一个巨型望远镜方案   总被引：4，自引：0，他引：4  

苏定强  王亚男  崔向群 《天文学报》2004,45(1):105-114

提出一个有特色的巨型望远镜(FGT)方案．其主镜口径为30米，主焦比为1．2，由1095块圆环形子镜构成．采用地平式装置．光学系统包括Nasmyth系统、折轴(Coude)系统和一个大视场系统．提出一个由4个镜面组成的新的Nasmyth系统，在约10′的视场范围内像斑小于爱里斑，达到衍射极限．比传统的Nasmyth系统的衍射极限视场大得多．可在这样的大视场内同时作好几个小区域的衍射极限的观测．当由Nasmyth系统转换到折轴系统和大视场系统时，采用主动光学技术改变子镜的面形、倾斜和平移，产生一个新的主镜面形，使折轴系统和大视场系统都能得到很好的像质．大视场系统的视场直径25′，场曲轻微，并有可能校正大气色散．给出了子镜面形和位置的公差，并讨论了望远镜的装置和结构,方案中的特色和创新对未来大望远镜的研制有普遍意义．  相似文献   

Study on Ensemble-Based Forecast of Extremely Heavy Rainfalls in China: Experiments for July 2011 Cases          下载免费PDF全文

LIU Lin  CHEN Jing  CHENG Long  LIN Chunze  WU Zhipeng 《Acta Meteorologica Sinica》2013,27(2):170-185

According to the Anderson-Darling principle, a method for forecast of extremely heavy rainfall (abbreviated as extreme rainfall/precipitation) was developed based on the ensemble forecast data of the T213 global ensemble prediction system (EPS) of the China Meteorological Administration (CMA). Using the T213 forecast precipitation data during 2007-2010 and the observed rainfall data in June-August of 2001-2010, characteristics of the cumulative distribution functions (CDFs) of the observed and the T213 EPS forecast precipitation were analyzed. Accordingly, in the light of the continuous differences of the CDFs between model climate and EPS forecasts, a mathematical model of Extreme Precipitation Forecast Index (EPFI) was established and applied to forecast experiments of several extreme rainfall events in China during 17-31 July 2011. The results show that the EPFI has taken advantage of the tail information of the model climatic CDF and provided agreeable forecasts of extreme rainfalls. The EPFI based on the T213 EPS is useful for issuing early warnings of extreme rainfalls 3-7 days in advance. With extension of the forecast lead time, the EPFI becomes less skillful. The results also demonstrate that the rationality of the model climate CDF was of vital importance to the skill of EPFI.  相似文献   

河源市城区高温炎热的气候特征分析     

魏璐  周晓湘  郑菲菲 《广东气象》2020,(2):17-21

利用东源县和紫金县国家气象站1978-2018年的逐日气象数据,分析了河源城区高温和炎热天气特征。结果表明:河源城区总高温日数、一般高温日数和重高温日数均呈明显增加趋势,无严重高温日。总高温日数存在4~5、8~9和准15年时间尺度的周期变化。常年首次在5、6月出现高温日;高温炎热日出现次数最多在7、8月份;极端年最高气温介于36.2~39℃。炎热日数以0.26 d/年速率明显增加,同一个炎热临界值,相对湿度增大,对应的最高气温会降低。炎热日数与热岛效应强度之间存在显著性的相关关系。高温炎热过程主要受副热带高压控制、热带气旋外围下沉气流和El Niňo事件影响。  相似文献   

Measurement of biogenic sulfur emissions from soils and vegetation: Application of dynamic enclosure methods with Natusch filter and GC/FPD analysis   总被引：3，自引：0，他引：3  

B. Lamb  H. Westberg  G. Allwine  L. Bamesberger  A. Guenther 《Journal of Atmospheric Chemistry》1987,5(4):469-491

  相似文献   

闪电资料同化对河南郑州“7.20”特大暴雨预报的影响     

庞盈  胡俊俊  陈生  陆高鹏  吴翀  韦春霞  黄朝盈 《热带气象学报》2024,(1):136-145

研究了闪电资料同化对2021年7月20日河南郑州特大暴雨短临预报的影响。利用天气研究与预报（WRF）模式的三维变分（3DVAR）数据同化系统（WRFDA）,开展了两组循环同化试验：（1）同化地面和探空常规观测资料（包括风速、风向、温度和气压）的试验（CONV）;（2）同化常规观测资料和由闪电资料反演的伪相对湿度的试验（LGDA）,并与无资料同化的试验（NoDA）进行对比。结果表明,CONV的分析场和NoDA都未能模拟出强对流系统的回波结构,但由于LGDA增加了对整层大气的湿度场的调整,其分析场在闪电发生位置处的水凝物增量较大,相对湿度和反射率的分布情况与中国全球大气再分析资料（CRA）及雷达反射率观测值最接近。降水预报方面,LGDA显著提高了大暴雨雨带（6 h累积降水量≥50 mm）和强降水中心（6 h累积降水量≥200 mm）位置和强度的预报效果,对本次强降水过程的预报起到了积极作用,尤其是对前3 h的降水预报。  相似文献   

Relationship of minimum winter temperature and temperature seasonality to the northern range limit and species richness of trees in North America     

Hong QIAN  ZHANG Yangjian  Robert E.RICKLEFS  Xianli WANG 《地理学报(英文版)》2022,32(2):280-290

Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal diversity gradient.However,few studies have tested which of the two climate variables is the primary determinant.In this study,we assess whether winter coldness or temperature seasonality is more strongly associated with the northern latitudinal limits of tree species and with tree species richness in North Amedca.Tree species were recorded in each of 1198 quadrats of 110 km × 110 km in North America.We used correlation and regression analyses to assess the relationship of the latitude of the northern boundary of each species,and of species richness per quadrat,with winter coldness and temperature seasonality.Species richness was analyzed within 38 longitudinal,i.e.,north-south,bands (each being ＞1100 km long and 110 km wide).The latitudes of the north-ern range limits of tree species were three times better correlated with minimum temperatures at those latitudes than with temperature seasonality.On average,minimum temperature and temperature seasonality together explained 81.5％ of the variation in the northern range limits of the tree species examined,and minimum temperature uniquely explained six-fold (33.7％versus 5.8％) more of this variation than did temperature seasonality.Correlations of tree species richness with minimum temperatures were stronger than correlations with tempera-ture seasonality for most of the longitudinal bands analyzed.Compared to temperature sea-sonality,winter coldness is more strongly associated with species distributions at high lati-tudes,and is likely a more important driver of the latitudinal diversity gradient.  相似文献   

A data mining based approach to predict spatiotemporal changes in satellite images     

W. Boulila  I.R. Farah  K. Saheb Ettabaa  B. Solaiman  H. Ben Ghézala 《International Journal of Applied Earth Observation and Geoinformation》2011

The interpretation of remotely sensed images in a spatiotemporal context is becoming a valuable research topic. However, the constant growth of data volume in remote sensing imaging makes reaching conclusions based on collected data a challenging task. Recently, data mining appears to be a promising research field leading to several interesting discoveries in various areas such as marketing, surveillance, fraud detection and scientific discovery. By integrating data mining and image interpretation techniques, accurate and relevant information (i.e. functional relation between observed parcels and a set of informational contents) can be automatically elicited.  相似文献   

大直径高位钻孔瓦斯抽放技术在特厚煤层矿区的应用          下载免费PDF全文

段会军  郝世俊  林来彬  赵永哲  郑玉柱  胡振阳  高宗飞 《探矿工程》2013,40(12):40-42,46

针对郭家河煤矿1303工作面瓦斯涌出量大、上隅角及回风流瓦斯超限的问题,通过对高位钻孔瓦斯抽放原理及参数进行分析计算,并结合工作面生产情况,应用实践了常规高位钻孔及大直径高位钻孔瓦斯抽放技术。实践结果表明,大直径高位钻孔抽放效果远胜于常规高位钻孔,并有效地解决了瓦斯超限问题,改善了工作面的安全生产状况。  相似文献   

Characterization of halophilic C50 carotenoid-producing archaea isolated from solar saltworks in Bohai Bay,China     

隋丽英  刘良森  邓元告 《中国海洋湖沼学报》2014,32(6):1280-1287

Halophilic archaea comprise the majority of microorganisms found in hypersaline environments. C50 carotenoids accumulated in archaea cells are considered potential biotechnological products and possess a number of biological functions. Ten red colordes were isolated from brine water in a saltem crystaltizer pond of the Hangu Saltworks, China. 16S rRNA gene sequence analysis showed that the colonies belonged to the extremely halophilic archaea genera Halobacterium and Halorubrum. Two representative strains, Halobacterium strain SP-2 and Halorubrum strain SP-4, were selected for further study on the phenotypic characteristics and effects of salinity and pH on accumulation and composition of pigments in their cells. The archaeal strains were isolated and grown in a culture medium prepared by dissolving yeast extract （10 g/L） and acid-hydrolyzed casein （7.5 g/L） into brine water obtained from a I.ocal salt pond. Their optimum salinity and pH for growth were 250 and 7, respectively, although pigment accumulation （OD490/ mL broth） was highest at pH 8. In addition, at 150-300 salinity, increasing salinity resulted in decreasing pigment accumulation. Analysis of the UV-Vis spectrum, TLC and HLPC chromatograms showed that C50 carotenoid bacterioruberin is the major pigment in both strains.  相似文献   

2012年7月21日北京特大暴雨过程的水汽输送特征   总被引：6，自引：0，他引：6  

王婧羽  崔春光  王晓芳  崔文君 《气象》2014,40(2):133-145

利用NCEP再分析资料,根据水汽收支方程计算2012年7月21日北京特大暴雨时期华北东北部暴雨区域的水汽收支情况并分析水汽输送特征。得到以下结论:经向水汽输送在此次暴雨过程中起主要作用,暴雨区内水汽主要来源于中、低层(500 hPa以下)的南边界。暴雨区内水汽的辐合与暴雨发生的时间和空间具有较好一致性,在低层水汽的辐合起主要作用,中高层水汽垂直输送作用更为显著。HYSPLIT后向轨迹模拟得到的结果显示根据水汽源地划分影响此次暴雨过程水汽输送路径主要有:从孟加拉湾、南海地区处于中低层直接北上的西南路径,以及中层以下从我国东部海域(黄海、东海为主)进入内陆之后北折向东北偏北方向运动的L形高湿路径;同时高层沿着西风带西北路径的干空气输送也对此次强降水有重要影响。三者中从东部海域到达暴雨区的水汽贡献率最大,而孟加拉湾、南海的水汽输送对于此次强降水起到了明显的增强作用。  相似文献