Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Analysis of the ionospheric storm during 19~22 March 2001

SUN Ling-feng,MAO Tian,WAN Wei-xing,ZHAO Bi-qiang,

地球物理学进展 , 2009,
Abstract: In this paper, using the observational data of ACE satellite, ionosonde and GPS TEC, the authors analyze the ionospheric storm during 19~22 March 2001. The results show that the interplanetary environment induced by the coronal mass ejection (CME) provides the large scale background for the ionospheric storm. The strong negative ionospheric storm occurs in the recovery phase of the geomagnetic storm.And the mechanism of the negative ionospheric storm is consistent with the storm ring theory.
Analysis of Temperature Fluctuations during a Dust Storm

XIE Liang,ZHANG Jing-hong,

中国沙漠 , 2011,
Abstract: Near surface wind velocity and temperature at 0.5 m,1.0 m,8.0 m and 16 m were measured during a dust storm in Minqin in April 24,2010,and the measuring frequency of wind velocity and temperature was all 50 Hz.Measurement results show that the dust storm presented a severe dust storm type during the first two hours,then into dust storm type.The wind speed during April 24 to 27 underwent three stages which contained an increasing period,a contemporary stable period and a decreasing period.Analysis of the wind...
Quantitative Study on Influencing Factors of Desertification in Minqin County, Gansu Province

JIANG Zhi-rong,AN Li,CHAI Cheng-wu,
,安 力,柴成武

中国沙漠 , 2008,
Abstract: Based on survey to influencing factors of desertification in Minqin county of Gansu province, the following eleven indexes are determined, they are rural population, cultivated area, grain output, forestation area, amount of electromechanical well, wheat yield, rural power consumption, groundwater mineralization degree, inflow from upper river, sand-dust storm days, and annual precipitation. The inner structure of each factor and its effect on desertification process are analyzed by method of factor analysis. The result showed that the contribution of anthropogenic factor to desertification is 82 %, and that of the natural is 18 %.
Cluster mission and data analysis for the March 2001 magnetic storm
F. Frutos Alfaro,A. Korth,M. Fr?nz,C. G. Mouikis
Geofísica internacional , 2004,
Abstract: The Cluster mission is intended for the study of the Earth’s magnetosphere and Sun-Earth relationships. Four satellites fly in a tetrahedral formation sending data that can separate spatial from temporal effects for the first time. This formation will provide a better understanding of microscopic and macroscopic features in the magnetosphere and the solar wind. As an illustration we discuss the CIS data during a large magnetic storm.
Austral electrojet indices derived for the great storm of March 1989 1177
V. M. Silbergleit,M. M. Zossi de Artigas,J. R. Manzano
Annals of Geophysics , 1996, DOI: 10.4401/ag-4046
Abstract: Available magnetic records from eight stations in the Antarctica, for the March 1989 geomagnetic storm, are used to construct the southern hemisphere auroral indices, analogous to the boreal ones. The results show a diurnal variation depending on the distribution of the stations. An acceptable correlation between the northern and southern hemisphere indices are found except for the index indicating the presence of the eastward auroral electrojet. However, differences in the amplitudes of both auroral electrojet indices were observed.
Ionospheric convection during the magnetic storm of 20-21 March 1990  [cached]
J. R. Taylor,T. K. Yeoman,M. Lester,M. J. Buonsanto
Annales Geophysicae (ANGEO) , 2003,
Abstract: We report on the response of high-latitude ionospheric convection during the magnetic storm of March 20-21 1990. IMP-8 measurements of solar wind plasma and interplanetary magnetic field (IMF), ionospheric convection flow measurements from the Wick and Goose Bay coherent radars, EISCAT, Millstone Hill and Sondrestrom incoherent radars and three digisondes at Millstone Hill, Goose Bay and Qaanaaq are presented. Two intervals of particular interest have been identified. The first starts with a storm sudden commencement at 2243 UT on March 20 and includes the ionospheric activity in the following 7 h. The response time of the ionospheric convection to the southward turning of the IMF in the dusk to midnight local times is found to be approximately half that measured in a similar study at comparable local times during more normal solar wind conditions. Furthermore, this response time is the same as those previously measured on the dayside. An investigation of the expansion of the polar cap during a substorm growth phase based on Faraday's law suggests that the expansion of the polar cap was nonuniform. A subsequent reconfiguration of the nightside convection pattern was also observed, although it was not possible to distinguish between effects due to possible changes in By and effects due to substorm activity. The second interval, 1200-2100 UT 21 March 1990, included a southward turning of the IMF which resulted in the Bz component becoming -10 nT. The response time on the dayside to this change in the IMF at the magnetopause was approximately 15 min to 30 min which is a factor of ~2 greater than those previously measured at higher latitudes. A movement of the nightside flow reversal, possibly driven by current systems associated with the substorm expansion phases, was observed, implying that the nightside convection pattern can be dominated by substorm activity.
Comparison on changes and theri driving forces of farmland in oases of middle and lower reaches: The case of Liangzhou and Minqin oases in the Shiyang river basin

