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Recent summer precipitation trends in the Greater Horn of Africa and the emerging role of Indian Ocean sea surface temperature 总被引：1，自引：0，他引：1
A. Park Williams Chris Funk Joel Michaelsen Sara A. Rauscher Iain Robertson Tommy H. G. Wils Marcin Koprowski Zewdu Eshetu Neil J. Loader 《Climate Dynamics》2012,39(9-10):2307-2328
We utilize a variety of climate datasets to examine impacts of two mechanisms on precipitation in the Greater Horn of Africa (GHA) during northern-hemisphere summer. First, surface-pressure gradients draw moist air toward the GHA from the tropical Atlantic Ocean and Congo Basin. Variability of the strength of these gradients strongly influences GHA precipitation totals and accounts for important phenomena such as the 1960s–1980s rainfall decline and devastating 1984 drought. Following the 1980s, precipitation variability became increasingly influenced by the southern tropical Indian Ocean (STIO) region. Within this region, increases in sea-surface temperature, evaporation, and precipitation are linked with increased exports of dry mid-tropospheric air from the STIO region toward the GHA. Convergence of dry air above the GHA reduces local convection and precipitation. It also produces a clockwise circulation response near the ground that reduces moisture transports from the Congo Basin. Because precipitation originating in the Congo Basin has a unique isotopic signature, records of moisture transports from the Congo Basin may be preserved in the isotopic composition of annual tree rings in the Ethiopian Highlands. A negative trend in tree-ring oxygen-18 during the past half century suggests a decline in the proportion of precipitation originating from the Congo Basin. This trend may not be part of a natural cycle that will soon rebound because climate models characterize Indian Ocean warming as a principal signature of greenhouse-gas induced climate change. We therefore expect surface warming in the STIO region to continue to negatively impact GHA precipitation during northern-hemisphere summer. 相似文献
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Girmachew Adugna Zewdu 《GeoJournal》2018,83(5):1019-1034
Although Ethiopia has seen a reduction in refugee flows over the past decade, documented and undocumented labour migration has significantly increased. International migration has changed from that born out of conflict to irregular migration mainly driven by economic reasons. The source of migrants has expanded from urban centres to include rural areas, making them an important source of low-skilled labour for the international labour market. Based on a qualitative study, this paper explores the process and pattern of Ethiopian migration to South Africa, an emerging destination in the global South. This migration corridor is increasingly characterised by its irregularity. The paper also reflects how migration patterns shape the pattern of remittance flow, along with the way in which migrants and their networks substitute the function of financial institutions engaged in the remittance industry. It also highlights the features of remittances utilisation in emerging rural migrant community in Southern Ethiopia. 相似文献
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这篇文章旨在构建一个期权定价模型以减少与埃塞俄比亚咖啡价格波动相关的风险。我们使用从埃塞俄比亚商品交易所(ECX)获得的2011年5月31日至2018年3月30日期间记录的埃塞俄比亚每日(WSDA3)咖啡价格来分析其咖啡价格的波动。本文使用跳跃扩散模型对咖啡价格进行建模和期权定价,应用最大似然法估计模型参数,使用均方根误差(RMSE)来对模型进行验证。结果表明Merton和双指数跳跃扩散模型的RMSE值分别为0.1093和0.0783,模型模拟结果与实际数据非常吻合,说明采用蒙特卡罗技术得到的WSDA3价格来对期权定价时,双指数跳跃扩散模型比Merton模型更为有效。 相似文献
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