FORGING ASIA′S GLOBAL TRANSPARK IN THE PEARL RIVER DELTA AT ZHUHAI     

Victor F S SIT 《中国地理科学(英文版)》2003,(4)

1 NEEDFORNEWCOMPETITIVENESSINTHEPEARLRIVERDELTAIn1978ChinaadoptedanewapproachofOpen andReforminitsdevelopment.Priortothis,HongKongwasaBritish-runenclaveoffreetrade,andwaslittlerelatedeconomicallywithitsnextdoorneighborandnaturalhinterland—thePearl(Zhujiang)RiverDelta(PRD)(SIT,1991).Sincethen,localinitiativesofGuangdongProvinceanditsconstituentmunicipalitieshaveprovidedanattractivemilieuforHongKongin-vestment.IthassoongrownintoHongKong'snewmanufacturingbasewhileHong…  相似文献   

VARIATIONS IN CRUSTAL THICKNESS OF THE KANE TRANSFORM IN THE NORTH ATLANTIC OCEAN     

PhilipD.Rabinowitz  胡延昌 《中国海洋湖沼学报》2001,19(4):350-360

A new approach was taken to investigate the crustal stucture of the Kane transform and its aseismic extension, using high quality bathymetry and gravity data. The gravity signatures associated with variations in crustal thickness of the transform were isolated from the observed free-air anomaly,was continued downward to the mean depth of the crust/mantle interface and converted on to the relief onthat surface. The crustal thickness of the transform was then calculated by subtracting seawater depth from the depth of the gravity-inferred crust/mantle interface. 3-D gravity investigation results indicate that the Kane transform and adjacent areas are associated with a crust thinner than normal oceanic crust. The transform trough is largely underlain by a crust less than 4.5kin thick and in the nodal basins the crust may be as thin as 3 kin. The crust beneath the fracture zone valley is 4 - 5.5 km thick. The rift valleys on the spreading segments are also characterized by thin crust (4 - 5 km thick). Thin oceanic crust extends to 20-30 km from the transform axis,except for some localized places such as the inside comerhighs adjoining the ridge-transform intersections. These gravity-inferred results match fairly well with limited published seismic results. Thinning of the crust is mainly attributable to a thin layer 3, which in turn may be explained by the combined effects of reduced magma supply at the ends of the spreading segments and tectonic activities in the region.  相似文献   

Chemical composition and its origin in spring rainwater over Taihu Lake   总被引：1，自引：0，他引：1  

王雪梅杨龙元  秦伯强纪玲玲 《中国海洋湖沼学报》2006,24(4):421-427

1 INTRODUCTION Rainfall chemical composition is mainly re- sulted from inner-cloud nucleation and under-cloud washing. The aerosol in cloud features regional scales. The concentration and chemical composition of under-cloud aerosol reflect in overall the …  相似文献   

Hydrology and related changes after harvesting native forest catchments and establishing pinus radiata plantations. Part 3. Stream temperatures     

L. K. Rowe  C. H. Taylor 《水文研究》1994,8(4):299-310

Eight small steep south-west facing catchments (1-63-8-26 ha) have been monitored in Westland, New Zealand since 1974. Two catchments were retained in native mixed evergreen forest and the rest were subjected to various harvesting and land preparation techniques before being planted with Pinus radiata between 1977 and 1980. Stream temperatures were measured in all catchments for 11 years, including up to four years before harvesting. The streamwater temperature regime under the native forest cover has a seasonal cycle, with an annual mean of about 9°C and mean daily temperatures ranging between a winter minimum of about 5.8°C and a summer maximum of 12.S°C. After harvesting, the winter minimum stream temperatures in all trials were unchanged as topography exerts the major control over incoming solar radiation. The largest rises in mean summer stream temperatures, up to 5.5°C, were in the catchments that had been clearcut and burnt before planting. The maximum stream temperature recorded was 22.8°C in a clearcut catchment with no riparian reserve. Summer stream temperatures in this catchment were up to 11°C higher than in an adjacent control catchment. Summer stream temperature rises in catchments with riparian reserves were less than 1.5°C. Seven years after harvesting, stream temperatures were dropping towards pre-treatments levels in only two of the six treated catchments as revegetation of the riparian areas occurred and the plantations became established. As these small headwater streams discharge into streams with flows one or two orders of magnitude larger, the increases in summer stream temperatures will be rapidly dissipated. However, the cumulative impact of harvesting many small headwater catchments that discharge into a larger stream could have a noticeable effect on stream temperature if intact riparian reserves were not retained in both headwater and main streams.  相似文献   

Comparison of precipitation and land runoff as sources of estuarine nitrogen     

David L. Correll  Deborah Ford 《Estuarine, Coastal and Shelf Science》1982,15(1):45-56

The seasonal and year-to-year variation of bulk precipitation as a source of total N, nitrate and ammonia is reported for a 7-year period at the Rhode River, a subestuary of Chesapeake Bay, U.S.A. These values are placed in perspective by comparison with analogous nitrogen loading due to watershed discharges.Although year-to-year variations were important, in an average year about the same amount of readily available nitrogen entered the system via precipitation as entered in land runoff and, during the summer and fall, precipitation was the largest source.  相似文献   

Hub-and-Spoke System in Air Transportation and Its Implications to Regional Economic Development——A Case Study of United States     

