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71.
The aim of this paper is to show a climatology of Mesoscale Convective Systems (MCS) in the NE of the Iberian Peninsula, on the basis of meteorological radar observations. Special attention was paid to those cases that have produced heavy rainfalls during the period 1996–2000. Identification of the MCS was undertaken using two procedures. Firstly, the precipitation structures at the lowest level were recognised by means of a 2D algorithm that distinguishes between convective and non-convective contribution. Secondly, the convective cells were identified using a 3D procedure quite similar to the SCIT (Storm Cell Identification and Tracking) algorithm that looks for the reflectivity cores in each radar volume. Finally, the convective cells (3D) were associated with the 2D structures (convective rainfall areas), in order to characterize the complete MCS. Once this methodology was presented the paper offers a proposal for classifying the precipitation systems, and particularly the MCS. 57 MCS structures were classified: 49% of them were identified as linearly well-organised systems, called TS (39%), LS (18%) and NS (43%). In addition to the classification, the following items were analysed for each MCS found: duration, season, time of day, area affected and direction of movement, and main radar parameters related with convection. The average features of those MCS show an area of about 25000 km2, Zmax values of 47 dBz, an echotop of 12 km, the maximum frequency at 12 UTC and early afternoon and a displacement towards E-NE. The study was completed by analysing the field at surface, the presence of a mesoscale low near the system and the quasi-stationary features of three cases related with heavy rainfalls. Maximum rainfall (more then 200 mm in 6 h) was related with the presence of a cyclone in combination with the production of a convective train effect. 相似文献
72.
73.
Seasonal variation in abundance and species composition of a planktonic diatom assemblage distributed in the water column and also settled on the bottom was investigated for the shallow coastal water in Matsushima Bay on the Pacific coast of northeastern Japan during the period from October 1999 to September 2000. A spring bloom of diatoms began in April when nutrient concentrations started to increase, indicating the importance of nutrients. Viable cells of Skeletonema costatum and Thalassiosira spp., which were the dominant species in the water column throughout the year, were also always abundant in the bottom sediment. Both populations in the water column and on the bottom fluctuated essentially in parallel. For the planktonic diatoms in shallow coastal waters to maintain their vegetative populations in the water column, it would be advantageous for them to have a seeding population of viable cells on the bottom that are easily resuspended into the upper photic layer. 相似文献
74.
We carry out a study of the interaction between electromagnetic fields produced innature and cells with no structure but with different shapes and sizes, considered asapproximations of those observed in the human body. Magnetic fields produced byvarious atmospheric and geomagnetic phenomena are compared with the fieldsgenerated by the cells themselves. Working with frequencies up to 105 Hz, we found that in most cases lightning is the natural phenomena capable of producingfield intensities comparable to those generated by the cells. As a first approximationwe assume that a cell might be affected only if a field of intensity comparable to thecell's field is present. Oscillating fields of less intensity and their harmonics can involveresonant interactions with the cells, however this situation is not considered here. Under the approximation of our study we found that the size and the shape are parameters of paramount importance: lightning represents a natural hazard only for the largest cells, while the quadrangular cells are not affected by any of the natural phenomena considered here. 相似文献
75.
A. M. de S. Bueno C. A. de B. Pereira M. N. Rabello-Gay J. M. Stern 《Stochastic Environmental Research and Risk Assessment (SERRA)》2002,16(4):267-278
The data analyzed in this paper are part of the results described in Bueno et al. (2000). Three cytogenetics endpoints were
analyzed in three populations of a species of wild rodent – Akodon montensis – living in an industrial, an agricultural, and
a preservation area at the Itajaí Valley, State of Santa Catarina, Brazil. The polychromatic/normochromatic ratio, the mitotic
index, and the frequency of micronucleated polychromatic erythrocites were used in an attempt to establish a genotoxic profile
of each area. It was assumed that the three populations were in the same conditions with respect to the influence of confounding
factors such as animal age, health, nutrition status, presence of pathogens, and intra- and inter-populational genetic variability.
Therefore, any differences found in the endpoints analyzed could be attributed to the external agents present in each area.
The statistical models used in this paper are mixtures of negative-binomials and Poisson variables. The Poisson variables
are used as approximations of binomials for rare events. The mixing distributions are beta densities. The statistical analyzes
are under the bayesian perspective, as opposed to the frequentist ones often considered in the literature, as for instance
in Bueno et al. (2000). 相似文献
76.
