中国西北地区6月降水量最近30年明显递增   总被引：10，自引：0，他引：10       下载免费PDF全文

王宝灵 《气象》1997,23(6):37-39

通过分析１９６１－１９９０年中国西北地区５省（区）８９个测站月降水量资料，指出６月降水量最近３０的递增明显。  相似文献   

Sea level change: a philosophical approach     

R. Leinfelder  H. Seyfried 《International Journal of Earth Sciences》1993,82(2):159-172

The present Cenozoic era is an icehouse episode characterized by a low sea level. Since the beginning of the industrial revolution, the human race has been emitting greenhouse gases, increasing the global atmospheric temperature, and causing a rise in sea level. If emissions continue to increase at the present rate, average global temperatures may rise by 1.5°C by the year 2050, accompanied by a rise of about 30 cm in sea level. However, the prediction of future climatic conditions and sea level is hampered by the difficulty in modelling the interactions between the lithosphere, kryosphere, biosphere and atmosphere; in addition, the buffering capacity of our planet is still poorly understood. As scientists cannot offer unambiguous answers to simple questions, sorcerer's apprentices fill in the gaps, presenting plans to save planet without inconveniencing us.The geological record can help us to learn about the regulation mechanisms of our planet, many of which are connected with or expressed as sea level changes. Global changes in sea level are either tectono-eustatic or glacioeustatic. Plate tectonic processes strongly control sea levels and climate in the long term. There is a strong feed-back mechanism between sea level and climate; both can influence and determine each other. Although high sea levels are a powerful climatic buffer, falling sea levels accelerate climatic accentuation, the growth of the polar ice caps and will hence amplify the drop in sea level. Important sources of fossil greenhouse gases are botanic CO₂ production, CO₂ released by volcanic activity, and water vapour. The latter is particularly important when the surface area of the sea increases during a rise in sea level (maritime greenhouse effect). A volcanogenic greenhouse effect (release of volcanogenic CO₂) is possibly not equally important, as intense volcanic activity may take place both during icehouse episodes as well as during greenhouse episodes. The hydrosphere, land vegetation and carbonate platforms are major CO₂ buffers which may both take up and release CO₂. CO₂ can be released from the ocean due to changes in the pCO₂ caused by growth of coral reefs and by uptake of CO₂-rich freshwater from karst provinces. Efficient sinks of CO₂ are the weathering products of silicate rocks; long-term sinks are organic deposits caused by regional anoxic events which preferrably develop during sea level rises and highstands; and coal-bearing strata. Deposition of limestone also removes CO₂ from the atmospheric-hydrospheric cycle at a long term. Biotic crises are often related to either sea-level lows or sea-level highs. Long-term sea-level lows, characteristic of glacial periods, indicate cooling as major cause of extinction. During verly long-lasting greenhouse episodes the sea level is very high, climate and circulation systems are stable and biotic crises often develop as a consequence of oxygen depletion. On land, niche-splitting, complex food web structures and general overspecialization of biota will occur. Whether the crisis is caused by a single anoxic event (e.g. in the Late Devonian) or a disturbance by an asteroid impact (e.g. the Cretaceous/Tertiary boundary), it will only trigger total collapse of an ecosystem if a large part of it was already in decline. The regulatory mechanisms and buffers are thermodynamically extremely efficient if they are given sufficient time in which to deploy their power. However, after major catastrophes the re-establishment of successful ecosystems will take millions of years. The present rate of sea level and associated temperature rise is much too fast to be compensated and buffered by the network of natural controls. It is likely that the transitional time towards a new steady state will be an extremely variable and chaotic episode of unpredictable duration. Correspondence to: H. Seyfried  相似文献   

2005年9月18日山东突发区域性暴雨过程分析   总被引：7，自引：0，他引：7  

孙兴池  王建国  薛德强  王业宏 《中国海洋大学学报(自然科学版)》2006,36(4):595-600

利用常规资料及MM5模式模拟结果,对2005年9月18日山东突发区域性暴雨过程进行了分析。结果表明:近地面层浅薄冷空气的侵入、相当位温密集区附近对流稳定度θep的减小导致垂直涡度的显著增长及低层对流稳定条件下的倾斜上升运动可能是本次暴雨过程发生的机制。  相似文献   

微齿喜马拉雅低额溞生长及种群增长的研究     

施心路  于丽杰  张大维  史新柏 《海洋与湖沼》1997,28(3):262-270

于1990年6月在哈尔滨市东北林业大学实验林场一水池中采到微齿喜马拉雅低额，根据实验结果应用生物统计学方法对它的生长和种群增长进行研究。结果表明，在不同温度条件下性成熟时间与水温的关系为，雌性（10-30℃）：h=8072t－1.313（r=0．985P＜0.01）；雄性（5－25℃）：h=1074t-0.855（r=0.9844，P＜0.01）。在20±1℃条件下，其体长增长模型为：lt=3.334-27345e－0.1117t。龄期（X）与年龄（t，d）的关系为：雌体：t=0·07l69X2＋1.3808X－l·7361；雄体：t=0.8425X2＋2.534x－l.8600。内禀增长率（rm）为0．4076。种群增长呈“logistic”型，其方程式为：  相似文献   

