Overview of the West African monsoon 2011

Although the 2011 West African monsoon (WAM) season was, overall, near normal, rainfall was patchy. The irregularity of the rainfall during the crucial July-August-September (JAS) season proved difficult to predict - highlighting the significant challenges we continue to face for this region. The vagaries of the rainfall in sub-Saharan Africa have profound and often dire effects on African society and economy. To reduce the vulnerability of African communities to variations in the strength of the WAM, the scientific community needs to improve the reliability of forecasts so as to enable forward planning, and national governments need to adopt coordinated policies in order to increase their capacity to cope with extended periods of water shortages due to drought. With the launch of the Africa Climate Exchange (Afclix), the UK and African climate communies are working with both the humanitarian sector and policy-makers to channel the latest climate science into policy. Such policies have the potential to build resilience and in-country capacity for climate compatible development in sub-Saharan Africa. The emphasis is on ‘feet on the (African) ground’ mechanisms of knowledge-sharing activities at the science-policy interface.

Examination of long-wave radiative bias in general circulation models over North Africa during May–July

Satellite data are used to quantify and examine the bias in the outgoing long-wave (LW) radiation over North Africa during May–July simulated by a range of climate models and the Met Office global numerical weather prediction (NWP) model. Simulations from an ensemble-mean of multiple climate models overestimate outgoing clear-sky long-wave radiation (LWc) by more than 20 W m−2 relative to observations from Clouds and the Earth's Radiant Energy System (CERES) for May–July 2000 over parts of the west Sahara, and by 9 W m−2 for the North Africa region (20°W–30°E, 10–40°N). Experiments with the atmosphere-only version of the High-resolution Hadley Centre Global Environment Model (HiGEM), suggest that including mineral dust radiative effects removes this bias. Furthermore, only by reducing surface temperature and emissivity by unrealistic amounts is it possible to explain the magnitude of the bias. Comparing simulations from the Met Office NWP model with satellite observations from Geostationary Earth Radiation Budget (GERB) instruments suggests that the model overestimates the LW by 20–40 W m−2 during North African summer. The bias declines over the period 2003–2008, although this is likely to relate to improvements in the model and inhomogeneity in the satellite time series. The bias in LWc coincides with high aerosol dust loading estimated from the Ozone Monitoring Instrument (OMI), including during the GERBILS field campaign (18–28 June 2007) where model overestimates in LWc greater than 20 W m−2 and OMI-estimated aerosol optical depth (AOD) greater than 0.8 are concurrent around 20°N, 0–20°W. A model-minus-GERB LW bias of around 30 W m−2 coincides with high AOD during the period 18–21 June 2007, although differences in cloud cover also impact the model–GERB differences. Copyright © Royal Meteorological Society and Crown Copyright, 2010

The statistical properties of tropical ice clouds generated by the West-African and Australian monsoons from ground-based radar-lidar observations

In the present paper we characterize the statistical properties of non-precipitating tropical ice clouds (deep ice anvils resulting from deep convection and cirrus clouds) over Niamey, Niger, West Africa, and Darwin, northern Australia, using ground-based radar–lidar observations from the Atmospheric Radiation Measurement (ARM) programme. The ice cloud properties analysed in this paper are the frequency of ice cloud occurrence, cloud fraction, the morphological properties (cloud-top height, base height, and thickness), the microphysical and radiative properties (ice water content, visible extinction, effective radius, terminal fall speed, and concentration), and the internal cloud dynamics (in-cloud vertical air velocity). The main highlight of the paper is that it characterizes for the first time the probability density functions of the tropical ice cloud properties, their vertical variability and their diurnal variability at the same time. This is particularly important over West Africa, since the ARM deployment in Niamey provides the first vertically resolved observations of non-precipitating ice clouds in this crucial area in terms of redistribution of water and energy in the troposphere. The comparison between the two sites also provides an additional observational basis for the evaluation of the parametrization of clouds in large-scale models, which should be able to reproduce both the statistical properties at each site and the differences between the two sites. The frequency of ice cloud occurrence is found to be much larger over Darwin when compared to Niamey, and with a much larger diurnal variability, which is well correlated with the diurnal cycle of deep convective activity. The diurnal cycle of the ice cloud occurrence over Niamey is also much less correlated with that of deep convective activity than over Darwin, probably owing to the fact that Niamey is further away from the deep convective sources of the region. The frequency distributions of cloud fraction are strongly bimodal and broadly similar over the two sites, with a predominance of clouds characterized either by a very small cloud fraction (less than 0.3) or a very large cloud fraction (larger than 0.9). The ice clouds over Darwin are also much thicker (by 1 km or more statistically) and are characterized by a much larger diurnal variability than ice clouds over Niamey. Ice clouds over Niamey are also characterized by smaller particle sizes and fall speeds but in much larger concentrations, thereby carrying more ice water and producing more visible extinction than the ice clouds over Darwin. It is also found that there is a much larger occurrence of downward in-cloud air motions less than 1 m s−1 over Darwin, which together with the larger fall speeds retrieved over Darwin indicates that the life cycle of ice clouds is probably shorter over Darwin than over Niamey.

