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81.
全球变暖背景下区域气候变化响应已引起学术界的高度关注,将气候变化与干旱趋势相结合进行研究具有理论意义。利用衡阳盆地1981—2013年的逐日气温和降水量,综合分析衡阳盆地的气候变化特征与干旱发展趋势。结果表明:衡阳盆地的气候呈暖干趋势发展,年平均气温增加0.034 1℃,其中春季升温贡献最大,春季气温年增加0.054 4℃;年降水量约减少0.808 0 mm,呈缓慢减少趋势,以秋季降水的减幅最大,年减少3.335 1 mm;利用综合气象干旱指数(CDI)法计算出干旱频率年增加0.379 9%,其中秋季干旱频率增加最大,年增加0.910 4%,不同等级干旱类型中,以特旱频率增加率最大,年增加0.231 6%。 相似文献
82.
利用河北省棉区1961—2010年15个站点逐日气象资料,分析了河北省不同棉区气候周期振荡及突变点,结果表明:不同棉区棉花全生育期气温、降水、日照均存在多个时间尺度的周期变化特征,交替现象明显;全生育期平均气温年代际以及年际主要周期:冀南、冀中棉区为20~22 a、9~10 a、5~7 a,冀东棉区为22~24 a、11~14 a,全生育期平均气温升高明显,在1996年发生了突变,转入气温相对较高期。全生育期降水主要周期:冀南棉区为14~15 a,冀中、冀东棉区为22~24 a、8~10 a。全生育期日照存在9~10 a振荡周期,且1986年前后发生突变,转入相对偏少期。 相似文献
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84.
Takashi Kitagawa Shingo Kimura Hideaki Nakata Harumi Yamada 《Fisheries Oceanography》2004,13(3):161-180
Twenty‐four archival tags were recovered from Pacific bluefin tuna previously released off Tsushima Island in the East China Sea. By analysis of the time‐series data of the pressure and the ambient and internal temperature from the 24 tags, we examined the relationship between the tuna's pattern of diving and the thermocline depth. In the East China Sea, diving and feeding events occurred throughout almost the entire day in both winter and summer, suggesting that the purpose of diving is for feeding. In summer, the feeding frequency was greater than that in winter, which corresponds to the fact that growth is more rapid in summer than in winter. During summer in the Kuroshio–Oyashio transition region, on the other hand, feeding events were much more frequent than those in the East China Sea, in spite of a lower diving frequency. The mean horizontal distance traveled was also significantly higher and it seems that in this area they may move horizontally to feed on prey accumulated at the surface. We conclude that, in addition to the ambient temperature structure, the vertical and horizontal distribution of prey species plays an important role in the feeding behavior of Pacific bluefin tuna. One bluefin tuna migrated to the Oyashio frontal area, where both the horizontal and the vertical thermal gradients are much steeper. The fish spent most of the time on the warmer side of the front and often traveled horizontally to the colder side during the day, perhaps to feed. This implies that there is a thermal barrier effect, in this case from the Oyashio front, on their behavior. The frequency of feeding events was low, although all the monitored fish dived every dawn and dusk, irrespective of the seasons or location. It is possible that these twice‐daily diving patterns occurred in response to the change in ambient light at sunrise and sunset. 相似文献
85.
Maltais E, Daigle G, Colbeck G, Dodson JJ. Spawning dynamics of American shad (Alosa sapidissima) in the St. Lawrence River, Canada–USA.Ecology of Freshwater Fish 2010: 19: 586–594. © 2010 John Wiley & Sons A/S Abstract – The most northerly population of American shad (Alosa sapidissima), located in the St. Lawrence River, is considered vulnerable because of low population abundance and limited spawning habitat located at the upstream extent of the population’s anadromous migration. Here, we aimed to establish the temporal and spatial extent of spawning based on a novel hatch‐date analysis of juveniles. Spawning activity lasted from early May to early July. We found that juveniles captured downstream during the summer hatched later in the year than those captured further upstream. As a result, younger juveniles were distributed somewhat further downstream. In addition, we found significant multimodality in hatch‐date distributions at midstream and downstream sampling stations. Together, these results provide evidence that the 2‐month spawning period involved numerous spawning events that progressed in a downstream direction as the season advanced, rather than being restricted to upstream sites over the spawning season. 相似文献
86.
运用文献资料法、对比研究法和归纳演绎法对我国女子持拍隔网对抗类项目的发展状况进行研究,总结该项群成为优势项目的成功经验,为潜优势项目发展提供借鉴。研究表明体制发展优势、奥运发展战略、完善的后备梯队建设和高水平联赛体系以及技战术创新等是乒乓球、羽毛球运动成为优势项目的主要支持。为实现潜优势项目向优势项目的过渡,应继续优化管理模式、提升教练员执教能力、完善青少年后备人才体系和竞赛机制。 相似文献
87.
