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印度河上游Bagrot山谷降水稳定同位素变化及与水汽来源的关系 被引量:2
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作者 王邺凡 余武生 +3 位作者 张寅生 张腾 高海峰 MUHAMMAD Atif Wazir 《干旱区地理》 CSCD 北大核心 2019年第2期252-262,共11页
利用2015年8月—2016年7月在印度河上游流域Bagrot山谷降水稳定同位素(δ^(18)O和δD)观测结果以及当地气象资料,利用同位素示踪及统计分析方法,并结合HYSPLIT模型,对研究区降水稳定同位素变化特征、大气水线以及水汽来源进行了分析。... 利用2015年8月—2016年7月在印度河上游流域Bagrot山谷降水稳定同位素(δ^(18)O和δD)观测结果以及当地气象资料,利用同位素示踪及统计分析方法,并结合HYSPLIT模型,对研究区降水稳定同位素变化特征、大气水线以及水汽来源进行了分析。结果表明:观测期间Bagrot山谷降水稳定同位素的季节变化明显,δ^(18)O与δD秋冬季偏低,春夏季偏高,且与气温变化一致,存在显著的温度效应,而降水量效应不明显。而且发现研究区局地大气水线截距和斜率均低于全球的,反映了降水过程中云下二次蒸发作用较为强烈,因此,不同的降水形态导致该研究区局地大气水线的斜率和截距不同。当液态降水(降雨)发生时,由于在较为干旱的气候环境下,雨滴在降落的过程中受到二次蒸发相对较强,使得局地大气水线的斜率和截距偏低;而当固态降水(降雪)发生时,由于温度较低,受再循环水汽和二次蒸发的影响较小,导致局地大气水线的斜率和截距均偏高。Bagrot山谷及其周边地区,从南到北局地大气水线的斜率相差不大,而其截距总体上随着纬度升高而降低,可能与云下二次蒸发导致稳定同位素发生的不平衡分馏逐渐强烈有关。通过Bagrot山谷站点降水稳定同位素观测结果并结合HYSPLIT模型的后向追踪,研究还发现,研究区全年主要受西风环流以及局地环流的影响。但与研究区以北的临近站点(慕士塔格、和田等)相比有所不同,由于Bagrot山谷位置更靠南,其仍然偶尔受到来自南方的海洋性水汽影响。这一研究结果可能对该地区树轮稳定同位素记录的解译具有一定的指示意义。 展开更多
关键词 印度河上游 降水稳定同位素 大气水线 水汽来源
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China's meat and grain imports during 2000–2012 and beyond: A comparative perspective 被引量:4
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作者 yu wu-sheng CAO Li-juan 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2015年第6期1101-1114,共14页
This paper provides a review on China's meat trade for the 2000–2012 period and discusses its future development, with reference to China's grain trade. With marginal decreases in meat exports and slight increases ... This paper provides a review on China's meat trade for the 2000–2012 period and discusses its future development, with reference to China's grain trade. With marginal decreases in meat exports and slight increases in their imports, China's net imports of major meat products(including pork, beef, mutton and poultry but excluding meat offal) were just below 1 million tons in 2012, dwarfed by China's net imports of grains which reached 66.7 million tons in the same year. This slow growth in meat trade seems to contradict earlier expectations on increasing meat demand and imports, based upon projected shifts in consumption patterns driven by rapid per capita income growth. Several plausible explanations of this paradoxical trade pattern are offered, including mass imports of feed grains, persistent(but shrinking) gaps between Chinese and international meat prices, tariff barriers, and non-tariff measures. In the near future China may not be able to maintain such a lower profile on the world meat markets, as per capita income is projected to continue to rise and domestic production cost advantages erode due to rising labor costs. A model-based projection exercise indicates that under plausible assumptions China's meat imports may rise sharply by 2030. 展开更多
关键词 imports and beyond tariff prices capita income excluding earlier projection quota
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