Time–space continuity of daily maps of fractional snow cover and albedo from MODIS     

Jeff Dozier  Thomas H. Painter  Karl Rittger  James E. Frew 《Advances in water resources》2008

Using reflectance values from the seven MODIS “land” bands with 250 or 500 m resolution, along with a corresponding cloud product, we estimate the fraction of each 500 m pixel that snow covers, along with the albedo of that snow. The daily products have data gaps and errors because of cloud cover and sensor viewing geometry. Rather than make users interpolate and filter these patchy daily maps without completely understanding the retrieval algorithm and instrument properties, we use the daily time series to improve the estimate of the measured snow properties for a particular day. We use a combination of noise filtering, snow/cloud discrimination, and interpolation and smoothing to produce our best estimate of the daily snow cover and albedo. We consider two modes: one is the “predictive” mode, whereby we estimate the snow-covered area and albedo on that day using only the data up to that day; the other is the “retrospective” mode, whereby we reconstruct the history of the snow properties for a previous period.  相似文献   

玉米冠层反射率及净辐射的估算   总被引：1，自引：0，他引：1  

吕厚荃  于贵瑞 《应用气象学报》1999,10(4):421-427

在1994~1996年3年田间试验的基础上,根据玉米生长状况及其冠层特征,选取包括植株高度、平均叶面积密度、农田覆被率等植物特征量组成的植物参数——综合植被系数来描述玉米冠层状况,并以此为因子来估算玉米冠层的反射率和净辐射,取得了良好的结果。  相似文献   

Modeling of the radial and transverse components of the albedo function     

Afaf M. Abd El-Hameed  K. I. Khalil  Y. E. Helali 《Astrophysics and Space Science》2009,320(4):315-320

In this work, we shall confine ourselves to solve analytically the integrals called , for the two components of albedo radiation pressure on an Earth’s satellite. When the Earth’s albedo is variable, as far as we know, this case has not been dealt with analytically. We shall solve these two integrals when the satellite’ horizon is illuminated and when the sun lies on the equator. This approach will facilitate the evaluation of the mentioned two equations. We will also compare our results with previous works obtained numerically.  相似文献   

基于DEM的ETM⁺图像辐射校正及汉江流域反照率的计算   总被引：3，自引：0，他引：3  

朱叶飞  张万昌  蒋建军 《国土资源遥感》2004,15(3):8-13

对Gilabert[1]大气校正方法进行改进,提出了一种简单易行的辐射校正方法。该方法只需从ETM⁺图像上获取两个不同海拔高程的暗像元,再依据DEM进行大气校正,反演出各个高程上的大气及辐射参数,并在此基础上进行地形校正,进而获取LandsatETM⁺1～5和7波段的地表反射率,通过对各窄波段地表反射率的线性组合获取反照率。结果表明,该方法可行,精度较高。  相似文献   

降水条件下的典型干旱区陆面特征模拟验证   总被引：6，自引：0，他引：6       下载免费PDF全文

王胜  张强  卫国安 《地球物理学报》2006,49(2):383-390

利用“我国西北干旱区陆－气相互作用观测试验"在敦煌双墩子戈壁站取得的观测资料及最近的一些研究成果对陆面模式中反照率、相似性函数及地表粗糙度(动量粗糙度，标量粗糙度)3个方面的参数化方案进行了改进，然后对一次典型降水过程的陆面特征及近地层的风、温、湿进行了模拟.结果表明：改进的模式能对降水条件下的干旱区陆面特征进行较好的模拟，其中对辐射、地表温度的模拟相当好，而对能量的模拟虽然还有要改进的地方，但总体结果令人满意；另外改进后的模式对近地层的温度和湿度的模拟也有明显的改善.  相似文献   

