scholarly journals Vegetation Cover Change Associated With Changes in Hydro-Climatic Variables in Northern Sub-Saharan Africa in Recent Decades.

2021 ◽  
Author(s):  
Faustin Katchele Ogou ◽  
Tertsea Igbawua
Keyword(s):  
Soil Moisture ◽  
Vegetation Cover ◽  
Potential Evapotranspiration ◽  
Kendall Test ◽  
Sub Saharan Africa ◽  
Climatic Variables ◽  
Climatic Data ◽  
High Coverage ◽  
Adaptation Capacity ◽  
Sub Saharan

Abstract The environmental change in Northern Sub-Saharan Africa (NSSA) remains a challenge in relation with hydro-climatic variations and the low adaptation capacity of the region. The present study investigates the vegetation cover (NDVI) change associated with variations in hydro-climatic indicators over the period 1982–2015. The conventional statistical techniques such as the linear and multiple regressions, Mann-Kendall test, Sen’slope and the Pearson’s correlation were employed. The vegetation cover based on vegetation (NDVI) and hydro-climatic data were used. Trends in vegetation cover and hydro-climatic variables had monotonically increased except for the soil moisture that had monotonically decreased in the region. The proportion of significant positive (negative) changes were 46.78% (8.10%), 38.13% (0.34%), 52.12% (0.10%), 82.86% (0.00%) and 10.54% (38.27%) for NDVI, precipitation, potential evapotranspiration, temperature and soil moisture, respectively. The low vegetation dominated the NSSA region with a proportion of about 32% of the total area coverage. The vegetation classes including low coverage, very high coverage, and extreme high coverage exhibited increasing trends. Meanwhile, moderate coverage and high coverage exhibited decreasing trends. The area-averaged precipitation and temperature were positively correlated with the NDVI; however, the area-averaged soil moisture showed negative association with NDVI. Except the precipitation and Significant positive (negative) correlations of NDVI with the precipitation, temperature and soil moisture at the 5% level occupied 1.67% (11.59%), 3.37%(26.19%) and 10.24% (6.75%), respectively. However, the combine effects of hydro-climatic variables are better for the monitoring of vegetation cover. This confirms that the vegetation cover is influenced by many factors.

scholarly journals Estimating Sahelian and East African soil moisture using the Normalized Difference Vegetation Index

2013 ◽  
Vol 10 (6) ◽  
pp. 7963-7997 ◽  
Author(s):  
A. McNally ◽  
C. Funk ◽  
G. J. Husak ◽  
J. Michaelsen ◽  
B. Cappelaere ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Early Warning ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Agricultural Drought ◽  
Sub Saharan Africa ◽  
Sub Saharan ◽  
The Relationship ◽  
African Sahel

Abstract. Rainfall gauge networks in Sub-Saharan Africa are inadequate for assessing Sahelian agricultural drought, hence satellite-based estimates of precipitation and vegetation indices such as the Normalized Difference Vegetation Index (NDVI) provide the main source of information for early warning systems. While it is common practice to translate precipitation into estimates of soil moisture, it is difficult to quantitatively compare precipitation and soil moisture estimates with variations in NDVI. In the context of agricultural drought early warning, this study quantitatively compares rainfall, soil moisture and NDVI using a simple statistical model to translate NDVI values into estimates of soil moisture. The model was calibrated using in-situ soil moisture observations from southwest Niger, and then used to estimate root zone soil moisture across the African Sahel from 2001–2012. We then used these NDVI-soil moisture estimates (NSM) to quantify agricultural drought, and compared our results with a precipitation-based estimate of soil moisture (the Antecedent Precipitation Index, API), calibrated to the same in-situ soil moisture observations. We also used in-situ soil moisture observations in Mali and Kenya to assess performance in other water-limited locations in sub Saharan Africa. The separate estimates of soil moisture were highly correlated across the semi-arid, West and Central African Sahel, where annual rainfall exhibits a uni-modal regime. We also found that seasonal API and NDVI-soil moisture showed high rank correlation with a crop water balance model, capturing known agricultural drought years in Niger, indicating that this new estimate of soil moisture can contribute to operational drought monitoring. In-situ soil moisture observations from Kenya highlighted how the rainfall-driven API needs to be recalibrated in locations with multiple rainy seasons (e.g., Ethiopia, Kenya, and Somalia). Our soil moisture estimates from NDVI, on the other hand, performed well in Niger, Mali and Kenya. This suggests that the NDVI-soil moisture relationship may be more robust across rainfall regimes than the API because the relationship between NDVI and plant available water is less reliant on local characteristics (e.g., infiltration, runoff, evaporation) than the relationship between rainfall and soil moisture.

