起伏地形下天文辐射分布式估算模型

基于数字高程模型（DEM）,建立了起伏地形下天文辐射分布式估算模型.模型全面考虑了地形因子对天文辐射的影响,只需DEM数据作为输入项,适用于遥感图像处理、地理信息系统等数据处理平台.以1km×1km分辨率的DEM数据作为地形的综合反映,计算了我国全年各月天文辐射的空间分布.结果表明：我国年天文辐射总量有明显的纬向分布特点,随着纬度的降低,年天文辐射总量由北向南增加;由于受坡向、坡度和地形遮蔽因子影响,山区天文辐射表现出非地带性分布特征.本文所提供的我国天文辐射数据产品,可作为基础地理数据供相关研究应用.     

复杂地形下黄河流域月平均气温分布式模拟

通过对常规气象站月平均气温资料的分析,发现在影响气温的众多因素中,海拔高度、太阳总辐射、地表长波有效辐射对气温具有显著影响.建立了月平均气温的物理经验统计模型,结合复杂地形下太阳总辐射分布式模拟结果,提出了依托常规地面气象观测资料实现复杂地形下月平均气温分布式模拟的方法,生成了黄河流域1km×1km分辨率月平均气温、月平均最高气温、月平均最低气温的空间分布图.分析表明,模拟结果能较好地反映气温的宏观分布趋势和局地分布特征.交叉验证结果表明,模型具有很好的稳定性,各月平均气温、月平均最高气温、月平均最低气温的模拟误差平均为0.19~0.35℃;加密站验证和个例年验证表明,模型具有良好的空间维和时间维模拟能力.提出的月平均气温分布式模型立足于常规地面气象观测资料,不依赖于山地野外考察资料,可以方便地在广大地区推广应用.     

复杂地形下黄河流域月平均气温分布式模拟

通过对常规气象站月平均气温资料的分析,发现在影响气温的众多因素中,海拔高度、太阳总辐射、地表长波有效辐射对气温具有显著影响．建立了月平均气温的物理经验统计模型,结合复杂地形下太阳总辐射分布式模拟结果,提出了依托常规地面气象观测资料实现复杂地形下月平均气温分布式模拟的方法,生成了黄河流域1km×lkm分辨率月平均气温、月平均最高气温、月平均最低气温的空间分布图．分析表明,模拟结果能较好地反映气温的宏观分布趋势和局地分布特征．交叉验证结果表明,模型具有很好的稳定性,各月平均气温、月平均最高气温、月平均最低气温的模拟误差平均为0．19～0．35℃;加密站验证和个例年验证表明,模型具有良好的空间维和时间维模拟能力．提出的月平均气温分布式模型立足于常规地面气象观测资料,不依赖于山地野外考察资料,可以方便地在广大地区推广应用．     

考虑关断时间的地面瞬变电磁三维带地形反演

起伏地形和关断时间对地面瞬变电磁响应影响严重,这给传统基于水平地表模型和理论阶跃波形的瞬变电磁数据解释技术带来很大困难.为此,本文开展考虑起伏地形和关断时间的地面瞬变电磁三维反演算法研究.正演采用基于非结构网格和后退欧拉隐式时间离散格式的时间域有限元算法,快速模拟起伏地表模型瞬变电磁响应.反演采用L-BFGS算法,减少每次反演迭代的计算量.针对发射线圈随地表起伏变化的特点,利用基于偶极子离散的场源处理技术模拟发射源的实际形状,采用瞬时电流脉冲技术实现考虑关断时间的地面瞬变电磁三维正演模拟.我们首先将本文开发的三维反演算法应用于理论模型的反演计算中,检验本文算法的可靠性,并分析地形和关断时间对反演结果的影响特征.在此基础上,进一步将本文算法应用于实测数据反演,验证本文算法的实用性.     

全球陆表湿地潜在分布区制图及遥感验证

由于城市化和农业垦殖等人类活动不断增强,很多湿地生态系统受到侵占或干扰.保护湿地资源需要准确的湿地分布.然而由于湿地类型复杂多样,地面调查困难,大范围湿地分布制图很难完成.目前还没有专门用于湿地保护和规划且有较高分辨率的全球湿地分布数据.采用水文、气候数据结合1 km分辨率的混合地形指数(CTI)数据,利用陆表湿地和地下水位的关系,模拟出不考虑人类活动影响状况下30 s分辨率的全球陆表湿地潜在分布区.这是最高分辨率的全球陆表湿地的潜在分布数据.模拟结果显示全球陆表湿地潜在分布区面积达到3.316×107 km2.用遥感获得的实际湿地数据对陆表湿地模拟结果进行精度验证,总体精度达到83.7%.本次模拟结果可以作为构建全球湿地实际分布数据库的基础.由于模拟过程未考虑农业灌溉、建坝等人类活动对湿地的干扰破坏,因此本文对陆表湿地潜在分布区的模拟结果大于当前几种全球土地覆盖制图产品中湿地的面积.本文采用方法所需数据相对较少,精度高于其他产品.     

