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61.
The main features of upper atmosphere dynamics as an important part of upper atmosphere climatology are presented. The dynamics
of the mesosphere and lower thermosphere (MLT) are of special interest. The results are based on the long series of investigations
in East Siberia and data from a world-wide network of observatories. We present the regional climatic norms for the prevailing
wind and semi-diurnal tide and the main features of the quasi-periodic structure of the wind field. The non-zonality of MLT
dynamics is demonstrated as well as regional differences in the response of the wind field to stratospheric disturbances,
solar activity variations and geomagnetic storms. 相似文献
62.
The so called Upper Río Negro Valley in Argentina is one of the most important fruit and vegetable production regions of the country. It comprises the lower valleys of the Limay and Neuquén rivers and the upper Negro river valley. Out of the 41,671 cultivated hectares, 84.6% are cultivated with fruit trees, especially apple, pear and stone fruit trees. Late frosts occurring when trees are sensitive to low temperatures have a significant impact on the regional production. This study presents an analysis of air flow characteristics in the Upper Río Negro Valley and its relationship with ambient air flow. To such effect, observations made when synoptic-scale weather patterns were favorable for radiative frosts (light wind and clear sky) or nocturnal temperature inversion in the lower layer were used. In the Negro river valley, both wind channeling and downward horizontal momentum transport from ambient wind were observed; in nighttime, very light wind events occurred, possibly associated with drainage winds from the nearby higher levels of the barda. In the Neuquén river valley, the prevailing effect appeared to be forced channeling, consistent with the results obtained in valleys where the synoptic scale wind crossed the axis of the valley. In the Limay river valley, the flow was observed to blow parallel to the longitudinal valley axis, possibly influenced by pressure gradient and forced channeling. 相似文献
63.
Massimiliano Burlando Emilia Georgieva Corrado F. Ratto 《Boundary-Layer Meteorology》2007,125(2):389-397
The planetary boundary-layer (PBL) parameterization is a key issue for the definition of initial wind flow fields in diagnostic
models. However, PBL theories usually treat separately stable, neutral, and convective stability conditions, so that their
implementation in diagnostic wind models is not straightforward. In the present paper, an attempt is made to adopt a comprehensive
PBL parameterisation, covering stable/neutral and unstable atmospheric conditions, which appears suitable to diagnostic models.
This parameterisation is implemented into our diagnostic mass-consistent code. A validation of the consistency between the
implemented PBL parameterisations has been checked through an analysis of the sensitivity of the vertical wind profiles to
atmospheric stability. 相似文献
64.
现代以色列经济是外向型经济。90年代以来,中东和平进程在前进,以色列经济在发展,工党政府和利库德集团政府都把进一步改革开放、奠定以色列的中东经济强国地位作为主要目标,为此,制定了推进私有化、吸引外资、扩大对外贸易的政策以及一系列相关政策,对以色列经济的现状和将来有着重大影响,也对中东区域经济的发展有着促进作用,同时也存在着某些问题。 相似文献
65.
当均匀的纬圈风应力作用于赤道海洋时,在东、西边界附近由于平衡的物理过程不同,其响应特征也不同。当盛吹一个方向的风时,例如东风,东边界的温跃层会变浅(冷水),而西边界的温跃层变深。当东风吹了t0时间而改吹西风时,无论东边界的温跃层还是西边界的温跃层都要持续到2t0时间后,才改变其发展方向。这表明边界上的物理场带有长的“惯性”或长的“记忆”。但西边界信号向东传播的速度比东边界向西传播的速度要快,且振幅也大,从这个意义上讲,ElNino事件先兆从西边界附近出现后,能迅速影响到西、中太平洋,也即西边界附近更易成为ElNino事件的源地,特别是强的ElNino事件。 相似文献
66.
67.
Li-Xin Li 《Monthly notices of the Royal Astronomical Society》2007,375(1):240-256
Recently, a soft blackbody component was observed in the early X-ray afterglow of GRB 060218, which was interpreted as shock breakout from the thick wind of the progenitor Wolf–Rayet (WR) star of the underlying Type Ic supernova 2006aj. In this paper, we present a simple model for computing the characteristic quantities (including energy, temperature and time duration) for the transient event from the shock breakout in Type Ibc supernovae produced by the core-collapse of WR stars surrounded by dense winds. In contrast to the case of a star without a strong wind, the shock breakout occurs in the wind region rather than inside the star, caused by the large optical depth in the wind. We find that, for the case of a WR star with a dense wind, the total energy of the radiation generated by the supernova shock breakout is larger than that in the case of the same star without a wind by a factor of >10. The temperature can be either hotter or colder, depending on the wind parameters. The time duration is larger caused by the increase in the effective radius of the star due to the presence of a thick wind. Then, we apply the model to GRB 060218/SN 2006aj. We show that, to explain both the temperature and the total energy of the blackbody component observed in GRB 060218 by the shock breakout, the progenitor WR star has to have an unrealistically large core radius (the radius at optical depth of 20), larger than 100 R⊙ . In spite of this disappointing result, our model is expected to have important applications to the observations on Type Ibc supernovae in which the detection of shock breakout will provide important clues to the progenitors of Type Ibc supernovae. 相似文献
68.
广东水产品出口下滑的原因分析与对策措施 总被引:6,自引:0,他引:6
高维新 《广东海洋大学学报》2007,27(5):6-10
分析广东水产品出口出现下滑趋势外部原因为:发达国家对农产品进口实行贸易壁垒,贸易保护主义有所抬头;内部原因为:国内生产经营过度分散,产业结构不合理,缺乏国际市场竞争力。提出发挥政府、企业和行业协会的积极作用,建立多元化的出口市场体系等措施,以进一步扩大广东水产品的出口,实现渔民增收、企业增效的目标。 相似文献
69.
Roland Walter 《Astrophysics and Space Science》2007,309(1-4):5-9
INTEGRAL is operational since more than three years and producing high quality data that allows to detect fainter new hard
X-ray sources. The new sources, identified until now, are mostly active galactic nuclei and absorbed or transient high mass
X-ray binaries. TeV emission could be expected from the new high mass X-ray binaries accreting dense clumps of stellar wind.
INTEGRAL sources with TeV counterparts are discussed.
Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially
the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation
of Russia and the USA. 相似文献
70.
《Marine Policy》2015
Following the decision in 2007 by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) to include European eel Anguilla anguilla on its Appendix II, and the 2010 ban of all eel exports by EU member states, a shift has occurred to tropical Asian eel species to meet the demand from East Asia. Here the focus is on the role Indonesia played in fulfilling this demand using official export figures, reports in the Indonesian media and government documents. Despite Indonesia first putting in place restrictions on the export of eel in 1974 the export has increased exponentially over the last 25 years. Prior to the EU ban it exported ~1.4 million kg/year. With the infrastructure in place, and close trade links to East Asia, and helped by government encouragement, Indonesia was in an excellent position to step in where the EU posed restrictions. Exports increased to 3.2 million kg/year (2007–2009), to 4.0 million kg/year (2010–2012), and to 6.1 million kg (2013). The interest in eel trade in Indonesia increased in parallel with the exports. From 2010 onwards the searches for the Indonesian equivalent of eel (“ikan sidat”) became frequent enough for it to be picked up by Google Trends. Indonesia is home to five species of eel, and while it is unclear in what quantities each is traded, Indonesian media reports suggest that the majority comprises A. bicolar and A. marmorata. More stringent management schemes, possibly including CITES-listing, and better monitoring are needed to ensure that international trade is not an impediment to the conservation of tropical eels. 相似文献