scholarly journals The Global Trend of the Net Irrigation Water Requirement of Maize from 1960 to 2050

Climate ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 124 ◽  
Author(s):  
Abdoulaye Oumarou Abdoulaye ◽  
Haishen Lu ◽  
Yonghua Zhu ◽  
Yousef Alhaj Hamoud ◽  
Mohamed Sheteiwy
Keyword(s):  
Climate Change ◽  
North America ◽  
Irrigation Water ◽  
Potential Evapotranspiration ◽  
Water Requirement ◽  
Global Climate Models ◽  
Sub Saharan Africa ◽  
Climate Change Scenarios ◽  
Irrigation Water Requirement ◽  
Sub Saharan

Irrigated production around the world has significantly increased over the last decade. However, climate change is a new threat that could seriously aggravate the irrigation water supplies and request. In this study, the data is derived from the IPCC Fifth Assessment Report (AR5). For the climate change scenarios, five Global Climate Models (GCMs) have been used. By using the CROPWAT approach of Smith, the net irrigation water requirement (IRnet) was calculated. For the estimation of the potential evapotranspiration (Epot), the method in Raziei and Pereira was used. According to representative concentration pathway (RCP) 4.5, these increases vary between 0.74% (North America) and 20.92% (North America) while the RCP 8.5 predict increases of 4.06% (sub-Saharan Africa) to more than 68% (North America). The results also show that the region of Latin America is the region with the large amount of IRnet with coprime value between 1.39 km3/yr (GFDL 4.5) and 1.48 km3/yr (CSIRO 4.5) while sub-Saharan Africa has the smallest IRnet amount between 0.13 km3/yr (GFDL 8.5) and 0.14 km3/yr (ECHAM 8.5). However, the most affected countries by this impact are those in sub-Saharan Africa. This study will probably help decision-makers to make corrections in making their decision.

Continental-scale modelling of the effects of climatic and non-climatic disturbances on woody plant encroachment in the grasslands of Africa

2021 ◽  
Author(s):  
Francesco D'Adamo ◽  
Rebecca Spake ◽  
James Bullock ◽  
Booker Ogutu ◽  
Jadunandan Dash ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Woody Plant ◽  
Population Change ◽  
Sub Saharan Africa ◽  
Woody Vegetation ◽  
Woody Plant Encroachment ◽  
Continental Scale ◽  
Wide Range ◽  
Sub Saharan ◽  
Climatic Disturbances

<p>Grasslands cover ca. 7% (2,100,000 km2) of the African continent. They provide a wide range of ecosystem services (e.g., forage, water, recreational spaces, carbon sequestration), and host large wildlife communities. Despite their importance, African grasslands are reported to be suffering from degradation and, perhaps more worryingly, have received little consideration within international policies (e.g., United Nations Sustainable Development Goals). A key issue at present is widespread woody plant encroachment (WPE), which it is shifting African grassland from a grassy- to a (less palatable) woody-dominated biome. However, the way climatic (e.g., precipitation, soil moisture) and non-climatic disturbances (e.g., fire, population density) affect WPE is still poorly understood, particularly at large spatiotemporal scales. Here we identified grasslands in sub-Saharan Africa according to the ESA Climate Change Initiative (CCI) land cover product and use vegetation optical depth (VOD) from passive microwave observations as a proxy for woody vegetation change between 1992 and 2011. We then use independent climatic (precipitation and soil moisture) and non-climatic (burn intensity, population change) data to assess how both spatiotemporal variations and interactions between climatic and non-climatic drivers controlled rates of VOD increase during 1992-2011. We consider not only annual precipitation, soil moisture, fire, and population data, but also integrated and lagged precipitation data (both up to five years ahead of VOD) in these models. Preliminary results reveal a large overall increase in woody vegetation in sub-Saharan Africa grasslands as well as considerable spatiotemporal variation in VOD change that is not due to climatic factors alone.</p>

scholarly journals Spatiotemporal Characteristics and Trend Analysis of two Evapotranspiration-based droughts products and their mechanisms in Sub-Saharan Africa