Reaching the people: Isotype beyond the West

An overview of the work of the Isotype Institute in the Western Region of Nigeria in the 1950s.

'Agricultural poverty' and the expansion of artisanal mining in sub-Saharan Africa: Experiences from southwest Mali and southeast Ghana

Why do people engage in artisanal and small-scale mining (ASM) – labour-intensive mineral extraction and processing activity – across sub-Saharan Africa? This paper argues that ‘agricultural poverty’, or hardship induced by an over-dependency on farming for survival, has fuelled the recent rapid expansion of ASM operations throughout the region. The diminished viability of smallholder farming in an era of globalization and overreliance on rain-fed crop production restricted by seasonality has led hundreds of thousands of rural African families to ‘branch out’ into ASM, a move made to secure supplementary incomes. Experiences from Komana West in Southwest Mali and East Akim District in Southeast Ghana are drawn upon to illustrate how a movement into the ASM economy has impacted farm families, economically, in many rural stretches of sub-Saharan Africa.

Tropical-extratropical interactions over Southern Africa: three cases of heavy summer season rainfall

The synoptic evolution of three tropical–extratropical (TE) interactions, each responsible for extreme rainfall events over southern Africa, is discussed in detail. Along with the consideration of previously studied events, common features of these heavy rainfall producing tropical temperate troughs (TTTs) over southern Africa are discussed. It is found that 2 days prior to an event, northeasterly moisture transports across Botswana, set up by the Angola low, are diverted farther south into the semiarid region of subtropical southern Africa. The TTTs reach full maturity as a TE cloud band, rooted in the central subcontinent, which is triggered by upper-level divergence along the leading edge of an upper-tropospheric westerly wave trough. Convection and rainfall within the cloud band is supported by poleward moisture transports with subtropical air rising as it leaves the continent and joins the midlatitude westerly flow. It is shown that these systems fit within a theoretical framework describing similar TE interactions found globally. Uplift forcing for the extreme rainfall of each event is investigated. Unsurprisingly, quasigeostrophic uplift is found to dominate in the midlatitudes with convective processes strongest in the subtropics. Rainfall in the semiarid interior of South Africa appears to be a result of quasigeostrophically triggered convection. Investigation of TTT formation in the context of planetary waves shows that early development is sometimes associated with previous anticyclonic wave breaking south of the subcontinent, with full maturity of TTTs occurring as a potential vorticity trough approaches the continent from the west. Sensitivity to upstream wave perturbations and effects on anticyclonic wave breaking in the South Indian Ocean are also observed.

Isotype in Africa, 1952–58

A review of work done by the Isotype Institute in the 1940s and 1950s, associated with Africa. The chapter discusses Otto Neurath's growing interest in the last years of his life in the issue of presenting information to (West) Africans through Isotype methods. Although this interest was not realised by Otto Neurath in the form of completed work during his lifetime, Marie Neurath and the Isotype Institute did successfully carry out numerous projects in Britain's West African colonies during the 1950s, in Sierra Leone, Gold Coast (Ghana), and most extensively in the Western Region of Nigeria. Discussion of these projects illustrates the means by which Isotype work was carried out in a developing world context, the difficulties that were encountered, and the issues of effectiveness and sustainability the work raised.

Entertainment education theory and practice in HIV/AIDS communication: a South Africa / United Kingdom comparison

Within development communication, gaps remain in theory and practice: communication innovations are taking place which either do not incorporate theory or fail to challenge the assumptions of development communication and HIV/AIDS theory. This can lead to the implementation of unsuccessful interventions that lack theoretical frameworks or to uninformed practice, making it difficult to replicate. Further, research has demonstrated that Entertainment Education (EE) interventions have a measurable impact on behaviour in areas such as HIV/AIDS prevention. Given the transitions in EE practice and evidence of its impact, EE theory and practice can contribute insight into these challenges. A pilot study investigated these dilemmas within the context of the monitoring and evaluation of development communication. Framing this discussion is the concept of South-North dialogue, using comparative analysis of EE interventions to distil lessons through contrasting experiences in two diverse settings. It holds as a principle that lessons from the experience of EE in the Southern context can inform lessons for the North. Further, comparison of the case studies can generate insights for the broader development communication field. We present four case studies, informed by key informant interviews, of EE interventions in the UK and South Africa. We address how communication is defined in planning, implementation and evaluation, highlighting how it often misses the importance of 'listening'. The case studies show that HIV/AIDS communication, and development communication more broadly, has not internalised ideas of evaluation and listening in communication. Successes in the case studies can be partially attributed to responsiveness and context-specificity rather than following rigid planning templates, such as those found in some development communication literature. This indicates the importance of flexibility and responsiveness to context for both development communication and HIV/AIDS communication.

