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141.
142.
干旱地区灌溉生产函数与经济用水灌溉定额的确定方法探讨 总被引:2,自引:0,他引:2
本文利用最优化计算方法,分析了干旱地区作物产量与灌溉定额之间的关系,论证了灌溉生产函数的求解与经济用水灌溉定额的确定方法,为灌区计划用水提供科学根据。 相似文献
143.
西太平洋副热带高压异常进退的对比分析 总被引:4,自引:4,他引:0
对1980年7月29日—8月16日西太平洋副高位置持续偏南和1983年7月16日—8月12日西太平洋副高位置持续偏北的两次季节内副高中期进退过程的环流特征和加热差异作了对比分析,讨论了东亚季风与对流活动、副高进退之间的关系. 相似文献
144.
利用梯度分析技术对12种锦鸡儿属植物抗旱性的定量研究 总被引:4,自引:0,他引:4
利用梯度分析技术对锦鸡儿属12种植物8个生理指标进行分析, 计算出了植物的抗旱梯度值; 建立了抗旱梯度轴; 排出了植物的抗旱性顺序; 并指出了影响植物抗旱能力的主导因子。植物的抗旱梯度值与束/自比之间呈线性相关, 相关系数为0.9204, 相关方程为y=1.5696+0.0911x。 相似文献
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146.
Ognjen Bonacci 《水文研究》1993,7(3):249-262
The problem of drought identification is considered from a primarily hydrological viewpoint. The problems related to the definition, identification and prediction of drought have not yet been solved. Although rainfall data are analysed as the main indicator and characteristic of drought, other characteristics resulting from a rainfall deficit are also important. A time unit of one month was selected as the most suitable for analysis. Special attention was paid to the selection of truncation levels with respect to their influence on the results of drought identification. Three methods for drought identification were applied to a series of monthly rainfall data in Osijek from January 1882 to December 1990: (1) run analysis; (2) a discrete Markov process; and (3) the percentile method. Although the results of these three methods are encouraging, different methods yielded similar results. Some drawbacks of the application of distribution curves are discussed. Drought events should be identified using a number of different procedures. 相似文献
147.
We provide a position paper, using a brief literature review and some new modelling results for a subset of succulent plant species, which explores why Namaqualand plant diversity might be particularly vulnerable to anthropogenic climate change despite presumed species resilience under arid conditions, and therefore a globally important test-bed for adaptive conservation strategies. The Pleistocene climate-related evolutionary history of this region in particular may predispose Namaqualand (and Succulent Karoo) plant endemics to projected climate change impacts. Key Succulent Karoo plant lineages originated during cool Pleistocene times, and projected air temperatures under anthropogenic climate change are likely to exceed these significantly. Projected rainfall patterns are less certain, and projections of the future prevalence of coastal fog are lacking, but if either of these water inputs is reduced in concert with rising temperatures, this seems certain to threaten the persistence of, at least, narrow-endemic plant species. Simple modelling approaches show strong reduction in spatial extent of bioclimates typical of Namaqualand within the next five decades and that both generalist species with large geographic ranges, and narrow-range endemics may be susceptible to climate change induced loss of potential range. Persistence of endemics in micro-habitats that are buffered from extreme climate conditions cannot be discounted, though no attempts have been made to address this shortcoming of broader scale bioclimatic modelling. The few experimental data available on elevated temperature and drought tolerance suggest susceptibility of leaf succulent species, but high drought tolerance of non-succulent shrubs. Both species-level monitoring and further experimental work is essential to test and refine projections of climate change impacts on species persistence, and the implications for conservation. 相似文献
148.