35GHz毫米波对生物离体皮肤组织表面辐照温升的研究   总被引：1，自引：0，他引：1  

谢国秋  程和平 《中国海洋大学学报(自然科学版)》2006,36(3):513-516

研究不同的功率密度35GHz毫米波对离体皮肤组织的辐照温升的问题。低功率辐照10min皮肤温度上升13.6℃;高功率辐照10s内,皮肤表面温升达10℃左右,皮肤的失水量较大。温升曲线和热传导方程计算结果做了对比,结果表明,低功率辐照下2mm厚样品的温升曲线和理论曲线较吻合,很显然,对于理论计算而言,35GHz毫米波辐照下2mm厚度以上的离体皮肤组织可以视为是半无限大的组织。聚焦的高功率毫米波的辐照温升与理论计算结果相比相差较大,文中对导致这种差异的可能原因进行了分析。  相似文献   

A DIAGNOSTIC EXPERIMENTAL STUDY OF EFFECTS OF CO₂ ENRICHMENT ON COTTON GROWTH, DEVELOPMENT AND YIELD          下载免费PDF全文

Wang Chunyi  Bai Yueming  Wen Min 《Acta Meteorologica Sinica》1995,9(4):501-508

A series of experiments were conducted about the effects of different CO₂ concentrations and ventilating time on cotton using OPT-1 open top chambers.The results show that.for all the ventilating treatments,the development stages of cotton were advanced,plant height increased,the biomass of root and stalk increased when CO₂ concentration increased:the number of bolls formed in summer was more than 85% of the total for the treatment of 700 ppm CO₂ concentration;single boll weight,the number of bolls per plant,ginned and unginned cotton weights,and stalk weight increased obviously when CO₂ concentration increased,but the influences of CO₂ enrichment on the ratio of ginned weight to the total weight of ginned and unginned cotton,fibre length and ginned weight of 100-seed were small.  相似文献   

气爆对煤体渗透性影响的实验研究     

曾范永  李成全  孙可明  宋维源  李赞 《煤田地质与勘探》2012,40(2):35-38

我国煤层的渗透率普遍偏低,采用常规增产改造和降压开发技术难以奏效。因此,提出了一种全新的卸压增透技术-气爆。阐述了气爆的实验原理、实验过程及气爆前后渗透率的对比。通过对40组气爆实验数据的分析研究可知:在气爆压力相近的情况下,当煤的硬度系数f为0.5~0.9,且渗透率k为0.001~0.005 D时,气爆效果更明显,部分煤体的渗透率甚至增加了10倍;同时,爆破孔深度、位置和气爆压力的大小也是影响渗透率变化的重要因素。实验结果为气爆技术的实际应用提供了数据支持。   相似文献   

农村居民点整理潜力综合修正与测算——以北京市平谷区为例   总被引：26，自引：1，他引：25  

曲衍波  张凤荣  宋伟  梁发超  姜广辉 《地理学报》2012,67(4):490-503

准确测算农村居民点整理增加耕地潜力是科学编制农村土地整治规划的重要前提.本研究针对当前普遍使用的人均建设用地标准法存在计算简单、测算结果偏离实际等问题,以北京市平谷区为例,统筹考虑农村居民点整理的自然适宜性、生态安全性、经济可行性、社会可接受性和规划导向性5 个方面的因素,建立了潜力逐级修正的测算模型.测算模型的相关修正系数利用农用地分等方法、生态用地一票否决制、经济社会指标评价以及概念赋值等方法设定.研究表明,平谷区各乡镇自然适宜性修正系数为0.4757~0.8628,生态安全性修正系数为0.3004~0.8852,经济可行性修正系数为0.3943~0.8939,社会可接受性修正系数为0.4643~0.8165,规划导向性修正系数为0.2877~0.8858,生态安全性和规划导向性因素对农村居民点整理潜力影响的区域差异较其他3 个方面更加显著;潜力经过综合修正后,平谷区农村居民点整理可净增加耕地面积为614.13 hm2,增加耕地系数为10.77%.  相似文献   

基于光纤传感技术静压桩承载力时效性机理分析   总被引：1，自引：0，他引：1  

寇海磊  张明义  刘俊伟 《岩土力学》2013,34(4):1082-1088

在桩身预埋FBG（fiber bragg gating）光纤传感器,利用静压桩隔时复压试验的优势,观测开口PHC管桩的承载力、桩端阻力以及桩侧摩阻力随休止时间的变化情况。试验表明,桩极限承载力在沉桩结束一定时间范围内随时间大致呈对数型增长,沉桩284 h后提高幅度达140%,时效性系数为0.52;桩端阻力和桩侧摩阻力在休止期内的提高幅度分别为6.28%和475.37%,说明试验场地条件下试桩承载力的提高主要源于桩侧摩阻力。试验结果显示,桩极限承载力及桩侧摩阻力的发展符合3阶段增长模型,时间界点分别为21.5 h和279 h。研究成果可为基桩时效性研究及相关设计提供依据。  相似文献   

黄土高原粮食生产中的水土保持耕作技术     

彭珂珊 《云南地理环境研究》1999,11(2):68-75

在对黄土高原的农业生产综合考察分析的基础上, 结合国内外旱地农业研究进展,针对黄土高原粮食开发过程中的主要限制因子, 因地制宜提出了重视工程措施、广泛应用林草措施、优化耕作措施、挖掘农业措施的具体政策, 可使该区域粮食生产与生态环境同步发展, 可供决策部门在制订计划时参考。  相似文献