应重视和加强我国沙漠绿洲的研究   总被引：2，自引：1，他引：2  

文子祥  董光荣 《地球科学进展》1996,11(3):270-274

把散布在我国干旱荒漠地带内的沙漠绿洲，统一组合成一种独特而完整的生成地域单元开展研究，应予重视和加强。沙漠绿洲是干旱荒漠地带内精华地域，也是今后该地带开发建设和经济发展基地，还是改造利用沙漠的潜力与希望所在。随着我国经济发展战略重点向西北转移，开发建设和整治利用沙漠绿洲，有着特别的重要性和紧迫性。  相似文献   

南极瑞穗站上空动量和感热等湍流通量的观测研究   总被引：2，自引：0，他引：2       下载免费PDF全文

曲绍厚  山内恭 《极地研究》1989,1(4):1-11

本文根据南极瑞穗站气温、风等平均廓线资料,利用相似理论通量一廓线关系计算得出了该站的湍流通量,并与西太平洋热带海域和北京地区湍流通量计算结果进行了比较。  相似文献   

两次陕北暴雨过程热力动力机制诊断          下载免费PDF全文

赵强  王楠  李萍云  屈丽玮 《应用气象学报》2017,28(3):340-356

利用常规气象观测资料、NCEP FNL分析资料（水平分辨率为1°×1°,时间分辨率为6 h）,对2013年7月21-22日和2014年7月8-9日两次陕北暴雨过程成因进行热力动力诊断,结果表明:两次陕北暴雨与高低空急流关系密切,暴雨带位于低空急流左侧的水汽辐合区,“0721”过程低空急流更强,在高低空急流耦合的强上升运动区（延安）出现大暴雨。降水前期,两次过程大气均存在对流不稳定,切变线触发对流,产生强降水,而其释放的凝结潜热加热形成中低层大气的热力不连续面,湿斜压性及锋生增强,造成整层饱和大气的抬升,维持强降水。“0721”过程前期对流降水的潜热释放更大,由此反馈的低空急流及锋生更强,出现大暴雨天气。广义对流涡度矢量垂直分量很好地描述了两次暴雨过程高低空急流耦合作用以及凝结潜热释放增强的锋生作用,其变化趋势能够反映降水的发展和减弱过程。暴雨出现在湿热力平流参数垂直积分大值中心及南侧的高梯度区,大值中心出现后约6 h会产生强降水,这对于强降水落区的预报有一定指示意义。  相似文献   

FY 3B 1级数据质量保障技术研究     

张媛媛  屈兴之  赵现纲  贾树泽  马友  田思维 《气象科技》2017,45(1):42-46

极轨气象卫星1级遥感数据是遥感信息定量应用的基础,了解影响1级遥感数据完整性和时效性的异常现象并在最短时间内进行问题的定位和处理,可以在最大程度上保障该数据的质量。以FY-3B卫星为研究对象,根据国家卫星气象中心多年积累的运行经验,对FY-3B1级数据的质量问题进行了分类,然后从问题现象、问题原因的快速定位和处理方法等方面对1级数据的质量保障技术进行了研究。最后基于研究结果提出了地面应用系统的改进建议,从而进一步提高1级数据的质量。  相似文献   

Classification of full-polarization ALOS-PALSAR imagery using SVM in arid area of Dunhuang     

