Simulations of the observed jump in the west african monsoon and its underlying dynamics using the mit regional climate model eunsoon ima,b,c and elfatih a. Understanding the variability of west african summer. Because of a lack of irrigation, most farmers in west africa are dependent on monsoon rains for sustainable crop farming ingram et al. Boreal summer variations in rainfall and winds over tropical and subtropical west africa and adjacent regions of the atlan. The west african sahel is well known for the severe droughts that ravaged this region during the 1970s and 1980s. Were this variability to increase, it might render the area close from becoming. A large amount of work has already been completed on rainfall variability of the african monsoon, through stud. This was mainly caused by interactions between the atmosphere and the ocean and above normal temperatures over the mediterranean region. Characterization of the diurnal cycle of the west african.
West african monsoon dynamics inferred from abrupt fluctuations of lake megachad simon j. Request pdf on the northward shift of the west african monsoon the regional climate model mar is used to perform a simulation of the year 1992 over west africa. Eltahird a center for environmental sensing and modeling, singaporemit alliance for research and technology, singapore. Monsoon circulations are forced and maintained by landsea thermal contrasts and by latent heat released into the atmosphere. West african monsoon definition of west african monsoon. Drakec acentre for quaternary research, department of geography, royal holloway university of london, egham, surrey, tw20 0ex, united kingdom. The african centre of meteorological applications for development acmad has issued a report describing these patterns, related flooding. West african monsoon dynamics inferred from abrupt. West african monsoon synonyms, west african monsoon pronunciation, west african monsoon translation, english dictionary definition of west african monsoon.
The central and west african region depends heavily on rainfall during the summer monsoon season, which corresponds to the northernmost migration of the intertropicalconvergencezoneitczhastenrath1991. Coupled model simulations of the west african monsoon. Monsoons are forced by the seasonal migration of the itcz, and the perturbations to this migration associated with di. Therefore it is important to investigate the major tropospheric features controlling the wasm rainfall and explore its potential to develop an objective monsoon index. Strengthening of west african monsoon during green sahara. On the northward shift of the west african monsoon. The rainfall regime of west africa is highly variable over a large range of space and time scales. The west african monsoon wam is an important climatological system which arises during the boreal summer. This chapter provides a description of the west african monsoon wam and of its variability at a wide range of space and timescales. This study analyzes decadal predictionsof the west african monsoon wam rainfallthat determines food and water security and economic development in subsaharan west africa benson and clay, 1998.
After summarizing the current understanding of its annual cycle, we analyze its variability on interannual and longer timescales including. The precipitation and atmospheric circulation patterns are shown in the adjacent figure. These findings are published in recent issues of the journal of geophysical research and the journal of climate. This plays an important role in food security and water availability. The west african monsoon consists of a lowlevel moist. A boundary forcing sensitivity analysis of the west. Simulations of the observed jump in the west african. Pdf improving the simulation of the west african monsoon. Furthermore, the onset of rains affects health organization operations, particularly for preparation and prevention of dengue. With rainfall agriculture being predominent in the region, the local population is extremely vulnerable to intraseasonal dry spells and multiyear droughts as well as to intense rainfall over small time steps. The role of lowlevel clouds in the west african monsoon system.
This mode is prominent on interannual time scales, but it does not account for all of the variability in the west african monsoon system and is not thought to be responsible for decadal trends. West african summer monsoon wasm rainfall exhibits large variability at interannual and decadal timescales, causing droughts and floods in many years. Cook 1department of geological sciences, jackson school of geosciences, the university of texas at austin, austin, texas, usa abstract the climatology and interannual variations of th e west african monsoon demise are investigated. West african monsoon, a major wind system that affects west african regions between latitudes 9 and 20 n and is characterized by winds that blow southwesterly during warmer months and northeasterly during cooler months of the year. What does the monsoon mean for the gulf of guinea and west africa. As the zone of peak solar heating moves over the sahara in june, there is a shift in the zone of peak rainfall, or intertropical convergence zone itcz, inland from the guinea coast e. Understanding the west african monsoon from the analysis of. The annual advance of the west african monsoon wam is a pivotal period for the inhabitants of the region.