Chen Fei Wang Jianmin Sun Baogang Chen Xiaoming Yang Zixiang Duan Zhaoyao 《中国林业科技(英文版)》2012,(3):47-48
A distribution map of Pinus yunnanensis was made according to the data on geographical distribution of P.yunnanensis by means of applying geographic information systems software ArcGIS, and the climatic parameters of the distribution areas for P.yunnanensis were determined by the climate forecast model Climate China.The relationship between the geographical distribution of P.yunnanensis and the climate was studied by adopting the indexes of Kira including the warmth index(WI),coldness index(CI) and aridity index (K),Xu’s humidity index(HI),Holdridge’s life temperature(BT),potential evapotranspiration (PET),potential evapotranspiration ratio(PER) and the single factors as the mean annual temperature, the mean temperature in January,the mean temperature in July,the mean annual precipitation, the>5℃accumulated temperature,the>18℃accumulated temperature,the maximum temperature, the minimum temperature,the temperature variation, the ratio of temperature and precipitation of the year, etc.And the Kira’s water-temperature indexes on distributional upper limit,low limit and north limit were discussed.The major climatic factors effecting the distribution of P.yunnanensis were screened out by statistical analysis software SPSS and the results showed the impact factors are in the order of temperature>humidity>the temperature difference between mean warmest month temperature and mean coldest month temperature. 相似文献
88.
For spatial crop and agro-systems modelling, there is often a discrepancy between the scale of measured driving data and the target resolution. Spatial data aggregation is often necessary, which can introduce additional uncertainty into the simulation results. Previous studies have shown that climate data aggregation has little effect on simulation of phenological stages, but effects on net primary production (NPP) might still be expected through changing the length of the growing season and the period of grain filling. This study investigates the impact of spatial climate data aggregation on NPP simulation results, applying eleven different models for the same study region (∼34,000 km2), situated in Western Germany. To isolate effects of climate, soil data and management were assumed to be constant over the entire study area and over the entire study period of 29 years. Two crops, winter wheat and silage maize, were tested as monocultures. Compared to the impact of climate data aggregation on yield, the effect on NPP is in a similar range, but is slightly lower, with only small impacts on averages over the entire simulation period and study region. Maximum differences between the five scales in the range of 1–100 km grid cells show changes of 0.4–7.8% and 0.0–4.8% for wheat and maize, respectively, whereas the simulated potential NPP averages of the models show a wide range (1.9–4.2 g C m−2 d−1 and 2.7–6.1 g C m−2 d−1 for wheat and maize, respectively). The impact of the spatial aggregation was also tested for shorter time periods, to see if impacts over shorter periods attenuate over longer periods. The results show larger impacts for single years (up to 9.4% for wheat and up to 13.6% for maize). An analysis of extreme weather conditions shows an aggregation effect in vulnerability up to 12.8% and 15.5% between the different resolutions for wheat and maize, respectively. Simulations of NPP averages over larger areas (e.g. regional scale) and longer time periods (several years) are relatively insensitive to climate data aggregation. However, the scale of climate data is more relevant for impacts on annual averages of NPP or if the period is strongly affected or dominated by drought stress. There should be an awareness of the greater uncertainty for the NPP values in these situations if data are not available at high resolution. On the other hand, the results suggest that there is no need to simulate at high resolution for long term regional NPP averages based on the simplified assumptions (soil and management constant in time and space) used in this study. 相似文献
89.
Little information exists concerning how crops will respond to the predicted increased night temperatures. The objective of this work was to determine if respiration and growth of sorghum [Sorghum bicolor (L.) Moench], a C, plant, and sunflower (Helianthus annuus L.), a C3 plant, are affected when the night temperature is increased by 5°C compared to the long-term (19 year) average night temperature in June in Kansas. Sorghum and sunflower were grown in two walk-in growth chambers with either the ambient night temperature (21C) or a high night temperature (26C). Day temperature was the same for all plants (27C). Both sunflower and sorghum had higher respiration rates under the elevated night temperature than under the ambient temperature. The average respiration rate of sunflower grown under elevated night temperature increased by 19% (0.89 vs. 0.75 μmol m?2 s?1) and that of sorghum by 44 % (0.52 vs. 0.36μmol m?2s?1). After 74 days, sunflower plants grown under the ambient night temperature were 30.2 cm taller than sunflower plants grown under the elevated night temperature; sorghum plants under the ambient temperature were 24.8 cm taller. Sunflower plants grown under the elevated night temperature formed flowers one week earlier than those grown under the ambient temperature. Sorghum formed no flowers by 74 days. Results suggest that, if climate change does increase night temperature, respiration will be increased more in C4, than C3 plants. 相似文献
90.