2020 ◽  
Author(s):  
Isaac Kwesi Nooni ◽  
Daniel Fiifi Tawia Hagan ◽  
Guojie Wang ◽  
Waheed Ullah ◽  
Shijie Li ◽  
...  
Keyword(s):  
Correlation Analysis ◽  
Trend Analysis ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Potential Evapotranspiration ◽  
Mitigation Strategies ◽  
Sub Saharan Africa ◽  
Drought Severity ◽  
Drought Assessment ◽  
Sub Saharan

Drought severity still remains a serious concern across sub-Saharan Africa (SSA) due to the destructive impact on multiple sectors of our society The interannual variability and trends in the changes of self-calibrated Palmer Drought Severity Index based on Penman–Monteith (scPDSIPM) and Thornthwaite (scPDSITH) methods for potential evapotranspiration (PET), precipitation (P) and normalized difference vegetation index (NDVI) anomalies, and sea surface temperature (SST) anomaly were investigated through statistical analysis of modelled and remote sensing data. It is shown that scPDSIPM and scPDSITH differed in the representation of drought characteristics over SSA. The scPDSI and remotely-sensed-based anomalies of P and NDVI showed wetting and drying trends over the period 1980-2012. The trend analysis showed increased drought events in the semi-arid and arid regions of SSA over the same period. A correlation analysis reveals a strong relationship between scPDSI variability and P, and NDVI anomalies for monsoon and pre-monsoon seasons. The correlation analysis of scPDSI variability with SST anomalies indicates significant positive and negative relationships, respectively. This study has demonstrated the applicability of multiple data sources for drought assessment and provides useful information for regional drought predictability and mitigation strategies.

scholarly journals Single nucleotide polymorphism induces divergent dynamic patterns in CYP3A5: a microsecond scale biomolecular simulation of variants identified in Sub-Saharan African populations

2021 ◽  
Author(s):  
Houcemeddine Othman ◽  
Jorge Emanuel Batista da Rocha ◽  
Scott Hazelhurst
Keyword(s):  
Structural Changes ◽  
Rare Variants ◽  
Drug Binding ◽  
Sub Saharan Africa ◽  
High Coverage ◽  
Single Nucleotide ◽  
African Populations ◽  
Sub Saharan ◽  
Dynamics Simulations ◽  
The Impact

Pharmacogenomics aims to reveal variants associated with drug response phenotypes. Genes whose roles involve the absorption, distribution, metabolism, and excretion of drugs, are highly polymorphic between populations. High coverage whole genome sequencing showed that a large proportion of the variants for these genes are rare in African populations. This study investigates the impact of such variants on protein structure to assess their functional importance. We use genetic data of CYP3A5 from 458 individuals from sub-Saharan Africa to conduct a structural bioinformatics analysis. Five missense variants were modeled and microsecond scale molecular dynamics simulations were conducted for each, as well as for the CYP3A5 wildtype, and the Y53C variant, which has a known deleterious impact on enzyme activity. The binding of ritonavir and artemether to CYP3A5 variant structures was also evaluated. Our results showed different conformational characteristics between all the variants. No significant structural changes were noticed. However, the genetic variability acts on the plasticity of the protein. The impact on drug binding may be drug dependant. We conclude that rare variants hold relevance in determining the pharmacogenomics properties of populations. This could have a significant impact on precision medicine applications in sub-Saharan Africa.

scholarly journals Large and persistent subnational inequalities in reproductive, maternal, newborn and child health intervention coverage in sub-Saharan Africa

2020 ◽  
Vol 5 (1) ◽  
pp. e002232 ◽  
Author(s):  
Cheikh Mbacké Faye ◽  
Fernando C Wehrmeister ◽  
Dessalegn Y Melesse ◽  
Martin Kavao Kavao Mutua ◽  
Abdoulaye Maïga ◽  
...  
Keyword(s):  
Child Health ◽  
Health Planning ◽  
Capital City ◽  
Sub Saharan Africa ◽  
High Coverage ◽  
Newborn And Child Health ◽  
Essential Interventions ◽  
Wide Range ◽  
Sub Saharan ◽  
And Child Health

