspot cycle has an influence on the frequency and timing of extreme hydrology events in Kenya, with these events occurring every 5±2 years after the turning points of sunspot cycles. While solar declination is the major driver of monthly variability, sunspots and the lunar declinations play a role in the annual variability and may have influenced the occurrence of the Sahelian drought of the mid-1980s that affected the Sahel region including the Greater Horn of Africa. Judging from the reflection symmetry, the trend of the current maximum and the turning point of the sunspot minimum at the end of the Modern Maximum, with a 95% level of confidence, drought conditions similar to those of the early 1920s may reoccur in the year 2020±2.
The main factor that determines the weather on the surface of the earth is the time variation of ... more The main factor that determines the weather on the surface of the earth is the time variation of the position overhead sun. This single factor determines the time of the day or night, variation of the surface temperature, prevailing wind direction and therefore, precipitation, weather and climate at any location on the earth surface. The locus of this position can
A predictive rainfall model based on fitting a Generalized Linear Model on monthly rainfall amoun... more A predictive rainfall model based on fitting a Generalized Linear Model on monthly rainfall amounts with factors and covariates that determine the occurrence and persistence of the gravitational atmospheric tide state is presented. The model demonstrates high skill while estimating monthly amounts by achieving a correlation coefficient above 0.7 between the estimates and the measurements. Model estimates of annual total for the period 1901 to 2020 indicate that the model may not only be used to estimate historical values of rainfall but also predict monthly rainfall amounts. The advantage of atmospheric tidal factors and their derivatives is that their future values are obtained accurately in advance.