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基于LM-BP神经网络的西北地区太阳辐射时空变化研究 总被引：2，自引：1，他引：1
定量模拟太阳辐射对认识西北地区气候变化至关重要,但西北地区辐射站点稀少,而气象站点较多,利用众多的气象站点观测值模拟太阳辐射是获得太阳辐射数据很好的方法之一。利用LM (Levenberg-Marquardt) 算法对普通的BP神经网络进行优化（优化后的BP神经网络简称LM-BP神经网络）模拟太阳辐射,通过与传统气候模型模拟的太阳辐射结果对比发现,LM-BP神经网络模型的模拟精度最高,模拟值与实测值的拟合程度明显优于H-S模型和A-P模型。由此利用西北地区159个气象站点的气象数据和LM-BP神经网络模型模拟了1990~2012年这些气象站点的太阳总辐射月总量,将LM-BP神经网络模拟的气象站点的太阳辐射和25个辐射观测站的实测太阳辐射数据相结合,通过空间插值得到了西北地区太阳总辐射的空间分布,并分析了其时空分布及变化特征。研究结果发现西北地区1990~2012年的年均总辐射月总量变化为262~643 βMJ/m2,呈现“中间高,两端低”的空间分布特征。LM-BP神经网络模型的模拟精度高,是一种很有发展前景的辐射模拟方法,可将其应用在无辐射观测地区的太阳辐射模拟中。 相似文献
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现有的神经网络模拟太阳辐射的模型很少考虑云、气溶胶、水汽对太阳辐射的影响,采用MODIS提供的气溶胶、云、水汽高空大气遥感产品和常规气象数据,输入LM（Levenberg-Marquardt）算法优化后的BP（Back-Propagation）神经网络模型（简称LM-BP）模拟了和田、西宁、固原、延安4个辐射站点的太阳辐射月均值。验证结果表明：神经网络模型中加入气溶胶、云、水汽之后,4个辐射站点的
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利用2008年3月锡林浩特国家气候观象台通量观测系统获取的资料,对草原初春晴天和阴天地表能量和辐射平衡特征进行了对比。结果显示,初春典型晴天总辐射、反射辐射、向下和向上长波辐射的最大值分别为801 W·m-2、203 W·m-2、197 W·m-2和390 W·m-2;阴天总辐射与反射辐射明显减弱,峰值分别为595 W·m-2、147 W·m-2,向下、向上长波辐射最大值分别为290 W·m-2和182 W·m-2。晴天感热、潜热、土壤热通量和净辐射的日积分值分别是6.58 MJ·m-2·d-1、1.05 MJ·m-2·d-1、-0.25 MJ·m-2·d-1和5.89 MJ·m-2·d-1,阴天感热、潜热、土壤热通量和净辐射的日积分值分别是1.15 MJ·m-2·d-1、0.49 MJ·m-2·d-1、-0.08 MJ·m-2·d-1和1.65 MJ·m-2·d-1。典型晴天地表反照率早晚大,中午最小,最小值为 0.26;而阴天受云的影响,最小值仅为0.22,且日变化不明显。 相似文献
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MTCLIM模型系列研究报告(3):辐射估算方法在我国亚热带山地的有效性验证 总被引：2，自引：0，他引：2
以已有的数据、理论和模型为基础,在南方亚热带山地对MTCLIM模型的辐射估算方法进行了验证。通过研究得到以下结论:辐射子模型在该区域内模拟效果不佳。用空间外延温度估算的日总辐射的MAE普遍高于4 6MJ/m2·d-1,与实测值相关性极低。但用各自的最高温和最低温及降雨量来估计日总辐射的总MAE为3 86MJ/m2·d-1,相关系数R2在0 51～0 71间;水汽压的估算误差对辐射子模型几乎没有影响,在有水汽压驱动下所有站点的日总辐射与实测值之间的MAE为3 811MJ/m2·d-1,相关系数R2在0 55～0 73间,与不输入水汽压时的估计结果非常接近,但模型对弱辐射估计过于偏高,对强辐射估计过于偏低。 相似文献
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由于太阳辐射在山区的空间分布情况较为复杂,在Arcgis,Envi和C++基础上,提出了一个晴空条件下估算山区太阳辐射分布的模型。在借鉴国内外太阳辐射研究成果基础上充分考虑了地形因素和大气状况,利用Modtran大气辐射传输模型、DEM和Modis反照率数据建立了山区太阳辐射计算模型。以黑河上游山区为试验区,利用该模型模拟得到了黑河上游山区的太阳辐射,分析了坡度、坡向、海拔对太阳辐射空间分布的影响,并利用实测值对模型进行了验证,结果表明：该模型可较好地反映研究区内山区太阳总辐射的分布,可用于山区太阳辐射的估算。 相似文献
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川西山区太阳辐射估算及其时空分布特征 总被引：1，自引：0，他引：1
《山地学报》2017,(3)
山地地表接收的太阳入射辐射由于受到坡度、坡向及地形遮蔽等影响,导致其在时空分布上呈现较高的异质性。为定量分析山地地表太阳辐射的时空分布特征,本研究选择川西山区为研究对象,针对山地特殊地理环境,基于太阳直接辐射、散射辐射和周围地形反射辐射的参数化方案,采用Landsat系列卫星遥感影像数据和30m ASTER GDEM数据定量估算了研究区在不同时期的太阳辐射空间分布,并结合研究区的坡度、坡向、海拔等地形因子,选择夏、秋、冬不同季节对山地太阳辐射时空分布进行了综合分析。结果表明:(1)经过贡嘎山站观测数据的验证,本研究所采用的估算方案能够取得较高的估算精度,平均绝对误差为48.7 W·m-2,相对误差为6%;(2)山地太阳辐射分布具有很强的地形规律,总体特点是山脊大于山谷,阳坡大于阴坡;(3)随着坡度的增加,太阳辐射呈现递减的趋势;而随海拔的上升太阳辐射总体来说呈现增加趋势,只是在低海拔处由于地形遮蔽和山顶由于坡度陡峭造成坡面入射角小而略有回落;(4)在不同的季节,太阳辐射受地形因子的影响程度有所差异,这与太阳高度角的大小有着直接的关系。 相似文献
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《山地学报》2021,(2)
为比较和探讨中高纬度山区多种气温空间插值方法的精度及适用性,本文利用大兴安岭山脉北段及其周边区域气象站点实测气温数据,以平均绝对误差(MAE)和均方根误差(RMSE)作为评价指标对六种气温空间插值方法进行精度比较。研究结果表明:(1)反距离权重插值法(IDW)、普通克里金插值法(OK)、样条函数插值法(Spline)三种传统的气温插值方法只能粗略反映气温要素的空间分布状况,不适合气象站点稀少而地形起伏较大的区域。(2)BP神经网络(MAE:0.62℃～1.43℃,RMSE:0.84℃～2.02℃)和线性回归+残差内插的空间插值算法(MAE:0.61℃～1.55℃,RMSE:0.82℃～2.30℃)优于常规的插值方法,且BP神经网络算法能较好地反映研究区地形的高低变化以及山脉的走向。(3)在一天中的12:00—22:00时间段内,六种气温空间插值方法的插值精度与插值效果都不理想。对比六种气温空间插值方法表明,BP神经网络算法对研究区气温空间模拟效果最好,且插值效果与训练样本数量成正比。本文可为中高纬度山区气温空间化研究提供参考。 相似文献
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复杂地形下长江流域太阳总辐射的分布式模拟 总被引：1，自引：0，他引：1