Cultural phylogeography of the Bantu Languages of sub-Saharan Africa

There is disagreement about the routes taken by populations speaking Bantu languages as they expanded to cover much of sub-Saharan Africa. Here, we build phylogenetic trees of Bantu languages and map them onto geographical space in order to assess the likely pathway of expansion and test between dispersal scenarios. The results clearly support a scenario in which groups first moved south through the rainforest from a homeland somewhere near the Nigeria–Cameroon border. Emerging on the south side of the rainforest, one branch moved south and west. Another branch moved towards the Great Lakes, eventually giving rise to the monophyletic clade of East Bantu languages that inhabit East and Southeastern Africa. These phylogenies also reveal information about more general processes involved in the diversification of human populations into distinct ethnolinguistic groups. Our study reveals that Bantu languages show a latitudinal gradient in covering greater areas with increasing distance from the equator. Analyses suggest that this pattern reflects a true ecological relationship rather than merely being an artefact of shared history. The study shows how a phylogeographic approach can address questions relating to the specific histories of certain groups, as well as general cultural evolutionary processes.

Quantifying the role of biosphere-atmosphere feedbacks in climate change: coupled model simulation for 6000 years B.P. and comparison with palaeodata for northern Eurasia and northern Africa

The LMD AGCM was iteratively coupled to the global BIOME1 model in order to explore the role of vegetation-climate interactions in response to mid-Holocene (6000 y BP) orbital forcing. The sea-surface temperature and sea-ice distribution used were present-day and CO2 concentration was pre-industrial. The land surface was initially prescribed with present-day vegetation. Initial climate “anomalies” (differences between AGCM results for 6000 y BP and control) were used to drive BIOME1; the simulated vegetation was provided to a further AGCM run, and so on. Results after five iterations were compared to the initial results in order to identify vegetation feedbacks. These were centred on regions showing strong initial responses. The orbitally induced high-latitude summer warming, and the intensification and extension of Northern Hemisphere tropical monsoons, were both amplified by vegetation feedbacks. Vegetation feedbacks were smaller than the initial orbital effects for most regions and seasons, but in West Africa the summer precipitation increase more than doubled in response to changes in vegetation. In the last iteration, global tundra area was reduced by 25% and the southern limit of the Sahara desert was shifted 2.5 °N north (to 18 °N) relative to today. These results were compared with 6000 y BP observational data recording forest-tundra boundary changes in northern Eurasia and savana-desert boundary changes in northern Africa. Although the inclusion of vegetation feedbacks improved the qualitative agreement between the model results and the data, the simulated changes were still insufficient, perhaps due to the lack of ocean-surface feedbacks.

An evaluation of the simulated water balance of Eurasia and northern Africa at 6000 yr B.P. using lake status data

Changes in the water balance of Eurasia and northern Africa in response to insolation forcing at 6000 y BP simulated by five atmospheric general circulation models have been compared with observations of changes in lake status. All of the simulations show enhancement of the Asian summer monsoon and of the high pressure cells over the Pacific and Central Asia and the Middle East, causing wetter conditions in northern India and southern China and drier conditions along the Chinese coast and west of the monsoon core. All of the models show enhancement of the African monsoon, causing wetter conditions in the zone between ca 10–20 °N. Four of the models show conditions wetter than present in southern Europe and drier than present in northern Europe. Three of the models show conditions similar to present in the mid-latitude continental interior, while the remaining models show conditions somewhat drier than present. The extent and location of each of the simulated changes varies between the models, as does the mechanism producing these changes. The lake data confirm some features of the simulations, but indicate discrepancies between observed and simulated climates. For example, the data show: (1) conditions wetter than present in central Asia, from India to northern China and Mongolia, indicating that the simulated Asian monsoon expansion is too small; (2) conditions wetter than present between ca. 10–30 °N in Africa, indicating that the simulated African monsoon expansion is too small; (3) that northern Europe was drier, but the area of significantly drier conditions was more localized (around the Baltic) than shown in the simulations; (4) that southern Europe was wetter than present, apparently consistent with the simulations, but pollen data suggest that this reflects an increase in summer rainfall whereas the models show winter precipitation, and (5) that the mid-latitude continental interior was generally wetter than present.

