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Recent drought and precipitation tendencies in Ethiopia 总被引：3，自引：0，他引：3
Ellen Viste Diriba Korecha Asgeir Sorteberg 《Theoretical and Applied Climatology》2013,112(3-4):535-551
In 2011, drought in the Horn of Africa again made news headlines. This study aims to quantify the meteorological component of this and other drought episodes in Ethiopia since 1971. A monthly precipitation data set for 14 homogeneous rainfall zones was constructed based on 174 gauges, and the standardized precipitation index was calculated on seasonal, annual, and biannual time scales. The results point to 2009 as a year of exceptionally widespread drought. All zones experienced drought at the annual scale, although in most zones, previous droughts were more extreme. Nationally, 2009 was the second driest year, surpassed only by the historic year 1984. Linear regression analysis indicates a precipitation decline in southern Ethiopia, during both February–May and June–September. In central and northern Ethiopia, the analysis did not provide evidence of similar tendencies. However, spring droughts have occurred more frequently in all parts of Ethiopia during the last 10–15 years. 相似文献
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A climate trend analysis of Ethiopia: examining subseasonal climate impacts on crops and pasture conditions 总被引：3，自引：0，他引：3
Molly E. Brown Chris Funk Diego Pedreros Diriba Korecha Melesse Lemma James Rowland Emily Williams James Verdin 《Climatic change》2017,142(1-2):169-182
Ethiopia experiences significant climate-induced drought and stress on crop and livestock productivity, contributing to widespread food insecurity. Here, we present subseasonal crop water stress analyses that indicate degrading, growing conditions along Ethiopia’s eastern highlands, including productive and populated highland regions. These seasonally shifting areas of increasing water stress stretch from the north to south across eastern Ethiopia, intersecting regions of acute food insecurity and/or high population. Crop model simulations indicate that between 1982 and 2014, parts of eastern Amhara and eastern Oromia experienced increasing water deficits during the critical sowing, flowering, and ripening periods of crop growth. These trends occurred while population in these regions increased by 143% between 2000 and 2015. These areas of enhanced crop water stress in south-central Ethiopia coincide with regions of high population growth and ongoing crop extensification. Conversely, large regions of relatively unpopulated western Ethiopia are becoming wetter. These areas may therefore be good targets for agricultural development. 相似文献
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Random noise attenuation, preserving the events and weak features by improving signal‐to‐noise ratio and resolution of seismic data are the most important issues in geophysics. To achieve this objective, we proposed a novel seismic random noise attenuation method by building a compound algorithm. The proposed method combines sparsity prior regularization based on shearlet transform and anisotropic variational regularization. The anisotropic variational regularization which is based on the linear combination of weighted anisotropic total variation and anisotropic second‐order total variation attenuates noises while preserving the events of seismic data and it effectively avoids the fine‐scale artefacts due to shearlets from the restored seismic data. The proposed method is formulated as a convex optimization problem and the split Bregman iteration is applied to solve the optimization problem. To verify the effectiveness of the proposed method, we test it on several synthetic seismic datasets and real datasets. Compared with three methods (the linear combination of weighted anisotropic total variation and anisotropic second‐order total variation, shearlets and shearlet‐based weighted anisotropic total variation), the numerical experiments indicate that the proposed method attenuates random noises while alleviating artefact and preserving events and features of seismic data. The obtained result also confirms that the proposed method improves the signal‐to‐noise ratio. 相似文献
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