scholarly journals Statistical Connection between the Madden–Julian Oscillation and Large Daily Precipitation Events in West Africa

2017 ◽  
Vol 30 (6) ◽  
pp. 1999-2010 ◽  
Author(s):  
Awolou Sossa ◽  
Brant Liebmann ◽  
Ileana Bladé ◽  
Dave Allured ◽  
Harry H. Hendon ◽  
...  
Keyword(s):  
West Africa ◽  
Daily Precipitation ◽  
Statistical Tests ◽  
West African ◽  
Seasonal Precipitation ◽  
Madden Julian Oscillation ◽  
Wet Season ◽  
Precipitation Regime ◽  
The Impact ◽  
Precipitation Events

Abstract This study focuses on the impact of the Madden–Julian oscillation (MJO)—as monitored by a well-known multivariate index—on large daily precipitation events in West Africa for the period 1981–2014. Two seasons are considered: the near-equatorial wet season in March–May (MAM) and the peak of the West African monsoon during July–September (JAS), when the intertropical convergence zone (ITCZ) is at its most northerly position. Although the MJO-related interannual variation of seasonal mean rainfall is large, the focus here is on the impacts of the MJO on daily time scales because variations in the frequency of intense, short-term, flood-causing, rainfall events are more important for West African agriculture than variations in seasonal precipitation, particularly near the Guinean coast, where precipitation is abundant. Using composites based on thresholds of daily precipitation amounts, changes in mean precipitation and frequency of the heaviest daily events associated with the phase of the MJO are investigated. The expected modulation of mean rainfall by the MJO is much stronger during MAM than during JAS; yet the modulation of the largest events (i.e., daily rainfall rates above the 90th percentile) is comparable in both seasons. Conservative statistical tests of local and field significance indicate unambiguous impacts of the MJO of the expected sign during certain phases, but the nature of the impact depends on the local seasonal precipitation regime. For instance, in JAS, the early stages of the MJO increase the risk of flooding in the Sahel monsoon region while providing relief to the dry southern coast.

scholarly journals ENSO and Wintertime Extreme Precipitation Events over the Contiguous United States

2008 ◽  
Vol 21 (1) ◽  
pp. 22-39 ◽  
Author(s):  
Siegfried D. Schubert ◽  
Yehui Chang ◽  
Max J. Suarez ◽  
Philip J. Pegion
Keyword(s):  
United States ◽  
West Coast ◽  
Extreme Precipitation ◽  
East Coast ◽  
Daily Precipitation ◽  
Precipitation Variability ◽  
The West ◽  
Extreme Precipitation Events ◽  
The Impact ◽  
Precipitation Events

Abstract In this study the authors examine the impact of El Niño–Southern Oscillation (ENSO) on precipitation events over the continental United States using 49 winters (1949/50–1997/98) of daily precipitation observations and NCEP–NCAR reanalyses. The results are compared with those from an ensemble of nine atmospheric general circulation model (AGCM) simulations forced with observed SST for the same time period. Empirical orthogonal functions (EOFs) of the daily precipitation fields together with compositing techniques are used to identify and characterize the weather systems that dominate the winter precipitation variability. The time series of the principal components (PCs) associated with the leading EOFs are analyzed using generalized extreme value (GEV) distributions to quantify the impact of ENSO on the intensity of extreme precipitation events. The six leading EOFs of the observations are associated with major winter storm systems and account for more than 50% of the daily precipitation variability along the West Coast and over much of the eastern part of the country. Two of the leading EOFs (designated GC for Gulf Coast and EC for East Coast) together represent cyclones that develop in the Gulf of Mexico and occasionally move and/or redevelop along the East Coast producing large amounts of precipitation over much of the southern and eastern United States. Three of the leading EOFs represent storms that hit different sections of the West Coast (designated SW for Southwest coast, WC for the central West Coast, and NW for northwest coast), while another represents storms that affect the Midwest (designated by MW). The winter maxima of several of the leading PCs are significantly impacted by ENSO such that extreme GC, EC, and SW storms that occur on average only once every 20 years (20-yr storms) would occur on average in half that time under sustained El Niño conditions. In contrast, under La Niña conditions, 20-yr GC and EC storms would occur on average about once in 30 years, while there is little impact of La Niña on the intensity of the SW storms. The leading EOFs from the model simulations and their connections to ENSO are for the most part quite realistic. The model, in particular, does very well in simulating the impact of ENSO on the intensity of EC and GC storms. The main model discrepancies are the lack of SW storms and an overall underestimate of the daily precipitation variance.

