Simulation of the annual and diurnal cycles of rainfall over South Africa by a regional climate model     

Benjamin Pohl  Mathieu Rouault  Shouraseni Sen Roy 《Climate Dynamics》2014,43(7-8):2207-2226

The capability of a current state-of-the-art regional climate model for simulating the diurnal and annual cycles of rainfall over a complex subtropical region is documented here. Hourly rainfall is simulated over Southern Africa for 1998–2006 by the non-hydrostatic model weather research and forecasting (WRF), and compared to a network of 103 stations covering South Africa. We used five simulations, four of which consist of different parameterizations for atmospheric convection at a 0.5 × 0.5° resolution, performed to test the physic-dependency of the results. The fifth experiment uses explicit convection over tropical South Africa at a 1/30° resolution. WRF simulates realistic mean rainfall fields, albeit wet biases over tropical Africa. The model mean biases are strongly modulated by the convective scheme used for the simulations. The annual cycle of rainfall is well simulated over South Africa, mostly influenced by tropical summer rainfall except in the Western Cape region experiencing winter rainfall. The diurnal cycle shows a timing bias, with atmospheric convection occurring too early in the afternoon, and causing too abundant rainfall. This result, particularly true in summer over the northeastern part of the country, is weakly physic-dependent. Cloud-resolving simulations do not clearly reduce the diurnal cycle biases. In the end, the rainfall overestimations appear to be mostly imputable to the afternoon hours of the austral summer rainy season, i.e., the periods during which convective activity is intense over the region.  相似文献   

Lithospheric structure below transantarctic mountain using receiver function analysis of TAMSEIS data   总被引：1，自引：0，他引：1  

P. Kumar  Karabi Talukdar  Mrinal K. Sen 《Journal of the Geological Society of India》2014,83(5):483-492

The lithospheric structure of Antarctica has been investigated from P- (PRF) and S- receiver functions (SRF) using the seismological data from Trans-Antarctic Mountain Seismic Experiment (TAMSEIS). For the stations deployed on the thick ice sheet, estimation of crustal parameters from PRF may be erroneous as the Moho conversions may interfere with the reverberations within the thick ice sheet. However, the free surface multiples are well observed in PRF. On the other hand, in SRFs, the primary conversions of interest and multiples are separated by the mother S-phase. Therefore, it is advantageous to interpret PRF and SRF jointly for the regions where we have thick low velocity layer at the top such as ice or sediments. The crustal structure and corresponding parameters have already been estimated by various workers, but here we interpret the PRF and SRF jointly to minimize the ambiguity and map the lithospheric architecture below TAM. Our analysis reveals that the average crustal thickness beneath the east Antarctica craton is ～44 km with Vp/Vs ranging between ～1.7 and 1.9. Below Trans-Antarctic Mountain (TAM), the average crustal thickness is ～36 km with higher Vp/Vs of ～1.8–2.0. The rift and the volcanic affected coastal region show erratic depths and Vp/Vs, primarily due to the absence of either primary conversion or multiples in the receiver functions. A small number of stations far from the volcano show that the crust is thinnest (～26 to 34 km thick) in the coastal part. The contribution of this study is the mapping of the lithospheric configuration, not done so far using SRF. The SRF section along a profile spanning E-, W- Antarctica and TAM reveals that the lithospheric thickness in the coast is ～80 km and below TAM it is ～120 km. In the central thick ice cover region, the lithosphere thickens upto ～150 km towards Vostok highlands. The most intriguing feature in our SRF section is that the crust and lithosphere are shallow below TAM compared to the E- Antarctica. Further, we observe a mid-lithospheric low velocity layer confined mostly below TAM, suggesting that the thermal buoyancy could be the prime cause for the upliftment of TAM.  相似文献   

Shell microstructure of late Cretaceous (Maastrichtian) oysters from Ariyalur,Tamil Nadu     

Anand K. Jaitly  Sanjay K. Mishra  Shrinjana Sen 《Journal of the Geological Society of India》2014,84(1):41-54

The micro-morphological shell characters (both in optical microscope and SEM) have been used to discriminate in between oyster’s sub-families Pycnodonteinae Stenzel 1959, Exogyrinae Vyalov 1936, Ostreinae Refinesque 1815 and Lophinae Vyalov 1936. These sub-families are represented by six constituent genera Phygraea (Phygarea) vesicularis (Lamarck 1806), Hyotissa semiplana (Sowerby1813), Curvostrea rouvellei (Coquand 1862), Ceratostreon pliciferum (Dujardin 1837), Agerostrea ungulata (Schlotheim 1813) and Rastellum (Arctostrea) pectinatum (Lamarck 1810) in the late Cretaceous (Maastrichtian) sediments of the Ariyalur area of Tamil Nadu, south India. The optical microscopic observations and SEM studies of the shells of these six genera clearly indicate that all the four sub-families consist of distinctive set of shell-microstructures. Sub-family Pycnodonteinae is characterized by predominance of vesicular, exogyrinae by prismatic, Ostreinae by cross foliated and Lophinae by foliated shell microstructures. Besides their characteristic shell microstructures, some additional microstructures are also visible in the shells of some of the genera of these four sub-families.  相似文献   

