夜间低空急流的分析研究   总被引：3，自引：0，他引：3  

李兴生  叶卓佳  刘林勤 《大气科学》1981,5(3):210-317

本文利用北京325米气象塔取得的连续观测资料,分析了1979年9月5日夜间低空急流风温场的时空演变过程,这种低空急流的极值在夜间达到最大,其极值位置与逆温层顶的生长密切配合。低空急流是超地转的,超地转气流有一个惯性振荡周期。 低空急流的发展是起伏式的。急流的消散较快,当Ri ≤0.25达到切变不稳定的临界条件时加速崩溃。  相似文献   

²²⁶Ra distribution in the Antarctic Ocean     

Teh-Lung Ku  Mu-Ching Lin 《Earth and Planetary Science Letters》1976,32(2):236-248

²²⁶Ra data on eleven vertical profiles taken during the GEOSECS program from the Antarctic Ocean and its vicinity in both the Atlantic and the Pacific are presented. Replicate measurements were made on each sample using the Rn-emanation method. The precision (1 σ) based on triplicate analyses averages about ±2.5%. Waters all around the Antarctic continent below 2 km depth appear to exhibit a uniform²²⁶Ra concentration of 21.5 ± 1dpm/100kg, except perhaps locally such as the Ross Sea and the Drake Passage where small variations may be present. Higher in the water column, the²²⁶Ra contents decrease toward the surface with gradients which vary as a function of the influence exerted by the Antarctic Convergence. Across this oceanic front, a north-to-south increase of²²⁶Ra occurs (the increase being the largest near the surface: from 8 to 18 dpm/100 kg), reflecting the combining effect of deep-water upwelling and meridional water mixing. The core layer of the Antarctic Intermediate Water contains about 14 dpm/100 kg of²²⁶Ra and that of the Circumpolar Intermediate Water (O₂ minimum and local T maximum) about 18 dpm/100 kg. To a first approximation,²²⁶Ra covaries with Si in the circumpolar waters.  相似文献   

江淮气旋发生发展和暴雨过程及有关预报问题的研究   总被引：3，自引：0，他引：3  

黄士松  林元弼  韦统健 《大气科学》1976,(1):27-41

本文就一次典型过程作为例子,分析了江淮气旋发生发展和暴雨过程的特点,指出有利于江淮气旋发生发展的高空天气形势,地面一些中尺度低压和暴雨核的演变与气旋发展的互相联系。发现气旋区内可存在若干个中尺度低压,这些中尺度低压可先于或后于暴雨核生成而出现,并可增强、减弱或合并。文中计算了潜热释放的加热对涡度制造的贡献,指出潜热加热对气旋发展起着极为重要的作用。作者对于影响气旋发展的因子进行了讨论,并对如何根据湿度场、流场和降水分布(或卫星云图)特征来预报江淮气旋提出建议。  相似文献   

一次强飑线的中分析     

杨国祥  叶蓉珠  林兆丰 《大气科学》1977,1(3):206-213

本文对一次强飑线过程进行分析,指出高空“阶梯槽”的出现是这次飑线过程大尺度环流背景的重要特征。在此背景下,苏北和山东广大地区,有一支西南低空急流输送水汽和热量,大气层结趋于不稳定,为鼬线发展提供了不稳定能量,而高空疏散槽为不稳定能释放的一种触发机构。在飑线过境前,大气的层结在800毫巴附近的强下沉逆温,对不稳定能的储存和积累有重要意义。 这次飑线发展如此之强,除一般所说的一些条件之外,同飑线内部对流云体的合并以及与其它天气系统的碰头有密切关系;另外,中低空之间的强垂直风切变也有特殊作用。  相似文献   

Impact of climate change on 24‐h design rainfall depth estimation in Qiantang River Basin,East China     

Yue‐Ping Xu  Xujie Zhang  Ye Tian 《水文研究》2012,26(26):4067-4077

The frequency and magnitude of extreme meteorological or hydrological events such as floods and droughts in China have been influenced by global climate change. The water problem due to increasing frequency and magnitude of extreme events in the humid areas has gained great attention in recent years. However, the main challenge in the evaluation of climate change impact on extreme events is that large uncertainty could exist. Therefore, this paper first aims to model possible impacts of climate change on regional extreme precipitation (indicated by 24‐h design rainfall depth) at seven rainfall gauge stations in the Qiantang River Basin, East China. The Long Ashton Research Station‐Weather Generator is adopted to downscale the global projections obtained from general circulation models (GCMs) to regional climate data at site scale. The weather generator is also checked for its performance through three approaches, namely Kolmogorov–Smirnov test, comparison of L‐moment statistics and 24‐h design rainfall depths. Future 24‐h design rainfall depths at seven stations are estimated using Pearson Type III distribution and L‐moment approach. Second, uncertainty caused by three GCMs under various greenhouse gas emission scenarios for the future periods 2020s (2011–2030), 2055s (2046–2065) and 2090s (2080–2099) is investigated. The final results show that 24‐h design rainfall depth increases in most stations under the three GCMs and emission scenarios. However, there are large uncertainties involved in the estimations of 24‐h design rainfall depths at seven stations because of GCM, emission scenario and other uncertainty sources. At Hangzhou Station, a relative change of ?16% to 113% can be observed in 100y design rainfall depths. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A systematic approach to the input determination for neural network rainfall–runoff models     