利用长江流域气象站1960-2005年的观测资料(包括常规气象站点资料和辐射站点资料)、NOAA-AVHRR遥感数据(反演地表反照率),以1km×1km的数字高程模型(DEM)反映地形状况的主要数据,通过基于DEM数据的起伏地形下天文辐射模型和地形开阔度模型,分别建立了长江流域太阳直接辐射、散射辐射和地形反射辐射分布式模型,实现了长江流域太阳总辐射模拟,并对总辐射模拟结果进行了时空分布规律分析和对其受季节、纬度、地形因子(高度、坡度和坡向等)影响的局部规律分析,以及模拟结果的误差分析和站点验证分析。结果显示:太阳总辐射在季节上受影响的程度依次是春季>冬季>夏季>秋季;随着高度、坡度、纬度的增加,太阳总辐射受坡向影响的程度呈增强趋势,从坡向上看,向阳山坡(偏南坡)对太阳总辐射量明显高于背阴坡(偏北坡)。模拟的平均绝对误差为13.04177MJm-2,相对误差平均值3.655%,用站点验证方法显示:模拟绝对误差为22.667MJm-2,相对误差为4.867%。 相似文献
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取分布式模拟方法,利用福建省69个气象站1971—2007年日照资料及100 m×100 m分辨率的高程数据,计算了福建省范围内历年1—12月的太阳辐射量.结果表明,福建省年太阳总辐射主要在3 800~5 300 MJ/m2之间,年太阳直接辐射在1 800~2 800 MJ/m2之间;月太阳辐射介于230~590 MJ/m2之间,其中6—9月为一年中辐射较高的4个月份.太阳辐射的高值区主要位于福建东南部的莆田、泉州、厦门、漳州4市的沿海一带,年太阳总辐射超过4 500 MJ/m2,年太阳直接辐射超过2 100 MJ/m2.此外,受地形及地表特征的影响,位于福建北部的南平市的部分地区太阳辐射也相对较高. 相似文献
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《The Professional geographer》1988,40(4):471-499
Books reviewed in this article: USA, Eine Geographische Landeskunde , Vol. I, Der Grossraum in Strukturellem, Wandel, 3rd Ed. Helmut Blume . Introduction to Remote Sensing . James B. Campbell . The Sounds of People and Places: Readings in the Geography of American Folk and Popular Music . George O. Carney , ED. Development and Underdevelopment . John Cole . Mobility and Employment in Urban Southeast Asia: Example from Indonesia and the Philippines . Michael A. Costello , Thomas R. Leinbach , AND Richard Ulack . Soviet Asia: Economic Development and National Policy Choices . Leslie Dienes . The Third World City . David Drakakis -Smith . Scholars' Guide to Washington, DC for Cartography and Remote Sensing Imagery (maps, charts, aerial photographs, satellite images, cartographic literature and geographic information systems). Ralph E. Ehrenberg . Population and Development in the Third World . Allan AND Anne Findlay . The Early Mapping of Hawaii . Gary L. Fitzpatrick . Energetics of Physical Environment: Energetic Approaches to Physical Geography . K. J. Gregory , ED. Wildland Recreation: Ecology and Management . William E. Hammitt and David N. Cole . Agricultural Commercialization and Government Policy in Africa . J. Hinderink AND J. J. Sterkenburg . The Dynamics of American Housing . James W. Hughes AND George Sternlieb . Thailand: Buddhist Kingdom as Modern Nation State . Charles F. Keyes . Resolving Locational Conflict . Robert W. Lake , ED. Lands at Risk in the Third World: Local-level Perspectives . Peter D. Little and Michael M. Horowitz , EDS. Nathaniel Southgate Shaler and the Culture of American Science . David N. Livingstone . Regions: The Economics and Politics of Territory . Ann R. Markusen . Wetlands . William J. Mitsch and James G. Gosselink . Historical Geography: Progress and Prospect . Michael Pacione , ED. Loess and Periglacial Phenomena . Marton P$eacsi and Hugh M. French , EDS. Regional Management of Metropolitan Floodplains, Experience in the United States and Abroad . Rutherford H. Platt , ED. Human Cartography: Mapping the World of Man . Janos Szegö . Atlas of Great Lakes Indian History . Helen H. Tanner , ED. The Botany of Mangroves . P. B. Tomlinson . Urban Spatial Traffic Patterns . Rodney Vaughan . The Night After … Climatic and Biological Consequences of a Nuclear War . Yevgeni Velikhov , ED. Industrial Geography . H. D. Watts . Dictionary of Quotations in Geography . James O. Wheeler and Francis M. Sibley . Vermont Townscape . Norman Wiliams , Jr. , Edmund K. Kellogg and Peter M. Lavigne . 相似文献