Subnational inequalities have received limited attention in the monitoring of progress towards national and global health targets during the past two decades. Yet, such data are often a critical basis for health planning and monitoring in countries, in support of efforts to reach all with essential interventions. Household surveys provide a rich basis for interventions coverage indicators on reproductive, maternal, newborn and child health (RMNCH) at the country first administrative level (regions or provinces). In this paper, we show the large subnational inequalities that exist in RMNCH coverage within 39 countries in sub-Saharan Africa, using a composite coverage index which has been used extensively by Countdown to 2030 for Women’s, Children’s and Adolescent’s Health. The analyses show the wide range of subnational inequality patterns such as low overall national coverage with very large top inequality involving the capital city, intermediate national coverage with bottom inequality in disadvantaged regions, and high coverage in all regions with little inequality. Even though nearly half of the 34 countries with surveys around 2004 and again around 2015 appear to have been successful in reducing subnational inequalities in RMNCH coverage, the general picture shows persistence of large inequalities between subnational units within many countries. Poor governance and conflict settings were identified as potential contributing factors. Major efforts to reduce within-country inequalities are required to reach all women and children with essential interventions.

MACROCLIMATIC MODEL FOR ESTIMATING MONTHLY SOIL TEMPERATURES UNDER SHORT-GRASS COVER IN CANADA

1973 ◽  
Vol 53 (3) ◽  
pp. 263-274 ◽  
Author(s):  
C. E. OUELLET
Keyword(s):  
Soil Temperature ◽  
Potential Evapotranspiration ◽  
Important Variable ◽  
Climatic Variables ◽  
Standard Errors ◽  
Climatic Data ◽  
Regression Equations ◽  
Grass Cover ◽  
Temperature Variations ◽  
Soil Temperatures

A macroclimatic model was developed to estimate monthly soil temperatures under short-grass cover. It involved multiple regression equations for each month and for each of six depths (1, 10, 20, 50, 100, and 150 cm). Data used were obtained from published records of soil temperature and corresponding climatic variables. They were from 41 stations over several years with station-years per regression varying from 88 to 226 according to depths and months. The climatic variables were related to air temperature, rainfall, snowfall, and potential evapotranspiration. An additional important variable was the estimated soil temperature of the previous month. The equations explain 70–96% of the soil temperature variations and the standard errors of estimate varied from 0.7 to 2.2 C. Temperatures estimated for 1 yr and eight stations with climatic data not used in the development of the equations departed from the observed values by less than 0.5, 1.0, and 2.0 C in 34, 62, and 92% of the cases, respectively. Errors resulting from the estimation of monthly normals by this model are expected to be generally less than 1.0 degree C.

scholarly journals On the Influence of Vegetation Cover Changes and Vegetation-Runoff Systems on the Simulated Summer Potential Evapotranspiration of Tropical Africa Using RegCM4

2021 ◽  
Author(s):  
Samy A. Anwar ◽  
Ossénatou Mamadou ◽  
Ismaila Diallo ◽  
Mouhamadou Bamba Sylla
Keyword(s):  
Soil Moisture ◽  
Vegetation Cover ◽  
Climate Model ◽  
Potential Evapotranspiration ◽  
Regional Climate ◽  
Boreal Summer ◽  
Climatic Research Unit ◽  
Tropical Africa ◽  
Infiltration Capacity ◽  
Community Land Model

AbstractThe community land model version 4.5 provides two ways for treating the vegetation cover changes (a static versus an interactive) and two runoff schemes for tracking the soil moisture changes. In this study, we examined the sensitivity of the simulated boreal summer potential evapotranspiration (PET) to the aforementioned options using a regional climate model. Three different experiments with each one covering 16 years have been performed. The two runoff schemes were designated as SIMTOP (TOP) and variable infiltration capacity (VIC). Both runoff schemes were coupled to the carbon–nitrogen (CN) module, thus the vegetation status can be influenced by soil moisture changes. Results show that vegetation cover changes alone affect considerably the simulated 2-m mean air temperature (T2M). However, they do not affect the global incident solar radiation (RSDS) and PET. Conversely to the vegetation cover changes alone, the vegetation-runoff systems affect both the T2M and RSDS. Therefore, they considerably affect the simulated PET. Also, the CN-VIC overestimates the PET more than the CN-TOP compared to the Climatic Research Unit observational dataset. In comparison with the static vegetation case and CN-VIC, the CN-TOP shows the least bias of the simulated PET. Overall, our results show that the vegetation-runoff system is relevant in constraining the PET, though the CN-TOP can be recommended for future studies concerning the PET of tropical Africa.

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