JunZhan Wang  JianJun Qu  WeiMin Zhang  KeCun Zhang 《寒旱区科学》2016,8(3):263-267

Classification is an important process in interpretation of synthetic aperture radar(SAR) imagery. As an advanced instrument for remote sensing, the polarimetric SAR has been applied widely in many fields. The main aim of this paper is to explore the ability of the full-polarization SAR data in classification. The study area is a part of Dunhuang, Gansu Province, China. An L-band full-polarization image of Dunhuang which includes quad-polarization modes was acquired by the ALOS-PALSAR(Advanced Land Observing Satellite–the Phased Array type L-band Synthetic Aperture Radar). Firstly, new characteristic information was extracted by the difference operation, ratio operation, and principal component transform based on the full-polarization(HH, HV or VH, VV) modes SAR data. Then the single-, dual-, full-polarization SAR data and new SAR characteristic information were used to analyze quantitatively the classification accuracy based on the Support Vector Machines(SVM). The results show that classification overall accuracy of single-polarization SAR data is poor, and the highest is 56.53% of VV polarization. The classification overall accuracy of dual-polarization SAR is much better than single-polarization, the highest is 74.77% of HV VV polarization data. The classification overall accuracy of full-polarization SAR is 80.21%, adding the difference characteristic information, ratio characteristic information and the first principal component(PC1) respectively, the overall accuracy increased by 3.09%, 3.38%, 4.14% respectively. When the full-polarization SAR data in combination with the all characteristic information, the classification overall accuracy reached to 91.01%. The full-polarization SAR data in combination with the band math characteristic information or the PC1 can greatly improve classification accuracy.  相似文献   

Causes and controlling pattern of sand hazards at the Danghe Reservoir of Dunhuang in Northwest China     

Sheng-bo?Xie  Jian-jun?Qu  Ying-jun?PangEmail author 《山地科学学报》2016,13(11):1973-1983

Sand hazards are serious at the Danghe Reservoir of Dunhuang,and efforts to control sand are ineffective because disaster-causing mechanisms are currently unclear.The source of sandy materials,dynamic environment of blown sand,and controlling measures of the reservoir area are investigated using different methods,such as granularity analyses,wind regime and sand transport field observation and analyses,sand drift potential calculation.Accordingly,the sandy materials are found to derive chiefly from the Mingsha Mountain on the north side of the reservoir area.In addition,sand grain in the range of 0.50-0.25 mm and 0.25-0.10 mm are dominant.The prevailing sand-moving wind originates from the N direction,accounting for 15.38% of the yearly total,which coincides in the same direction with sand source,thereby increasing the severity of sand hazards in the reservoir area.The yearly sand DP is 1386.59 VU,the yearly RDP is 567.31 VU,the yearly RDP/DP is 0.41,and the yearly RDD is 183.15°.In the windy season(mainly in summer),sand materials are blown by wind from north to south,and then blocked by the Danghe River.The sand materials then move with an approximate east-west trend into the river channel and produce sediment,thereby causing adisaster.We propose that the sand-controlling pattern of the Danghe Reservoir is dominated by sand blocking in the outer fringe and sand fixing in the inner fringe.Applying windbreak and sand fixation to control sandy material movement into the river channel plays an important role in retarding sedimentation and extending the useful life of the Danghe Reservoir.  相似文献   

长沙市城市居民宅基地转入意愿及影响因素     

瞿理铜  秦琴 《地域研究与开发》2017,36(2)

研究宅基地转入方的需求意愿及影响因素可为构建科学合理的宅基地流转制度提供参考。从需求的角度出发,构建城市居民宅基地转入意愿影响因素分析模型,以长沙市为例,运用Logistic回归模型分析了城市居民宅基地转入意愿的影响因素。结果表明:影响城市居民宅基地转入意愿的因素主要有宅基地形状、城市居民年龄、城市居民家庭住房使用年限、宅基地产权、宅基地与中心城区的距离和宅基地基础设施状况。宅基地流转应以城中村和城郊村为试点范围,加快宅基地确权颁证,完善宅基地基础设施。  相似文献   

Significant enhancement in atmospheric biweekly disturbance over Northeast Asia during the recent warming hiatus     