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P. Guilizzoni A. Marchetto A. Lami N. G. Cameron P. G. Appleby N. L. Rose Ø. A. Schnell C. A. Belis A. Giorgis L. Guzzi 《Journal of Paleolimnology》1996,15(3):245-264
A palaeoecological study of an oligotrophic alpine lake, Paione Superiore (Italy), provided a record of historical changes in water quality. Historical trends in lake acidification were reconstructed by means of calibration and regression equations from diatoms, chrysophycean scales and pigment ratios. The historical pH was inferred by using two different diatom calibration data sets, one specific to the alpine region. These pH trends, together with the record of sedimentary carbonaceous particles and chironomid remains, indicate a recent acidification of this low alkalinity lake.Concentration of total organic matter, organic carbon, nitrogen, biogenic silica (BSiO2), chlorophyll derivatives (CD), fucoxanthin, diatom cell concentration and number of chironomid head capsules increased during the last 2–3 decades. When expressed as accumulation rates, most of these parameters tended to decrease from the past century to c. 1950, then all except P increased to the present day. A marked increase in sedimentary nitrogen may be related to atmospheric pollution and to the general increases in output of N in Europe. High C/N ratios indicate a prevailing allochthonous source of organic matter.Finally, the increase in measured air temperature from the mid-1800's appeared to be related to lake water pH before industrialization: cold periods generally led to lower pH and vice-versa. The more recent phenomenon of anthropogenic acidification has apparently decoupled this climatic-water chemistry relationship. 相似文献
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K. F. Walker I. G. Dunn D. Edwards T. Petr H. Z. Yang 《International Journal of Salt Lake Research》1995,4(3):169-222
Quinghai Hu is a large, high-altitude, saline lake in north-western China, and supports a fishery based on an endemic species of naked carp (snow trout). The fish take seven years to attain maturity and a marketable weight of 300 g, and have a lifespan of 14–21 years under the present fishery regime. They seasonally migrate from the lake to spawn over the gravel beds of inflowing rivers, but these areas have been reduced by weirs and irrigation diversions and recruitment may have declined. The population may have been affected also by a 1.85-m fall in the lake level over the past 30 years, and by associated changes in salinity. The fishery was opened to large-scale exploitation in 1958. Yields declined sharply (max. 28,523 tonnes, 1960) as the larger, older fish were removed, and then more slowly (min. 2523 tonnes, 1983). Since 1987 the fish factory has been limited to an annual quota of 1200 tonnes, taken by a fleet of four pair trawlers. Another 800 tonnes are taken by licensed fishermen, mainly using gill nets, and perhaps 1000 tonnes are taken illegally. The estimated total catch in 1992 was 3000 tonnes. New trawlers introduced in 1989–90 substantially increased the factory's catch per unit effort, and in 1990 the quota was virtually filled in one month in a zone within 20 km of the factory. Although