scholarly journals A Synoptic Review of Forestry and Forest Products Trade and Production in Africa- The Case of Wood and Non-Wood Forest Products in West Africa

2022 ◽  
Author(s):  
John Adekunle Adesina ◽  
Zhu Jiangang ◽  
Tang Xiaolan
Keyword(s):  
West Africa ◽  
Natural Capital ◽  
Natural Habitat ◽  
Forest Products ◽  
West African ◽  
Warning Signs ◽  
Low Carbon ◽  
Forest Reserves ◽  
Impact Reduction ◽  
The Impact

According to this study, approximately half of Africa's forests are utilized primarily or partially for the production of wood and non-wood commodities. Aims to evaluate Africa's forestry and forest products, namely Wood Forest Products (WFPs) and Non-wood Forest Products (NWFPs) in the sixteen (16) West African countries. While adhering to the following guidelines: wood extraction and preparation, analyzing wood primarily used as an energy source in Africa, identifying non-wood forest products in Africa, the state of export, trade, and customs procedures in West Africa, and examining the role of forests and forest stakeholders in Africa's low-carbon economy transition. An exploratory literature review of selected wood forest products and non-wood forest products (plants and animals) in West Africa identifying the country, the natural land area with the natural habitat issues of the forest, the species most harvested and traded in the West African sub-region. The study reemphasized some government legislation, policies, and market trade failures and limitations while also stating that trees may help in the low-carbon revolution through interventions aimed at maintaining, improving, and restoring natural capital have demonstrated that high environmental requirements of sustainable forest management (SFM) may be met in both natural and planted forests. The study identified a systematic assessment of the most common forest products (wood and non-wood forest products) considering the available data on the national forest reserves of the selected countries in West Africa. The study also revealed the need for biodiversity conservation of the available forest reserves to help mitigate the impact of global warming targeting the United Nation’s Sustainable Development Goal 13- Climate Action. Which is focused on integrating climate change mitigation, adaptation, impact reduction, and early warning signs into the national policies, improving forest planning and management education, awareness-raising, and institutional capacity within the sub-region.

scholarly journals Modeling gas exchange and biomass production in West African Sahelian and Sudanian ecological zones

2021 ◽  
Vol 14 (6) ◽  
pp. 3789-3812
Author(s):  
Jaber Rahimi ◽  
Expedit Evariste Ago ◽  
Augustine Ayantunde ◽  
Sina Berger ◽  
Jan Bogaert ◽  
...  
Keyword(s):  
Land Use ◽  
West Africa ◽  
Aboveground Biomass ◽  
Carbon Stocks ◽  
West African ◽  
Biogeochemical Model ◽  
Area Index ◽  
Wide Range ◽  
The Impact ◽  
Mean Square Errors

Abstract. West African Sahelian and Sudanian ecosystems provide essential services to people and also play a significant role within the global carbon cycle. However, climate and land use are dynamically changing, and uncertainty remains with respect to how these changes will affect the potential of these regions to provide food and fodder resources or how they will affect the biosphere–atmosphere exchange of CO2. In this study, we investigate the capacity of a process-based biogeochemical model, LandscapeDNDC, to simulate net ecosystem exchange (NEE) and aboveground biomass of typical managed and natural Sahelian and Sudanian savanna ecosystems. In order to improve the simulation of phenology, we introduced soil-water availability as a common driver of foliage development and productivity for all of these systems. The new approach was tested by using a sample of sites (calibration sites) that provided NEE from flux tower observations as well as leaf area index data from satellite images (MODIS, MODerate resolution Imaging Spectroradiometer). For assessing the simulation accuracy, we applied the calibrated model to 42 additional sites (validation sites) across West Africa for which measured aboveground biomass data were available. The model showed good performance regarding biomass of crops, grass, or trees, yielding correlation coefficients of 0.82, 0.94, and 0.77 and root-mean-square errors of 0.15, 0.22, and 0.12 kg m−2, respectively. The simulations indicate aboveground carbon stocks of up to 0.17, 0.33, and 0.54 kg C ha−1 m−2 for agricultural, savanna grasslands, and savanna mixed tree–grassland sites, respectively. Carbon stocks and exchange rates were particularly correlated with the abundance of trees, and grass biomass and crop yields were higher under more humid climatic conditions. Our study shows the capability of LandscapeDNDC to accurately simulate carbon balances in natural and agricultural ecosystems in semiarid West Africa under a wide range of conditions; thus, the model could be used to assess the impact of land-use and climate change on the regional biomass productivity.