LI Xiao-Yu,XIAO Du-Ning,HE Xing-Yuan,CHEN Wei,HU Zhi-Bin,SONG Dong-Mei,

生态学报 , 2006,
Abstract: The development and utilization of water and land resources in the Shiyang river basin is the highest among the 3 inland rivers in the Hexi Corridor of Gansu province, northwestern China. Based on field investigation and social-economical data, in combination with TM images of the study area in 1986 and 2000, this paper analyzed the changes of farmland and their driving forces in Liangzhouqu and Minqin oases in the middle and lower reaches of Shiyang river basin in the last 20 years. Farmland increased in both oases, while Minqin oasis increased more quickly. Most of the increased farmland was distributed on desert-oasis ecotones. But it was mainly converted from desert in Liangzhou oasis, and from woodland and grassland in Minqin oasis. In view of driving forces, the population increase was one of the most important factors, and improvement of agricultural technique and economic development provided conditions for farmland expansion in both oases. In addition, the expansion of farmland was closely related to the amount of surface water in Liangzhou oasis, but was effected by ecological environment such as gale and dust storm, and weather conditions such as rainfall and evaporation in Minqin oasis. With the development of human activities and expansion of farmland in Liangzhou oasis, the need for surface water is ever-growing from year to year, resulting in a decrease of annual discharge to the Hongyashan reservoir from 5×108 m3 during the 1950s and 1960s to only 1.0×108 m3 or so at present. Therefore overuse of groundwater in these regions, especially in the downstream Minqin oasis is very notable. All these indicated that the development of oases in the middle and lower reaches of Shiyang River had already lost the balance to a great extent, and the economic increase of Liangzhouqu oasis is at the cost of environment deterioration of Minqin oasis.In order to realize rational resource utilization and sustainable development of Shiyang river basin, the surface water should be allotted at a reasonable proportion in the whole watershed, recovering the runoff in the lower reaches to 18% of the total runoff (about 2.5×108m3/a) of Shiyang river, which used to be the level in early 1980s. In addition, the charge for transfer of water from other watersheds should be allocated according to the proportion of runoff utilization, and thus reduce the cost of water use in the lower reaches such as Minqin Oasis.
Longitudinal differences observed in the ionospheric F-region during the major geomagnetic storm of 31 March 2001
D. Pallamraju, S. Chakrabarti,C. E. Valladares
Annales Geophysicae (ANGEO) , 2004,
Abstract: We describe the effect of the 6 November 2001 magnetic storm on the low latitude thermospheric composition. Daytime red line (OI 630.0nm) emissions from Carmen Alto, Chile showed anomalous 2-3 times larger emissions in the morning (05:30-08:30 Local Time; LT) on the disturbed day compared to the quiet days. We interpret these emission enhancements to be caused due to the increase in neutral densities over low latitudes, as a direct effect of the geomagnetic storm. As an aftereffect of the geomagnetic storm, the dayglow emissions on the following day show gravity wave features that gradually increase in periodicities from around 30min in the morning to around 100min by the evening. The integrated dayglow emissions on quiet days show day-to-day variabilities in spatial structures in terms of their movement away from the magnetic equator in response to the Equatorial Ionization Anomaly (EIA) development in the daytime. The EIA signatures in the daytime OI 630.0nm column-integrated dayglow emission brightness show different behavior on days with and without the post-sunset Equatorial Spread F (ESF) occurrence.
Discussion on Ecological Effect and Reasonable Control of Sand-dust Storm