嫦娥一号激光测距数据及全月球DEM模型

激光高度计是搭载在CE-1上的主要载荷之一, 用于月球表面的地形测量. 2007年11月28日02点22分, 激光高度计成功获得第一个探测数据, 截止到2008年12月4日, 总共获取了约912万个探测数据, 数据覆盖全月面. 我们利用这些探测数据制作了空间分辨率为3 km的全月DEM模型, 月表地形地貌特征反映明显, 地形细节表达层次分明、清晰可辨. DEM模型的平面定位精度为445 m (1σ), 高程测量精度为60 m (1σ). 根据这一DEM模型, 测得月球表面最大高差为19.807 km, 最高点位于Engel’gardt撞击坑东缘(158.656°W, 5.441°N, +10.629 km), 最低点位于Antoniadi撞击坑底部(172.413°W, 70.368°S, -9.178 km). 通过比较, CE-1的激光高度计DEM模型, 在精度和分辨率上明显优于美国ULCN2005, 与日本SELENE激光高度计DEM模型相当, 测量到的最高点与SELEN结果相似, 但CE-1数据新发现了比SELEN结果更低的最低点.     

地形起伏对基于地震波形的浅源地震深度反演影响——以2017年9月3日朝鲜M6.3事件为例

震源深度是核试验以及塌陷等浅源地震研究中的关键参数,可以为事件成因分析提供关键信息.然而朝鲜核试验区域地形起伏较大,地形效应可能对震源深度反演的结果造成影响.本文基于理论地震图进行测试,研究了地形起伏对震源深度反演的影响.发现震源深度小于2km时,不考虑地形影响,反演得到的震源深度会系统偏浅0.2km左右.然后利用MDJ2速度结构模型,我们反演了2017年9月3日朝鲜M6.3事件的震源参数,结果显示震源深度约为0.8km.进一步基于带地形的格林函数重新反演了该事件的震源深度,发现在1km处波形拟合结果较好.不同速度模型测试结果显示该事件的震源深度反演误差约为1km.案例研究表明,基于层状均匀速度模型,利用区域地震波形资料反演的震源深度可以为浅源事件成因分析提供关键约束.     

基于CryoSat-2测高数据的全南极冰盖DEM的建立与精度评估

数字高程模型(DEM)是南极冰盖变化研究的基础,由于现场实测数据的稀缺,卫星测高数据是南极地区构建DEM的'主要数据来源.CryoSat-2是新一代用于极地冰盖、海冰监测的测高卫星,本文利用2012-12-2015-01两个完整周期的CryoSat-2测高数据建立一个新的南极冰盖DEM.坡度是影响卫星测高精度的重要因素之一,利用改进的重定位方法对CryoSat-2数据进行坡度改正.插值方法是影响DEM精度的重要因素,通过对几种常用插值方法的比较,最后选用克里金插值方法对测高数据进行插值,建立了1km分辨率的南极DEM.在88°S以南的CryoSat-2数据空白区,利用南极数字数据库(ADD)的等高线数据对DEM进行填补,建立了全南极冰盖DEM.利用ICESat卫星测高数据、IceBridge航空测高数据以及GPS地面实测数据对新建立的CryoSat-2 DEM进行精度验证,并与Bamber 1 km DEM、ICESat DEM、RAMPv2 DEM以及JLB97 DEM等四种国际上常用的南极DEM进行比较.结果表明:新建立的CryoSat-2 DEM的整体精度约为0.730±8.398 m;在冰弯顶部区域,DEM精度优于1 m;在冰架上,DEM精度约为4 m;在内陆冰盖大部分地区,DEM精度优于10 m;在地形复杂的山区和沿海边缘地区,DEM误差超过150 m.     