From Sail to Steam: the Impact of the Steamship Services on the British Palm Oil Trade with West Africa, 1850–1890.

1989 ◽  
Vol 30 (2) ◽  
pp. 227-245 ◽  
Author(s):  
Martin Lynn
Keyword(s):  
Nineteenth Century ◽  
West Africa ◽  
Palm Oil ◽  
West African ◽  
Late Nineteenth Century ◽  
The West ◽  
Important Impact ◽  
Late Nineteenth ◽  
The Impact

In the late nineteenth century the West African palm oil trade entered a period of difficulties, characterized mainly by a fall in prices from the early 1860s. Part of the reason for this lay in the introduction of regular steamship services between Britain and West Africa from 1852. As steam came to replace sail so the palm oil trade underwent major changes. These changes can be quantified fairly precisely. One effect of the introduction of steamers was the concentration of the British side of the oil trade once again on Liverpool, its original centre. Another effect was the increase in the number of West African ports involved in the trade. The most important impact was the increase in numbers of traders in oil trade from around 25 to some 150. The resulting increased competition in the trade led to amal-gamations becoming increasingly common – a process that culminated in the formation of the African Association Ltd in 1889. It was also to provide the context for the pressure exerted by some traders for an increased colonial presence in the 1880s and 1890s.

Rethinking the Impact of Structural Adjustment Programs on Human Rights Violations in West Africa

2014 ◽  
Vol 13 (1-2) ◽  
pp. 87-110 ◽  
Author(s):  
Lotsmart Fonjong
Keyword(s):  
Human Rights ◽  
West Africa ◽  
Structural Adjustment ◽  
West African ◽  
Human Rights Abuses ◽  
Structural Adjustment Programs ◽  
Liberalization Policy ◽  
The Impact ◽  
Public Demonstrations ◽  
Country Specific

Abstract In this article I argue that the worsening human rights situation of West Africa in the early 1990s was largely the creation of the structural adjustment policies (SAP) of the IMF/World Bank. The austerity measures implemented through SAP plunged the region into hardship, forcing the population to demand better living conditions through public demonstrations and protests. Attempts by the West African states to contain protesters led to further human rights abuses. The implementation of a common liberalization policy across board without taking into account the specificities of each country was counterproductive. In fact, some of the excesses recorded could have been avoided if SAPs had been country specific and human rights-based.

scholarly journals Projected Changes in the Annual Cycle of High-Intensity Precipitation Events over West Africa for the Late Twenty-First Century*

2015 ◽  
Vol 28 (16) ◽  
pp. 6475-6488 ◽  
Author(s):  
Mouhamadou Bamba Sylla ◽  
Filippo Giorgi ◽  
Jeremy S. Pal ◽  
Peter Gibba ◽  
Ibourahima Kebe ◽  
...  
Keyword(s):  
West Africa ◽  
Annual Cycle ◽  
High Intensity ◽  
Daily Precipitation ◽  
Monsoon Season ◽  
First Century ◽  
Increased Risk ◽  
Twenty First Century ◽  
Projected Changes ◽  
Precipitation Events