Erythristic leopards Panthera pardus in South Africa

Background. Leopards Panthera pardus show genetically determined colour variation. Erythristic (strawberry) morphs, where individuals are paler and black pigment in the coat is replaced by a red-brown colour, are exceptionally rare in the wild. Historically, few records exist, with only five putative records from India known. Objectives. To record the presence of erythristic leopards in our study site (Thabo Thalo Wilderness Reserve, Mpumalanga), and to collate records from across South Africa. Method. A network of camera traps was used to record individual leopards at Thabo Thalo. We also surveyed local experts, searched the popular South African press and used social media to request observations. Results. Two out of 27 individual leopards (7.1%) recorded in our study site over three years were of this colour morph. We obtained records of five other erythristic leopards in the Waterberg and Mpumalanga region, with no reports outside of this population. Conclusions. Erythristic leopards are widely dispersed across north-west South Africa, predominantly in the Lydenburg region. The presence of this rare colour morph may reflect the consequences of population fragmentation.

New Trypanosoma (Duttonella) vivax genotypes from tsetse flies in East Africa

Salivarian trypanosomes pose a substantial threat to livestock, but their full diversity is not known. To survey trypanosomes carried by tsetse in Tanzania, DNA samples from infected proboscides of Glossina pallidipes and G. swynnertoni were identified using fluorescent fragment length barcoding (FFLB), which discriminates species by size polymorphisms in multiple regions of the ribosomal RNA locus. FELLB identified the trypanosomes in 65 of 105 (61.9%) infected proboscides, revealing 9 mixed infections. Of 7 different FFLB profiles, 2 were similar but not identical to reference West African Trypanosoma vivax; 5 other profiles belonged to known species also identified in fly midguts. Phylogenetic analysis of the glycosomal glyceraldehyde phosphate dehydrogenase gene revealed that the Tanzanian T. vivax samples fell into 2 distinct groups, both outside the main chide of African and South American T. vivax. These new T. vivax genotypes were common and widespread in tsetse in Tanzania. The T. brucei-like trypanosome previously described from tsetse midguts was also found in 2 proboscides, demonstrating a salivarian transmission route. Investigation of mammalian host range and pathogenicity will reveal the importance of these new trypanosomes for the epidemiology and control of animal trypanosomiasis in East Africa.

Cathepsin L-like genes of Trypanosoma vivax from Africa and South America - characterization, relationships and diagnostic implications

We characterized sequences from genes encoding cathepsin L-like (CatL-like) cysteine proteases from African and South American isolates of Trypanosoma vivax and T. vivax-like organisms, and evaluated their suitability as genetic markers for population structure analysis and diagnosis. Phylogenetic analysis of sequences corresponding to CatL-like catalytic domains revealed substantial polymorphism, and clades of sequences (TviCatL1-9) were separated by large genetic distances. TviCatL1-4 sequences were from cattle isolates from West Africa (Nigeria and Burkina Faso) and South America (Brazil and Venezuela), which belonged to the same T. vivax genotype. T. vivax-like genotypes from East Africa showed divergent sequences, including TviCatL5-7 for isolates from Mozambique and TviCatL8-9 for an isolate from Kenya. Phylogenetic analysis of CatL-like gene data supported the relationships among trypanosome species reflected in the phylogenies based on the analysis of small subunit (SSU) of ribosomal RNA gene sequence data. The discovery of different CatL-like sequences for each genotype, defined previously by ribosomal DNA data, indicate that these sequences provide useful targets for epidemiological and population genetic studies. Regions in CatL-like sequences shared by all T. vivax genotypes but not by other trypanosomes allowed the establishment of a specific and sensitive diagnostic PCR for epidemiological studies in South America and Africa. (C) 2008 Elsevier Ltd. All rights reserved.

Phylogenetic analysis of Trypanosoma vivax supports the separation of South American/West African from East African isolates and a new T-vivax-like genotype infecting a nyala antelope from Mozambique

In this study, we addressed the phylogenetic and taxonomic relationships of Trypanosoma vivax and related trypanosomes nested in the subgenus Duttonella through combined morphological and phylogeographical analyses. We previously demonstrated that the clade T. vivax harbours a homogeneous clade comprising West African/South American isolates and the heterogeneous East African isolates. Herein we characterized a trypanosome isolated from a nyala antelope (Tragelaphus angasi) wild-caught in Mozambique (East Africa) and diagnosed as T. vivax-like based on biological, morphological and molecular data. Phylogenetic relationships, phylogeographical patterns and estimates of genetic divergence were based on SSU and ITS rDNA sequences of T. vivax from Brazil and Venezuela (South America), Nigeria (West Africa), and from T. vivax-like trypanosomes from Mozambique, Kenya and Tanzania (East Africa). Despite being well-supported within the T. vivax clade, the nyala trypanosome was highly divergent from all other T. vivax and T. vivax-like trypanosomes, even those from East Africa. Considering its host origin, morphological features, behaviour in experimentally infected goats, phylogenetic placement, and genetic divergence this isolate represents a new genotype of trypanosome closely phylogenetically related to T. vivax. This study corroborated the high complexity and the existence of distinct genotypes yet undescribed within the subgenus Duttonella.