三维起伏地形条件下航空瞬变电磁响应特征研究

航空瞬变电磁法以其速度快、成本低、通行性好等的优势能够有效的应用于地质地形条件复杂的地区.目前对于航空瞬变电磁法的研究主要基于平坦地形的理想情况,对于地形效应的研究相对较少,然而实际应用中地形不可避免,若忽略地形影响将对资料解释造成较大的误差,从而制约航空电磁方法的进一步发展.本文基于交错网格的时域有限差分方法对三维起伏地形条件下航空瞬变电磁进行正演模拟,在保证算法准确性的前提下给出大量模型算例.以经典地形模型为例,利用所给方法计算三维正演响应,结果显示起伏对于航空瞬变电磁数据有着显著的影响且影响主要集中在早期.而后,以实际地质资料为基础,构建起伏地形条件下包含多个异常体的三维复杂模型,计算了复杂模型的航空瞬变电磁响应,并给出三维全域视电阻率曲线,从而对地形效应的影响有了更加直观的认知.最后,通过大量模型讨论了地形的尺寸参数、电性参数、飞行轨迹与飞行高度等因素变化对于航空瞬变电磁数据的影响情况,并得出有价值的结论.     

基于决策树考虑地形特征的场地参数估计方法

发展基于地形特征的场地参数VS30估计方法因其具有重要应用需求而成为研究热点.以我国新疆维吾尔自治区和河北省的DEM数据和工程钻孔资料验证了基于决策树理论考虑地形特征的VS30估计方法在我国的适用性,检验方法的准确性和对DEM数据精度的敏感性.得到如下结论:(1)基于决策树理论考虑地形坡度、表面纹理和局部凸度划分了两个...     

Distributed modeling of monthly air temperatures over the rugged terrain of the Yellow River Basin

Our analyses of the monthly mean air temperature of meteorological stations show that altitude, global solar radiation and surface effective radiation have a significant impact on air temperature. We set up a physically-based empirical model for monthly air temperature simulation. Combined the proposed model with the distributed modeling results of global solar radiation and routine meteorological observation data, we also developed a method for the distributed simulation of monthly air temperatures over rugged terrain. Spatial distribution maps are generated at a resolution of 1 km×1 km for the monthly mean, the monthly mean maximum and the monthly mean minimum air temperatures for the Yellow River Basin. Analysis shows that the simulation results reflect to a considerable extent the macro and local distribution characteristics of air temperature. Cross-validation shows that the proposed model displays good stability with mean absolute bias errors of 0.19°C–0.35°C. Tests carried out on local meteorological station data and case year data show that the model has good spatial and temporal simulation capacity. The proposed model solely uses routine meteorological data and can be applied easily to other regions. Supported by China Meteorological Administration key Project on New Technique Diffusion (Grant No. CMATG2006Z10) and Jiangsu Key Laboratory of Meteorological Disasters (Grant No. KLME050102)     

Modeling the land surface reflectance for optical remote sensing data in rugged terrain

A model for topographic correction and land surface reflectance estimation for optical remote sensing data in rugged terrian is presented.Considering a directional-directional reflectance that is used for direct solar irradiance correction and a hemispheric-directional reflectance that is used for atmospheric diffuse irradiance and terrain background reflected irradiance correction respectively,the directional reflectance-based model for topographic effects removing and land surface reflectance calculation is developed by deducing the directional reflectance with topographic effects and using a radiative transfer model.A canopy reflectance simulated by GOMS model and Landsat/TM raw data covering Jiangxi rugged area were taken to validate the performance of the model presented in the paper.The validation results show that the model presented here has a remarkable ability to correct topography and estimate land surface reflectance and also provides a technique method for sequently quantitative remote sensing application in terrain area.     

Heli-borne gravity gradiometry in rugged terrain

For airborne gravity gradiometry in rugged terrain, helicopters offer a significant advantage over fixed-wing aircraft: their ability to maintain much lower ground clearances. Crucially, this provides both better signal-to-noise and better spatial resolution than is possible with a fixed-wing survey in the same terrain. Comparing surveys over gentle terrain at Margaret Lake, Canada, and over rugged terrain at Mount Aso, Japan, demonstrates that there is some loss of spatial resolution in the more rugged terrain. The slightly higher altitudes forced by rugged terrain make the requirements for terrain correction easier than for gentle terrain. Transforming the curvature gradients measured by the Falcon gravity gradiometer into gravity and the complete set of tensor components is done by a Fourier method over gentle terrain and an equivalent source method for rugged terrain. The Fourier method is perfectly stable and uses iterative padding to improve the accuracy of the longer wavelengths. The equivalent source method relies on a smooth model inversion, and the source distribution must be designed to suit the survey design.     