Abstract In this study, the response of the annual cycle of high-intensity daily precipitation events over West Africa to anthropogenic greenhouse gas for the late twenty-first century is investigated using an ensemble of high-resolution regional climate model experiments. For the present day, the RCM ensemble substantially improves the simulation of the annual cycle for various precipitation statistics compared to the driving Earth system models. The late-twenty-first-century projected changes in mean precipitation exhibit a delay of the monsoon season, consistent with previous studies. In addition, these projections indicate a prevailing decrease in frequency but increase in intensity of very wet events, particularly in the premonsoon and early mature monsoon stages, more pronounced over the Sahel and in RCP8.5 than the Gulf of Guinea and in RCP4.5. This is due to the presence of stronger moisture convergence in the boundary layer that sustains intense precipitation once convection is initiated. The premonsoon season experiences the largest changes in daily precipitation statistics, particularly toward an increased risk of drought associated with a decrease in mean precipitation and frequency of wet days and an increased risk of flood associated with very wet events. Both of these features can produce significant stresses on important sectors such as agriculture and water resources at a time of the year (e.g., the monsoon onset) where such stresses can have stronger impacts. The results thus point toward the importance of analyzing changes of precipitation characteristics as a function of the regional seasonal and subseasonal cycles of rainfall.

scholarly journals The Role of Finding Out in Type 2 Diabetes Management among West-African Immigrants Living in the UK

2021 ◽  
Vol 18 (11) ◽  
pp. 6037
Author(s):  
Folashade Alloh ◽  
Ann Hemingway ◽  
Angela Turner-Wilson
Keyword(s):  
Type 2 Diabetes ◽  
West Africa ◽  
Diabetes Management ◽  
African Immigrants ◽  
West African ◽  
Theory Approach ◽  
The Uk ◽  
West African Immigrants ◽  
The Impact

Type 2 diabetes (T2DM) prevalence is three times higher among West African Immigrants compared to the general population in the UK. The challenges of managing T2DM among this group have resulted in complications. Reports have highlighted the impact of migration on the health of the immigrant population, and this has contributed to the need to understand the influence of living in West Africa, and getting diagnosed with T2DM, in the management of their condition in the UK. Using a qualitative constructivist grounded theory approach, thirty-four West African immigrants living in the UK were recruited for this study. All participants were interviewed using Semi-structured interviews. After coding transcripts, concepts emerged including noticing symptoms, delayed diagnosis, affordability of health services, beliefs about health, feelings at diagnosis, and emotions experienced at diagnosis all contribute to finding out about diagnosis T2DM. These factors were linked to living in West Africa, among participants, and played significant roles in managing T2DM in the UK. These concepts were discussed under finding out as the overarching concept. Findings from this study highlight important aspects of T2DM diagnosis and how lived experiences, of living in West Africa and the UK, contribute to managing T2DM among West African immigrants. The findings of this study can be valuable for healthcare services supporting West African immigrants living in the UK.

scholarly journals An assessment of El Niño and La Niña impacts focused on monthly and seasonal rainfall and extreme dry/precipitation events in mountain regions of Colombia and México

2016 ◽  
Vol 42 ◽  
pp. 23-33 ◽  
Author(s):  
María Carolina Pinilla Herrera ◽  
Carlos Andrés Pinzón Correa
Keyword(s):  
El Niño ◽  
El Nino ◽  
Dry Season ◽  
La Niña ◽  
Seasonal Rainfall ◽  
Seasonal Precipitation ◽  
La Nina ◽  
Mountain Landscapes ◽  
The Impact ◽  
Precipitation Events

Abstract. The influence of El Niño and La Niña on monthly and seasonal rainfall over mountain landscapes in Colombia and México was assessed based on the Oceanic Niño Index (ONI). A statistical analysis was develop to compare the extreme dry/precipitation events between El Niño, La Niña and Neutral episodes. For both areas, it was observed that El Niño and La Niña episodes are associated with important increases or decreases in rainfall. However, Neutral episodes showed the highest occurrence of extreme precipitation/dry events. For a better understanding of the impact of El Niño and La Niña on seasonal precipitation, we did a compound and a GIS analyses to define the high/low probability of above, below or normal seasonal precipitation under El Niño, La Niña and cold/warm Neutral episodes. In San Vicente, Colombia the below-normal seasonal rainfall was identified during El Niño and Neutral episodes in the dry season JJA. In this same municipality we also found above-normal seasonal rainfall during La Niña and Neutral episodes, especially in the dry season DJF. In Tancítaro México the below-normal seasonal rainfall was identified during La Niña winters (DJF) and El Niño summers (JJA), the above-normal seasonal rainfall was found during La Niña summers (JJA) and El Niño winters (DJF).