李桑  龚道溢  屈静玄 《Acta Meteorologica Sinica》2016,30(5):631-644

Based on daily 500-hPa geopotential height from ERA-Interim reanalysis data, this study analyzed the day-to-day circulation variance in cold season (October–March) by composite and correlation analysis. Two same-length time periods were compared, namely, the hiatus period (1999–2013) and the rapid warming period (1984–1998). Spectral analysis revealed that over the mid–high latitudes of the Northern Hemisphere, the most outstanding peak in the daily 500-hPa geopotential height variance was of quasi-biweekly timescale (about 10–20 days), accounting for about 32% of the total variance. During the warming hiatus, quasibiweekly disturbance (QBD) changed remarkably in Northeast Asia. On average, within the domain 42°–50 °N, 128°–142 °E, the QBD variance changed from 1860 m² in the rapid warming period to 2475 m² in the hiatus period, increasing by about 33% and statistically significant at the 95% confidence level. Lead–lag analysis showed that the QBD signal could be traced back by about 14 days, with an origin around the Ural Mountains. Then, the signal developed and propogated southeastward, with its location about 10 days prior to its peak in West Siberia, and about 6 days prior to its peak in the Sayan Mountains, and finally moving to Northeast Asia. By comparing the propagation process between the two periods, we found that the propagation paths were basically the same, but there were evident differences in the intensity of the signals. The intensification of QBD may have been related to the increased energy conversion from mean flow to QBD transients. The frequency of low-temperature extremes in negative QBD phases was much higher than under normal conditions or in positive phases. Associated with the enhanced QBD, the probability of extreme low temperature increased from 19% during the rapid warming period to 27% during the warming hiatus.  相似文献   

乌鲁木齐降水化学成分及来源分析     

钟玉婷  刘新春  范子昂  陆辉  何芳  屈涛 《沙漠与绿洲气象(新疆气象)》2016,10(6):81-87

降水是大气中主要和次要污染物的重要收集器,是清除大气中颗粒物和气态污染物最好的清除剂。为了了解乌鲁木齐降水特征,本文利用离子色谱分析了2010年降水样品,研究表明,该区降水pH值在5.6~7.77之间,年均值为6.19,电导率变化范围为18.7~172.5μs·cm~(-1),年均值为57.73μs·cm~(-1)。降水中主要离子浓度排序为Ca~(2+)SO_4~(2-)NH_4~+Na~+Mg~(2+)Cl~-NO_3~-K~+F~-,Ca~(2+)是最主要的阳离子,SO2-4是最主要的阴离子,表明乌鲁木齐降水中的致酸物质主要是硫酸盐。总离子浓度季节变化特征表现为秋季高,冬季低。FA平均值为0.001,表明99.9%的降水酸度被碱性成分中和,NF计算结果表明Ca~(2+)具有很强的中和能力。从相关分析、富集因子来看,SO_4~(2-)和NO_3~-主要受人为源的控制,K+主要存在于土壤扬尘或生物质燃烧产生的细颗粒物中;Mg~(2+)主要来自陆源的土壤扬尘等;Cl~-主要来自海相输入,生物质燃烧、人类生活污水排放以及化工厂排放对Cl-也有很大贡献。  相似文献   

呼伦贝尔市新旧综合气象干旱指数应用对比   总被引：1，自引：0，他引：1  

曲学斌  姚振东 《气象科技》2016,44(2):325-330

利用呼伦贝尔市4个气象台站1972—2013年逐日气象观测资料,计算逐日新的综合气象干旱指数MCI与旧的综合气象干旱指数CI,并对比两种干旱指数统计出的干旱日数、干旱强度,以及根据相应标准统计出的干旱过程和与实际干旱发生情况的吻合程度,分析新旧指数的优劣。结果表明,由于CI没有区分逐日降水量在指数中的权重,从而造成其跳变要多于MCI,而且MCI引入了近150天降水量的SPI并区分了冬、夏半年的权重值,避免了干旱指数对呼伦贝尔市冬季、初春干旱评价过重的问题。结合呼伦贝尔市实际的气候特点和干旱灾害发生实况,MCI更符合实际,适合业务应用。  相似文献