Atmospheric Broadband Model for Computation of Solar Radiation at the Earth’s Surface. Application to Mediterranean Climate

—This paper deals with a new broadband atmospheric model designed for predicting the total and diffuse solar radiation incident on the earth’s surface in medium or large-sized coastal or near-coastal cities, under a clear or cloudy sky. The revised solar spectrum is used. The atmospheric transmittance of each atmospheric parameter contributing to solar radiation depletion, water vapor, ozone, uniformly mixed gases, molecules and aerosols, is calculated using parameterized expressions resulting from integrated spectral transmittance functions. The beam and diffuse radiation components are obtained as a function of the specific atmospheric transmittances. The model requires the following parameters as inputs: total water vapor and ozone amount in a vertical column, sunshine duration and the surface albedo. The model has been used for validation purposes at two stations with slightly different characteristics (NOA and Penteli) in the Athens basin, where total and diffuse radiation measurements are available, for a period of 34 months for NOA and 23 for Penteli. The NOA station is located on a small hill (107 m a.m.s.l.) near the center of Athens, while the Penteli station (500 m a.m.s.l.) is situated in a relatively less polluted area in northern Athens. The clear sky part of the model was tested for 70 individual “clear” days with 2-minute intervals, while the whole model was checked with monthly “mean” days and mean hourly values. A close agreement between the calculated and the measured values of total and diffuse solar radiation is observed.     

Diffuse solar radiation and associated meteorological parameters in India

Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another.     

Topography-adjusted solar radiation indices and their importance in hydrology

Abstract

Solar radiation, direct and diffuse, is affected by surface characteristics, such as slope, aspect, altitude and shading. The paper examines the effects of topography on radiation, at multiple spatiotemporal scales, using suitable geometric methods for the direct and diffuse components. Two indices are introduced for comparing the direct radiation received by areas at the same and different latitudes. To investigate the profile of direct radiation across the whole of Greece, these are evaluated from an hourly to annual basis, via GIS techniques. Moreover, different approaches are examined for estimating the actual global radiation at operational spatial scales (sub-basin and terrain), according to the available meteorological data. The study indicates that the errors of typical hydrometeorological modelling formulas, which ignore the topographic effects and the seasonal allocation of direct and diffuse radiation, depend on the spatial scale and are non-uniformly distributed in time. In all cases, the estimations are improved by applying the proposed adjustment approaches. In particular, the adjustment of the measured global radiation ensures up to 10% increase of efficiency, while the modified Angström formula achieves slight (i.e. 2–4%) increase of efficiency and notable reduction of bias.

Editor Z.W. Kundzewicz

Citation Mamassis, N., Efstratiadis, A. and Apostolidou, I.-G., 2012. Topography-adjusted solar radiation indices and their importance in hydrology. Hydrological Sciences Journal, 57 (4), 756–775.     

太阳辐射和地面气象要素的日环食效应

本文通过对1987年9月23日日环食期间太阳辐射和地面气象要素等实测资料的分析,指出了在日环食过程中太阳辐射和地面气象要素等的变化,也叙述了日食期间地面臭氧含量的变化;第一次在国内测得了由日食引起的大气重力波,进而讨论了大气重力波的若干特性.     

Numerical modelling of spectral sky radiance during a total solar eclipse

Ground-based observations of the spectral sky radiance within the totality region during a total solar eclipse are of significant interest because the contribution from direct and single scattered light from the solar disk is eliminated. In the present paper, we develop a numerical model of the spectral sky radiance during totality, evaluate the contribution of double scattered sunlight to the sky radiance at totality and compare it to solar corona emissions. The results show that the single scattered coronal light is the major contaminant in ground-based observations of the corona, opposite to what was believed before. For observation directions outside the corona the double scattered sun radiation dominates over the single scattered coronal light.     

Data‐driven modelling of shortwave radiation transfer to snow through boreal birch and conifer canopies

Hydrological and land surface models require simple but accurate methods to predict the solar radiation transmitted through vegetation to snow, backed up by direct comparisons to data. Twenty shortwave pyranometers were deployed in forest plots of varying canopy structures and densities in sparse birch forest near Abisko, Sweden, in spring 2011 and mixed conifer forest near Sodankylä, Finland, in spring 2012. Above‐canopy global and diffuse shortwave irradiances were also measured. These data were used to test a model that uses hemispherical photographs to explicitly estimate both diffuse radiation and direct beam transmission, as well as two models that apply bulk canopy parameters and versions of Beers Law. All three models predict canopy shortwave transmission similarly well for leafless birch forest, but for conifers, the bulk methods perform poorly. In addition, an existing model of multiple reflections between canopy and snow was found to be suitable for birch, but not conifers. A new bulk approach based on empirical relationships with hemisphere‐averaged sky view fraction showed improved performance for both sites; this suggests benefits of avoiding the use of plant area index calculated from optical methods, which can introduce errors. Furthermore, tests using common empirical diffuse radiation models were shown to underestimate shortwave transmission by up to 7% relative to using the data, suggesting that new diffuse models are required for high latitudes. Copyright © 2013 John Wiley & Sons, Ltd.