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951.
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一种以能量平衡为基础的干旱指数 总被引:5,自引:0,他引:5
本文以能量平衡公式为基础,根据实际蒸发与潜在蒸发的关系依赖于土壤水分含量的事实,导出一种表达干湿状况的指标——土壤水分干旱指数。 相似文献
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棉铃虫Helicoverpa armigera 属鳞翅目夜蛾科,是一种世界性的重大害虫,在世界各地均有分布。因其具有远距离迁飞,繁殖力强等特点,条件适宜时常大面积暴发成灾,给农业生产带来较大损失。摸清棉铃虫生活习性、种群变化规律是棉铃虫防治的前提条件。由于棉铃虫是变温昆虫,气候条件对其生长发育、成灾机制等产生极大影响。因此,本文系统综述了气候变暖对棉铃虫影响的研究进展,包括棉铃虫生长发育、体色变化、繁殖、滞育、飞行、越冬、与作物的互作关系等方面,并对未来研究重点进行了展望。以期对棉铃虫的综合治理提供理论依据。 相似文献
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Impacts of Climatic Factors on Runoff Coefficients in Source Regions of the Huanghe River 总被引:4,自引:0,他引:4
CHEN Liqun LIU Changming LI Yanping WANG Guoqiang 《中国地理科学(英文版)》2007,17(1):047-055
Runoff coefficients of the source regions of the Huanghe River in 1956–2000 were analyzed in this paper. In the 1990s runoff of Tangnaihai Hydrologic Station of the Huanghe River experienced a serious decrease, which had at- tracted considerable attention. Climate changes have important impact on the water resources availability. From the view of water cycling, runoff coefficients are important indexes of water resources in a particular catchment. Kalinin baseflow separation technique was improved based on the characteristics of precipitation and streamflow. After the separation of runoff coefficient (R/P), baseflow coefficient (Br/P) and direct runoff coefficient (Dr/P) were estimated. Statistic analyses were applied to assessing the impact of precipitation and temperature on runoff coefficients (including Dr/P, Br/P and R/P). The results show that in the source regions of the Huanghe River, mean annual baseflow coefficient was higher than mean annual direct runoff coefficient. Annual runoff coefficients were in direct proportion to annual pre- cipitation and in inverse proportion to annual mean temperature. The decrease of runoff coefficients in the 1990s was closely related to the decrease in precipitation and increase in temperature in the same period. Over different sub-basins of the source regions of the Huanghe River, runoff coefficients responded differently to precipitation and temperature. In the area above Jimai Hydrologic Station where annual mean temperature is –3.9oC, temperature is the main factor in- fluencing the runoff coefficients. Runoff coefficients were in inverse relation to temperature, and precipitation had nearly no impact on runoff coefficients. In subbasin between Jimai and Maqu Hydrologic Station Dr/P was mainly affected by precipitation while R/P and Br/P were both significantly influenced by precipitation and temperature. In the area be-tween Maqu and Tangnaihai hydrologic stations all the three runoff coefficients increased with the rising of annual precipitation, while direct runoff coefficient was inversely proportional to temperature. In the source regions of the Huanghe River with the increase of average annual temperature, the impacts of temperature on runoff coefficients be-come insignificant. 相似文献