this could suggest that the stocks will be conserved if the quota is retained, at least half of the catch in 1989–92 consisted of immature individuals. Trawling operations recently were suspended following a further decline in the catch after 1992. While the new trawlers are capable of a major increase in effort, neither the changing environment, the fish stocks or the present markets favour intensified pressure. Gillnets may provide better control over the minimum size limit and may cause less damage than trawling. Other options to improve the viability and profitability of the fishery include improvements in handling, processing and marketing. Failure to develop the fishery may encourage attempts to introduce exotic fish, at some risk to survival of the local species. 相似文献
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Chironomidae (Diptera) remains in surficial lake sediments from the Canadian Cordillera: analysis of the fauna across an altitudinal gradient 总被引：3，自引：0，他引：3
The altitudinal distribution of Chironomidae (Diptera) in the southern Canadian Cordillera was analyzed by means of head capsules preserved in surficial sediments of 30 lakes. Taxa characteristic of late-glacial deposits of southern, coastal British Columbia are extant at high elevations, particularly in the Rocky Mountains, and in large, deep, low-elevation lakes. Many chironomid taxa common at low elevations in the southern Canadian Cordillera were not found in alpine and upper subalpine lakes. These faunal differences are probably climatically related. The differences in fauna between high and low-elevation lakes parallel differences between arctic and temperate lakes. 相似文献
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MATT K. MATSUDA 《Geographical review》2007,97(2):230-243
ABSTRACT. Narratives concerning Pacific Ocean territories are often historically derived from European and American mainland visions of great, empty oceans dotted with deserted and uninhabited islands. However, research by indigenous and outlander scholars, along with struggles for political and cultural autonomy in the Pacific, has brought attention to vital island communities and 6has raised questions about a Pacific‐island way of understanding the world. This understanding is traced through scholarly and artistic engagements with history, island‐community studies, and navigational philosophies and is framed by a growing theoretical literature on epistemologies of place from the disciplines of geography and oceanography. 相似文献
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Precipitation is an important component of global water and energy transport and a major aspect of climate change. Due to the scarcity of meteorological observations, the precipitation climate over Tibet has been insufficiently documented. In this study, the distribution of precipitation during the rainy season over Tibet from 1980 to 2013 is described on monthly to annual time scales with meteorological observations. Furthermore, four precipitation products are compared to observations over Tibet. These datasets include products derived from the Asian Precipitation-Highly-Resolved Observational Data(APHRO), the Global Precipitation Climatology Centre(GPCC), the University of Delaware(UDel), and the China Meteorological Administration(CMA). The