NA Ren-hua,GAO Run-hong,ZHANG Ming-tie,

中国沙漠 , 2007,
Abstract: Sand-dust storm is a natural phenomenon that happened in particular space and particular time,its happening frequency and intensity have been accumulated and strengthened under the excessive interference of mankind.People are very afraid of the harming of sand-dust storms.However,sand-dust storms also bring some important ecological effect on the global and regional eco-environment.They can promote the biogeochemical cycle of the global eco-system,redistribute and balance the productivity of the earth ecosystem,improve atmosphere environment, accelerate the biological breed disperse and the eco-system succession.We should not only pay attention to the harming of sand-dust storms in source region and passing routes,but also strengthen the study on the following aspects: the impact of sand-dust storms on energy flow,nutrient flow and communication flow of ecosystem;impact on vegetation restoration,crops cultivation and regional climate;the study on single pollution of sand-dust storm and the accumulated pollution caused by sand-dust storm and these cities that have pollution sources;the study on the balance point between sand-dust storm harming and its happening frequency,and the balance point between economic loss and ecological effect.Therefore,we should endue the scientific attitude on this phenomenon and carry through the ecological management rationally on the source regions,complete the action of ecological rehabilitation according that we can do it or not.In the paper,the ecotone of China is divided into three areas,that is,the ecological function area,the ecological rehabilitation area and the human habitation area.Thus we should adopt different ecological management measures.
Characteristics of Atmospheric Boundary-Layer Structure and Turbulent Flux Transfer during a Strong Dust Storm Weather Process over Beijing Area

PENG Zhen,LIU Xi-Ming,HONG Zhong-Xiang,WANG Bing-Lan,

气候与环境研究 , 2007,
Abstract: Based on the mean wind,temperature and humidity data and turbulent data observed at the Beijing 325 m Meteorological Tower,and the surface conventional meteorological data and sounding data collected at Beijing Meteorology Observatory,some characteristics of atmospheric boundary layer structure and turbulence transfer during the strong dust storm weather from 18 to 22 March 2002 was investigated.The results showed that,1) before the dust storm broke out,the mean wind speed was very slow and the temperature was comparatively high.And strong inversion layers existed in the upper atmospheric boundary layer(ABL).While after the dust storm broke out,the wind speed increased sharply and the temperature changed greatly.The temperature increased sharply in advance,and then decreased continuously.Consequently the inversion layer was rapidly destroyed.2) During the initial stages of the synoptic process,there were systematic upward flows at the 280 m height in the ABL,but systematic downward flows occurred at the heights of 47 m and 120 m during the synoptic process.The turbulence energy,the momentum transportation and the sensible heat transportation were increasing sharply.The turbulence energy and the fluxes of turbulent momentum and sensible heat collected at 120 m height was larger than those collected at the heights of 47 m and 280 m,perhaps which was caused by the local circumfluence of Beijing.3) In this dust storm process,the friction velocities collected at 47 m and 120 m heights were larger than the critical friction velocity of Beijing,consequently we got the conclusion that the local dust emission is one of the important source of dust particles of Beijing in this synoptic process.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.