湖南禾库地区水系沉积物地球化学特征及找矿预测   总被引：5，自引：3，他引：2       下载免费PDF全文

赵武强 崔森邹先武  汤朝阳夏杰 金世超 《中国地质》2014,41(2):638-647

依据1∶5万水系沉积物测量资料,分析研究了湖南禾库地区水系沉积物地球化学特征。对元素分布、单元素异常、元素相关性、异常元素组合等特征的研究表明水系沉积物地球化学测量方法在高山峻岭、地形复杂的禾库地区有良好的找矿效果,并优选了嗅脑和杉木冲2处铅锌找矿远景区。  相似文献   

全球过去千年典型暖期温度空间格局重建   总被引：1，自引：0，他引：1  

史锋  杨保  赵森  杨凤梅 《第四纪研究》2014,34(6)

利用过去两千年全球变化研究网络(PAGES 2k network)最新公布的501条代用记录,重建了全球过去千年全年平均温度空间格局的演化特征,对比分析了中世纪暖期及其最暖100年与20世纪现代暖期、中世纪暖期和小冰期最暖30年与20世纪最近30年的年平均温度空间模态异同.结果显示,在世纪尺度上,现代暖期与历史上中世纪暖期的温度异常空间格局大致相同,变化幅度也在大部分区域相当,但从年代际尺度上,最近30年的升温比过去千年中世纪暖期和小冰期两个典型时期都明显.值得一提的是北大西洋中高纬度海温变化与上述特征并不相同,在年代际和世纪尺度上小冰期和中世纪暖期海温均高于20世纪.可能原因是大西洋经圈翻转环流在中世纪暖期、小冰期和20世纪现代暖期等3个特征时段对太阳辐射、火山活动和温室气体等外强迫的响应不同.  相似文献   

陆海统筹视域下国土空间多维冲突识别与分区调控——以莱州市为例     

李建春  高玉婷  曲衍波  关梅  张勇  王森 《地理科学》2022,42(7):1155-1165

充分识别陆海空间冲突并制定科学规划是实现陆海统筹的关键。基于陆海空间利用现状与规划,构建陆海空间冲突的理论分析框架,采用冲突识别矩阵、邻域冲突测度模型和社会网络分析等方法,以山东省莱州市为案例区,1 km格网为研究单元,分别从陆地对海洋、海洋对陆地2个方向定量识别陆海空间的现状冲突和规划冲突,并结合四象限模型对冲突进行分区。主要研究结果如下：① 从冲突范围与强度来看,莱州市陆地利用与规划越过海岸线的范围更大,陆海交互冲突范围将持续增加,陆海统筹应重视空间复合利用与跨系统交互影响。② 从冲突的类型来看,现状冲突中陆地的水域与湿地以及海洋的渔业用海等利用方式对海陆系统产生的影响较大;而在规划冲突中,陆地的一般农地区和其他用地区,海洋的农渔业区和港口航运区4类功能分区跨系统产生的影响较大。③ 现状与规划的耦合分区结果显示,相对独立的陆海空间规划对于控制和缓解空间冲突具有一定效果,然而陆海空间统筹利用与管理迫在眉睫,应结合系统观点根据不同分区特点进行优化。  相似文献   

Derivations of coupled equations appropriate to the lower regions of the ionosphere     

S. S. De  B. K. Sarkar  Bithika Ghosh  Manasi Mal  B. Ghosh  S. Bandyopadhyay  S. K. Adhikari  A. C. Sen 《Astrophysics and Space Science》1991,184(2):281-285

Coupled equations are derived for different ionospheric parameters through susceptibility dyadic appropriate to the medium. The nature of dispersion within the medium is studied.  相似文献   

北京市地理国情监测外业调查与核查技术探讨     

杨旭东  杨伯钢  刘博文  李森  王淼 《北京测绘》2018,32(5):532-535

外业调查与核查是获取地理国情信息的重要手段,可帮助内业解译,更好地完成工作。本文介绍了北京市地理国情监测外业调查与核查工作的具体内容,从北京市实际需求出发,研究制定了一套面向北京市的地理国情监测外业调查与核查的技术方案,保证了北京市国家基础性监测和市情专题性监测的合理有效开展,为今后地理国情常态化监测外业工作的实施提供一定的技术参考。  相似文献   

页岩气地质调查井小口径绳索取心钻探技术分析          下载免费PDF全文

张强  战启帅  张文良  赵东生  李森 《探矿工程》2022,49(5):72-79

小口径绳索取心钻探技术在页岩气地质调查井中具有不可替代的优势,同时也存在较大的局限性。结合小口径绳索取心工艺在10余口页岩气调查井的应用情况,从地质条件、技术要求、设备及配套机具等方面归纳总结了施工中的难点,从井身结构、设备配置、取心工艺、泥浆体系、复杂情况预防等方面提出了优化方案。依据优化后的施工技术措施,在后续施工的页岩气调查井中取得了良好的效果,岩心采取率保持在97%以上,台月进尺超过了400 m,复杂发生频次控制在2次以下。对下一步小口径页岩气调查井施工具有一定的借鉴意义。  相似文献   

Wildfire impacts on education and healthcare: Paradise,California, after the Camp Fire     

Hamideh  Sara  Sen  Payel  Fischer  Erica 《Natural Hazards》2022,111(1):353-387

Natural Hazards - The 2018 Camp Fire caused significant damages to the education and healthcare systems in the town of Paradise, CA. This paper presents the findings of a qualitative case study...  相似文献