error, relative error, standard deviation, root-mean-square error, correlations and trends between these products for the same period are analyzed with in situ precipitation during the rainy season from May to September. The results indicate that these datasets can broadly capture the temporal and spatial precipitation distribution over Tibet. The precipitation gradually increases from northwest to southeast. The spatial precipitation in GPCC and CMA are similar and positively correlated to observations. Areas with the largest deviations are located in southwestern Tibet along the Himalayas. The APHRO product underestimates, while the UDel, GPCC, and CMA datasets overestimates precipitation on the basis of monthly and inter-annual variation. The biases in GPCC and CMA are smaller than those in APHRO and UDel with a mean relative error lower than 10% during the same periods. The linear trend of precipitation indicates that the increase in precipitation has accelerated extensively during the last 30 years in most regions of Tibet. The CMA generally achieves the best performance of these four precipitation products. Data uncertainty in Tibet might be caused by the low density of stations, complex topography between the grid points and stations, and the interpolation methods, which can also produce an obvious difference between the gridded data and observations. 相似文献
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Jean-Claude Plaziat 《Journal of Paleolimnology》1993,8(2):163-169
Potamids generally live in estuaries, lagoons, and along protected sea shores. However, their ability to colonize intracontinental lakes has been underestimated due to non- or misidentifications. Potamides conicus, the only present lacustrine Potamid currently found in North Africa, belongs to a lagoon-type (thalassoid) malacofauna, dominated by the Cardium Cerastoderma glaucum: this fauna occurs in association with Foraminifera (especially Ammonia beccarii) and Ostracoda (Cyprideis gr. Torosa). Potamids have been found 250 to 900 km from the nearest sea shore: passive dispersal (probably through birds) is the primary dispersal mechanism. Shell morphology and ornamentation can be used to characterize life environment (lacustrine versus marine) but not distance from sea shore. The presence of Potamid-Foraminifera fauna in the fossil record has been interpreted as providing evidence for a sea connection (e.g., gulfs, lagoons). However, more recent paleoecological studies have demonstrated that such assemblages span an ecological gradient from freshwater to hypersaline lacustrine environments. Thus, the occurrence of modern Potamids in lacustrine (in addition to maritime) environments has important implications for Quaternary and Tertiary paleogeographic investigations. Lacustrine Potamids have been recorded from the European Tertiary (France, Spain) and from the Sahara Holocene. More research is required for the better understanding of the distribution and ecology of Potamids in modern and fossil lakes of other continents.This publication is the fifth of a series of papers presented at the Conference on Sedimentary and Paleolimnological Records of Saline Lakes. This Conference was held August 13–16, 1991 at the University of Saskatchewan, Saskatoon, Canada. Dr Evans is serving as Guest Editor. 相似文献