SONG Wei  MA Yanji 《中国地理科学(英文版)》2006,16(3)

  相似文献   

Hub-and-Spoke System in Air Transportation and Its Implications to Regional Economic Development——A Case Study of United States   总被引：1，自引：1，他引：0  

SONG Wei MA Yanji 《中国地理科学(英文版)》2006,16(3):211-216

1 Introduction Over the past twenty years since the enactment of the Airline Deregulation Act, the major US domestic carriers have developed hub-and-spoke structures for their op- erations. These have been instrumental in helping to reduce the overall costs of air travel to the U.S. public and to increase the travel options that are available. This effect also means that the quantity and quality of air ser- vices vary quite considerably between cities in the United States. The pattern of a…  相似文献   

Potential causes of differences between ground and surface air temperature warming across different ecozones in Alberta, Canada     

Jacek A. Majorowicz  Walter R. Skinner 《Global and Planetary Change》1997,15(3-4)

Analysis and modelling of temperature anomalies from 25 selected deep wells in Alberta show that the differences between GST (ground surface temperature) warming for the northern Boreal Forest ecozone and the combined Prairie Grassland ecozone and Aspen Parkland transition region to the south occur during the latter half of this century. This corresponds with recent changes in surface albedo resulting from permanent land development in the northern areas and also to increases in natural forest fires in the past 20 years. Differences between GST and SAT (surface air temperature) warming are much higher in the Boreal Forest ecozone than in the Prairie Grassland ecozone and Aspen Parkland transition region. Various hypotheses which could account for the existing differences between the GST and SAT warming in the different ecozones of Alberta, and western Canada in general, are tested. Analysis of existing data on soil temperature, hydrological piezometric surfaces, snowfall and moisture patterns, and land clearing and forest fires, indicate that large areas of Alberta, characterised by anomalous GST warming, have experienced widespread changes to the surface landscape in this century. It is postulated that this has resulted in a lower surface albedo with a subsequent increase in the absorption of solar energy. Heat flow modelling shows that, after climatic SAT warming, permanent clearing of the land is the most effective and likely cause of the observed changes in the GST warming. The greater GST warming in the Boreal Forest ecozone in the latter half of this century is related to landscape change due to land development and increasing forest fire activity. It appears to account for a portion of the observed SAT warming in this region through a positive feedback loop with the overlying air. The anthropogenic effect on regional climatic warming through 20th century land clearing and landscape alteration requires further study. In future, more accurate quantification of these various forcings will be necessary in order to distinguish between, and to detect, the variety of natural and anthropogenic influences and on climate.  相似文献   

华南区域大气成分数值模式GRACEs预报性能评估   总被引：1，自引：0，他引：1  

李婷苑  吴乃庚  邓雪娇  邓涛  陈靖扬  沈劲  邓思欣  梁华玲 《热带气象学报》2021,37(2):207-217

利用2016-2019年广东省国控站实况监测数据对华南区域大气成分数值模式系统(GRACEs)预报性能进行了综合评估。除空气质量指数AQI外,重点对PM_2.5、O₃及NO₂进行了分析评估。(1) 模式预报性能存在年际差异,对各要素的预报值总体偏低。(2) 模式预报能较好地反映空气质量的空间分布,PM_2.5中心在珠三角西北部,而O₃-8 h高值区在珠三角核心区和粤东沿海,但模式对O₃-8 h高值区存在显著预报低估现象。(3)模式可较好地模拟出PM_2.5月变化的单峰型特征和O₃-8 h月变化双峰型特征,但模式对AQI的秋冬季主峰值和春季次峰值的预报存在低估,分别与模式对O₃-8 h、PM_2.5的低估有关。(4) 模式能较好体现O₃的午后峰值和NO₂双峰值的日变化规律;模式对O₃前体物NO₂的预报偏差,有可能是导致随后几小时对O₃浓度预报偏差的重要原因。(5) 日平均浓度预报效果检验显示模式可较好预测AQI和3种污染物的变化趋势,但对夏秋季高O₃-8 h浓度预报显著偏低;模式对轻度污染及以上等级预报能力偏低,亟需提升模式对污染天气的预报能力。   相似文献   

“CMA北京模式”中三种不同阵风诊断方案在北京地区大风预报中的评估     

全继萍  李青春  仲跻芹  张舒婷  陈敏  张鑫宇  祁妙 《气象学报》2022,80(1):108-123

数值模式预报是阵风预报的重要途径之一,对“中国气象局北京快速更新循环数值预报系统（简称CMA北京模式）”中AFWA、UPP、IUM三种阵风诊断方案在北京地区大风预报中的性能进行了分析评估。两次大风过程的分析以及各季节大风预报的批量试验检验结果显示:三种方案的阵风预报存在明显差异,IUM方案的阵风预报能力优势明显。IUM方案对冷空气大风和雷暴大风预警都有较好的指示意义。其对2020年3月18日冷空气大风过程中大风起始时间、大风区位置和演变以及过程极大风速均有较好的预报效果,对2020年8月2日雷暴大风过程中大风区范围预报偏大且位置存在偏差,但对大风预警的指示意义最强。IUM方案的阵风风速预报整体偏强,但对各个季节达到或超过5级阵风的等级预报较为准确。总体而言,IUM方案对北京地区大风预报性能较好,基于该方案制作的阵风预报产品可为大风预报提供有力支撑。   相似文献