September jas season proved difficult to predict because of conflicting signals and this highlights. West african monsoon synonyms, west african monsoon. Intraseasonal variability of the west african monsoon has received increased attention of late and was a significant motivation for the recent african monsoon multidisciplinary analysis amma. This paper presents the scientific challenge in west african monsoon wam simulation and discusses the west african monsoon modeling and evaluation project wamme initiative and its approaches to improve wam simulations. The data suggest that whereas the june monsoon is influenced mainly by sea surface temperatures off the coast of west africa, the august event is driven by easterly atmospheric waves generated over the african landmass. Conversely, nudging the model toward west africa suppresses the spurious enso teleconnection that is simulated over europe in the control. Climatology, interannual variations, and relationship to seasonal rainfall gang zhang 1and kerry h. Multidecadal seesaw of the impact of enso on indian and.
This work focuses on the west african monsoon wam jump and its implication for rainfed agriculture in the. The west african monsoon wam, in particular, has been shown to be sensitive to landatmosphere interactions over a range of temporal and spatial scales e. The main two components of the african monsoons are the west african monsoon, which prevails during the northern hemisphere summer june through september, and the east african monsoon with rains during spring mam and autumn ond. The west african climate is dominated by the west african monsoon wam system with a mean annual rainfall of between 150 and 2,500 mm per year. Bias reduction in decadal predictions of west african. Schematic representation of the west african monsoon. The east african monsoon is associated with the itcz moving south of the equator.
West african monsoon system is used to evaluate the ability of the coupled gcms to represent change in the system. While the seasonal progression of monsoon winds and the related migration of precipitation from the guinea. West african monsoon in stateofthescience regional. Climate of the sahel and west africa oxford research. The west african monsoon the global monsoon system. The irregularity of the rainfall during the crucial july. Projects such as the african monsoon multidisciplinary analysis programme amma. The present and future of the west african monsoon. Pdf the present assessment of the west african monsoon in the models of the coupled model intercomparison project cmip phase 5 cmip5 indicates. The west african monsoon wam has been the focus of a. West african monsoon, a major wind system that affects west african regions between latitudes 9 and 20 n and is characterized by winds that blow. Many parts of west africa and the sahel have experienced flooding since the end of july because of a very active monsoon. Investigating west african monsoon features in warm years. West african monsoon is therefore very complex because it involves.
Overview of the west african monsoon 20111 cornforth. West african monsoon article about west african monsoon. The west african monsoon onset school of earth and environment. Intraseasonal variability of the west african monsoon. The west african monsoon wam is a coupled atmosphereoceaniand system characterized by summer rainfall over the continent and winter drought. Understanding the west african monsoon variability and its. Becauseofalackofirrigation,mostfarmersinwest africa are dependent on monsoon rains for sustainable crop farming ingram et al. Intraseasonal variability of the west african monsoon and. Throughout the tropical band including southeast asia, west africa, western united states, and northern australia. The 2011 west african monsoon wam season was, overall, near normal but rainfall was patchy. West african countries it has a major influence on industrial and agricultural production, which is largely, weather dependent.
West african monsoon in stateofthescience regional climate models. Although it occurs only during a small portion of the annual cycle between may and september, the wam is a climatological. Optimal physics parameterization scheme combination of the weather research and forecasting model for seasonal precipitation simulation over ghana. Moron, west african monsoon dynamics and eastern equatorial atlantic and pacific sst anomalies 197088, journal of climate, vol. West african societies are highly vulnerable to the monsoon rainfall variability, especially in the sahel where rainfed crop production is the main source of food and income of one of the worlds most rapidly growing populations baron et al. Intraseasonal variability in the west african monsoon is documented by using daily gridded datasets of rainfall and convection, and reanalyzed.
The processes that couple the land, ocean, and atmosphere involve multiple interacting spaceand timescales. Synonyms for west african monsoon in free thesaurus. In this study, monthly mean reanalysis data from the national centers for. The vagaries of the rainfall in subsaharan africa have a profound and often dire consequence on african society and economy. Modelling the west african monsoon wam system is a challenge, as reflected, for example, in large disagreement in rainfall, surface air. Although areas just outside of this region also experience wind. Pdf the present and future of the west african monsoon. Pdf dynamics of the west african monsoon researchgate.
Following by about 46 weeks the solar zenithal position, this intertropical convergence zone itcz, moves. Wed like to understand how you use our websites in order to improve them. The diurnal cycle of the west african monsoon circulation. Request pdf the west african monsoon this chapter provides a summary of the recent advances made on the understanding and simulation of the coupled atmosphereoceanland system of the. To predict the interannual to decadal wam rainfall variability the initial and boundary conditions of.
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