The performance of West African Dwarf does and their kids at various stocking densities on stylo-based pasture in the subhumid zone of Nigeria

1995 ◽  
Vol 125 (2) ◽  
pp. 263-271 ◽  
Author(s):  
P. A. Iji ◽  
N. N. Umunna ◽  
J. P. Alawa ◽  
O. A. Ikwuegbu
Keyword(s):  
Weight Gain ◽  
Reproductive Performance ◽  
Body Condition Score ◽  
Stocking Density ◽  
West African ◽  
Wet Season ◽  
West African Dwarf ◽  
Weight Losses ◽  
Natural Pasture ◽  
The Impact

SUMMARYTwo studies were conducted between 1991 and 1993 to assess the impact of grazing improved v. natural pasture at different stocking densities on animal and vegetation responses. In the first grazing season, goats of the West African Dwarf (WAD) breed were grazed at four stocking densities – 1·90, 2·86, 3·86 or 4·71 TLU/ha (Tropical Livestock Unit = 250 kg liveweight). Wet-season grazing lasted for 14 weeks while assessment was continued until kids were weaned at 120 days of age. There were significant (P < 0·05) changes in the content of legume and forbs in response to variations in stocking density. Liveweight gain per head was significantly (P < 0·05) higher at low than at high stocking density. The same trend was maintained with most aspects of reproductive performance. Goats at low stocking density were of a higher (P < 0·05) body condition score at parturition and had larger litter sizes than does stocked at high stocking density. Kid birth weight and liveweight gain were significantly (P < 0·001) higher at low than at high stocking density. The overall weight loss in does during nursing was similar at the different stocking densities.In the following year, comparisons were made between three stocking densities, 2·11, 3·17 and 4·23 TLU/ha, on improved and unimproved pastures. Over 14 weeks of wet-season grazing, there was a significant (P < 0·01) decline in available dry matter except at the lowest stocking density on both pasture types. Weight gain per head decreased with increase in stocking density while the reverse was true for weight gain per unit of land. No significant differences were observed for reproductive performance between pasture types or stocking densities. Kid growth rate up to weaning declined with increase in stocking density (P < 0·001) while kid mortality rose with increase in stocking density (P < 0·01). Weight losses in nursing does were higher (P < 0·05) at low than at high stocking density.

scholarly journals Extreme Precipitation Changes in the Semiarid Region of Xinjiang, Northwest China

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Yanwei Zhang ◽  
Quansheng Ge ◽  
Minzhe Liu
Keyword(s):  
Extreme Precipitation ◽  
Daily Precipitation ◽  
Statistical Tests ◽  
Northwest China ◽  
Semiarid Region ◽  
Extreme Precipitation Events ◽  
Precipitation Records ◽  
Precipitation Changes ◽  
Climate Disasters ◽  
Precipitation Events

This study focuses on extreme precipitation changes in Xinjiang Province of Northwest China, which has experienced an increase in climate disasters in recent years. This paper investigates extreme precipitation events in Xinjiang, using 54 stations with daily precipitation records from the period 1961–2008. Different statistical tests and approaches were used to check the significance of trends of single and Xinjiang regionally aggregated precipitation series for intensity and in frequency. There were predominantly positive trends in annual maximum precipitation and a remarkable increment in the frequency of extreme precipitation over certain thresholds (from 10 to 40 mm). Although the series of frequencies exceeding thresholds had positive trends, only a minority were statistically significant. This lack of significance is because of the high variability of extreme precipitation in space and time. Thus, significant trends were evident when we assessed the extreme precipitation indicators of intensity and frequency at the regional level, both in intensity and frequency over thresholds, with a clearer signal in Xinjiang.

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