植被状况指数的改进及在西北干旱监测中的应用 总被引:8,自引:0,他引:8
干旱是全球分布最广、发生频率最高、持续时间最长、影响范围最大、造成的经济损失最为严重的一种自然灾害,干旱也是所有自然灾害中影响因子最为复杂、人类了解最少、监测最为困难的一种自然灾害,干旱监测是世界性的难题。干旱可以发生在任何气候带上,但干旱、半干旱地区是全球干旱灾害发生最频繁的地区。干旱发生特征和规律因地区的不同会有很大的差异,不同地区对干旱监测方法不同。目前,世界各国干旱监测主要利用基于气象、水文、农业和卫星遥感等观测资料建立的各种干旱指数开展,已经有150多种干旱指数。植被状况指数VCI是应用最为广泛的一种卫星监测干旱的指数,研究和业务应用结果表明,VCI对全球各地的干旱均有较好的反映,已经应用在美国国家大气海洋局(NOAA)日常干旱监测业务中,中国国家卫星气象中心干旱卫星遥感监测服务产品也是以VCI为基础。
我国干旱半干旱地区主要分布在新疆、甘肃、青海、陕西、宁夏以及内蒙古自治区的中西部,这里降水少且不稳定,降水变率大,是中国干旱发生频率最高的地区。干旱严重制约着当地经济发展和人类生活质量的提高,使本身非常脆弱的生态环境趋于恶化。为了了解条件植被指数VCI对西北地区不同气候区干旱的监测能力,以上述6省(区)为研究区,利用1982—2003年22年NDVI数据,计算了研究区域22年来逐月的VCI,对比分析了不同气候区VCI与降水距平的关系。结果表明,VCI在空间和时间上较好地反映了西北大部分气候干旱发生、发展和空间分布,是干旱监测的较好指标,但在干旱和极端干旱地区,VCI经常出现异常偏高现象,不能反映干旱气候区常年干旱的基本特点。通过对西北不同生态系统之间NDVI特点和各生态系统间NDVI年变化及其年际变化规律的研究,设计了VCI改进方案,提出了改进的条件植被指数RVCI。通过对22年来逐月RVCI与VCI的对比,RVCI客观地反映了干旱气候区常年干旱特点,较VCI有显著改进。
相似文献
149.
150.
A new assessment of climate change impacts on food production shortfalls and water availability in Russia 总被引:2,自引:0,他引:2
Joseph Alcamo Nikolai Dronin Marcel Endejan Genady Golubev Andrei Kirilenko 《Global Environmental Change》2007,17(3-4):429-444
While previous studies have focused on impacts of average climate change on Russian agriculture and water resources, this study takes into account the impact of changing frequency and spatial heterogeneity of extreme climate events, and the reliance of most of Russia on a few food producing regions. We analyze impacts of the IPCC A2 and B2 climate scenarios with the use of the Global Assessment of Security (GLASS) model (containing the Global Agro-Ecological Zones (GAEZ) crop production model and the Water-Global Assessment and Prognosis (WaterGAP 2) water resources model). As in previous studies we find that decreased crop production in some Russian regions can be compensated by increased production in others resulting in relatively small average changes. However, a different perspective on future risk to agriculture is gained by taking into account a change in frequency of extreme climate events. Under climate normal conditions it is estimated that “food production shortfalls” (a year in which potential production of the most important crops in a region is below 50% of its average climate normal production, taking into account production in food-exporting regions) occur roughly 1–3 years in each decade. This frequency will double in many of the main crop growing areas in the 2020s, and triple in the 2070s. The effects of these shortfalls are likely to propagate throughout Russia because of the higher likelihood of shortfalls occurring in many crop export regions in the same year, and because of the dependence of most Russian regions on food imports from a relatively few main crop growing regions. We estimate that approximately 50 million people currently live in regions that experience one or more shortfalls each decade. This number may grow to 82–139 million in the 2070s. The assessment of climate impacts on water resources indicates an increase in average water availability in Russia, but also a significantly increased frequency of high runoff events in much of central Russia, and more frequent low runoff events in the already dry crop growing regions in the South. These results suggest that the increasing frequency of extreme climate events will pose an increasing threat to the security of Russia's food system and water resources. 相似文献