Gwo‐Fong Lin  Guo‐Rong Chen 《水文研究》2008,22(14):2524-2530

Input determination has a great influence on the performance of artificial neural network (ANN) rainfall–runoff models. To improve the performance of ANN models, a systematic approach to the input determination for ANN models is proposed. In the proposed approach, the irrelevant inputs are removed. Then an adequate ANN model, which only includes highly relevant inputs, is constructed. Unlike the trial‐and‐error procedure, the proposed approach is more systematic and avoids unnecessary trials. To demonstrate the effectiveness of the proposed approach, an application to actual typhoon events is presented. The results show that the proposed ANN model, which is constructed by the proposed approach, has advantages over those obtained by the trial‐and‐error procedure. The proposed ANN model has a simpler architecture, needs less training time, and performs better. The proposed ANN model is recommended as an alternative to existing rainfall–runoff ANN models. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Effect of NH4-non the pigment content ofLaminaria japonica     

Dong Liangfeng  Lin Guangheng  Wu Chaoyuan 《中国海洋湖沼学报》1990,8(2):128-134

Experiments withLaminaria japonica were conducted in Meidao Bay and Pier Bay, Qingdao, China, Nitrogen-starved plants were fertilized intermittently with 7.1 mM NH₄−N solution for 1 hour at 3 day intervals, after which chlorophyll a, fucoxanthin, chlorophyll c and β-carotene contents were analyzed. Photosynthetic and growth rates of plants and nitrogen content of seawater were determined. their contents of chlorophyll a, fucoxanthin, chlorophyll c and β-carotene were 1.65, 0.67, 0.33 and 0.06 mg.dm⁻² respectively, or 2.46, 2.03, 1.86 and 1.81 times those of the controls. The ratio of fucoxanthin to chlorophyll a in nitrogen-enriched plants was lower than that of the controls. Normal growth rate of the plants (2 cm·day⁻¹ in length) were reached when the chlorophyll a content exceeded 0.1 mg·g⁻¹ fresh wt., indicating that chlorophyll a content can serve as an indicator of normal growth. Experimental results show that seawater is regarded as fertile for the normal growth ofLaminaria if the total inorganic nitrogen (including ammonium salt, nitrate and nitrite) content in seawater is about 2 μm, and infertile if less than 1 μm, in which case fertilizer should be applied. Contribution No. 1703 from the Institute of Oceanology, Academia Sinica  相似文献   

GROUNDWATER QUALITY AND CONTAMINATION INDEX MAPPING IN CHANGCHUN CITY, CHINA   总被引：13，自引：0，他引：13  

Hamadoun BOKAR 《中国地理科学(英文版)》2004,14(1):63-70

1INTRODUCTIONGroundwater in Changchun City assures about 45% of total water supply. Drinking water supply of Chang-chun City was mostly served by surface water from Shitoukoumen and Xinlicheng reservoirs located in the east and south of the city (ZHANG, 1993). However, with the development of urban construction the ground-water especially from deep boreholes is also used for drinking purpose in suburban areas. The urbanization process in Changchun City threatens the groundwater quali…  相似文献   

Variations of b‐values at the western edge of the Ryukyu Subduction Zone,north‐east Taiwan     

Jing‐Yi Lin  Jean‐Claude Sibuet  Shu‐Kun Hsu 《地学学报》2008,20(2):150-153

Using earthquakes relocated in north‐east Taiwan, we estimated b‐value distribution along a cross‐section located near the Ryukyu slab edge, and four b‐value anomalous areas are evidenced: (1) a high b‐value body lying on top of a low Vp, low Vs and high Vp/Vs sausage‐like body was considered as a region of enhanced partial melt or water supply above which seismicity occurs; (2) beneath the Ilan Plain, an anomalous area characterized by b‐values slightly higher than 1.1 might give evidence to the magma conduits to the Kueishantao Island; (3) above the Ryukyu Wadati‐Benioff zone, at depths ranging from 90 to 110 km, a high b‐value anomaly might correspond to the depth where dehydration occurs in the subducting oceanic plate; and (4) a low b‐value area located within the Ryukyu slab, at depths ranging from 70 to 90 km, might be linked to the compressive mechanisms shown by focal mechanisms and the bending of the subducting plate.  相似文献   

红旗连锁顾客满意度测评与改进措施研究     

万梅  李琳  钱永贵 《成都信息工程学院学报》2007,22(Z1):152-156

顾客满意状态与企业利润率之间有着密切的联系,提高顾客满意度成了许多企业的重要经营目标.对红旗连锁的现状进行了分析,确定顾客满意度的各项指标与权重,建立了一个完善的指标和级度体系,通过对红旗连锁的顾客展开调查,综合评价了顾客现有的满意程度,并提出了提高顾客满意度的途径.  相似文献