A NUMERICAL EXPERIMENT STUDY ON THE FORMING MECHANISMS OF LOW-LATITUDE CIRCULATION CELLS AND PRECIPITATION DURING AN EAST ASIAN COLD SURGE 下载免费PDF全文
The forming mechanisms of low-latitude circulation cells and precipitation during an East Asian cold surge have been studied by using a five-layer primitive equation model.Numerical experiments show that in mid-high latitudes,the propagation of the East Asian winter monsoon is nearly a dry process;in low-latitudes,the effects of cumulus convection intensify the northeast monsoon and northeast trade wind;however,they also prevent the intertropical convergence zone(ITCZ) from further southward invasion,and strengthen the meridional and zonal cells over East Asia. Numerical results also indicate that the winter monsoon precipitation in Indonesia and Northern Australia can exist independently.Both the South China Sea(SCS) cold surge and the West Pacific northeast cross-equatorial trade wind are of importance for the formation of the Northern Australia summer monsoon and its precipitation.Numerical results show that the development of cumulus convection,triggered by the SCS cold surge,is a crucial factor in forming the heavy monsoon precipitation and low-level stationary disturbances in Indonesia and Borneo.The tropical topography and northeast trade wind disturbances only affect the intensity of precipitation there. 相似文献
77.
康定县地热资源丰富,但开发利用少,仅2008-2009年由四川省地质工程勘察院在中谷地区实施地热勘探井2口,钻探深度共计184.96m。DZK02井是部署在四川省雅拉河中上游热水塘区块地热资源大盖沟沟口雅拉河右岸一级阶地上的第一口预探井,设计井深2 000m。钻井施工主要面临地层倾角大、地层出水量大、温度高、岩性破碎等施工难题。施工队伍采用螺杆纠斜、清水控压等钻井工艺,圆满完成了该井的施工任务。为该地区地热水的开发利用进行了有益的尝试。 相似文献
78.
定常情况下,本文利用球坐标系(λ,φ,r)的动力、热力学方程导出三维速度场(vλ,vφ,vr)的动力系统.这种包括摩擦力和热传导的不可压缩大气运动的动力系统,无论从定性上还是从定量上都能描述由赤道和极地间的加热不均匀造成的三圈环流.定性上表明,在北半球经向速度vφ和纬向速度vλ同符号,地表刮北风(vφ<0)和刮东风(vλ<0)相对应,刮南风(vφ>0)和刮西风(vλ>0)相对应.在南半球,经向速度vφ和纬向速度vλ符号相反,刮北风(vφ<0)和刮西风(vλ>0)相对应,刮南风(vφ>0)和刮东风(vλ<0)相对应.定量分析表明球面上的压力场p可以用球调和函数plm(sinφ)cosmλ来表达.当取l=6,m=0时即可导出三圈环流.在经圈剖面(φ,r)上,地表的φ1=±56°和φ2=±28°左右,以及赤道是速度场的奇点,它们都是鞍点,说明在副热带是下沉运动,在中纬度是上升运动,这正是三圈环流中的Ferrel环流的特征.这样经向速度vφ和纬向速度vλ相联系,经向速度vφ又和垂直速度相联系,那么三圈环流的三维速度场就构成了一个整体. 相似文献
79.
《海洋科学》2012,36(1)
以日本七鳃鳗(Lampetrajaponica)为研究对象,观察其外周血细胞显微结构和探讨类淋巴细胞原代培养条件。采用Wright氏和Giemsa氏染色法对日本七鳃鳗外周血液有形成分进行显微观察,可鉴别出红细胞、淋巴细胞、中性粒细胞、单核细胞、嗜酸性粒细胞:未发现嗜碱性粒细胞。通过Ficoll密度梯度离心法和流式细胞仪分选获得高纯度的七鳃鳗类淋巴细胞。经条件优化后确定最适培养液L15+20%FBS(5%七鳃鳗血清)+0.46%NaCl,在18℃,pH6.8~7.0的条件下对日本七鳃鳗类淋巴细胞进行体外培养,大多数类淋巴细胞半贴壁生长,细胞状态较好,最长可以存活近一个月。类淋巴细胞的原代培养为日本七鳃鳗细胞体外培养的深入研究提供了实验依据。 相似文献
80.