绿洲边缘内外近地面辐射收支分析   总被引：7，自引：6，他引：7  

文军  王介民 《高原气象》1997,16(4):359-366

  相似文献   

Long-term comparisons of net radiation calculation schemes   总被引：1，自引：0，他引：1  

J. H. Kjaersgaard  R. H. Cuenca  F. L. Plauborg  S. Hansen 《Boundary-Layer Meteorology》2007,123(3):417-431

Six commonly used models for calculating daily net radiation were tested against measured net radiation. Meteorological data from 32 and 7 consecutive years obtained at two temperate sites were used. The extensive duration of the datasets ensured that all weather conditions and extreme events were captured. A set of statistical procedures was used to evaluate the performance of the models. The mean bias errors ranged from 0.0 W m⁻² to 24.8 W m⁻² and 0.1–24.7 W m⁻² and root mean square error from 11.0 W m⁻² to 28.1 W m⁻² and 10.0–27.9 W m⁻² at the two sites respectively, for days without snow cover on the ground. The best agreement was found when locally calibrated model coefficients were used. Only negligible differences in model performances were found between the two sites and the differences were lower than the inaccuracies of the net radiation instruments used. Including days with snow cover in the analysis lead to a slight increase in the bias and scatter of the predictions. Model performances were in general better during summertime than wintertime. Altered albedo values during winter caused by generally low sun angles were likely the cause of this. Analysis showed that at least 5 years of data were needed to obtain stable calibration coefficients for local calibration of the models. Based on the results from this study, and due to their physical background, two physical based models were recommended for calculating daily values of net radiation under temperate climate regimes. A simple adjustment of the calibration coefficients based on climate regime was suggested for these models.  相似文献   

Calculation of solar albedo and radiation equilibrium over the Qinghai-Xizang Plateau and analysis of their climatic features   总被引：1，自引：0，他引：1  

Zhao Ping  Chen Longxun 《大气科学进展》2000,17(1):140-156

1.IntroductionTopreciselyestimatethevaluesofalbedosatsurfaceandatmospherictop.surfacetotalradiationandearth--atmosphereoutgoinglongwaveradiationiscrucialtocalculatingradiationbalanceatsurfaceandatmospherictopandexploringoftheeffectoftheQXPatmosphericheatsourcesonatmosphericcirculations.Using1958--1960observationsofsurfacetotalradiation,albedoandsurfacemeteorologicalobservationsoverChina.ChenandGongetal.(1964.1965)investigated,throughanatmosphericradiationcalculationscheme.thedistributionchar…  相似文献   

沙尘源区LST/Albedo时序变化与TSP的对比分析——以2001年春季中国北方强沙尘过程为例     

韩秀珍  刘志丽  马建文  张小曳 《地理研究》2004,23(1):19-28

20 0 1年春季 ,中国北方多次受到沙尘天气的影响 ,给人们的生产、生活带来严重的威胁 ,引起了亚洲国家的广泛重视。利用卫星监测数据采集沙尘云图变化、运移路径、地表覆盖和沙尘过程中的地面反照率、温度、湿度、粗糙度等物理参数反演实验结果 ,可以弥补地面观测站点稀少、数据不连续的缺陷。本文以 2 0 0 1年 3月到 5月的几次沙尘天气为例 ,介绍基于地表覆盖的AVHRR的LST/Albedo反演结果与TSP (沙尘干量 )对比分析 ,发现它们具有较好的相关性。从而反映了沙尘暴发生前后地表能量的变化状况 ,能为预测预警沙尘天气的危害提供及时客观的空间信息。  相似文献   

黑河流域地表反照率估算及其时空特征分析     

Wu Shengbiao  Wen Jianguang  Liu Qiang  Dou Baocheng  You Dongqin 《地球科学进展》2015,30(6):680-690

基于不同空间尺度、长时间序列的地表反照率产品探究黑河流域2000—2012年的反照率时空变化特征。首先基于角度格网化(AB)算法对黑河流域30 m环境卫星一号HJ-1/CCD大气层顶方向反射率进行了地表反照率估算,作为高空间分辨率的地表反照率产品;选择同种算法计算的1 km空间分辨率的Global LAnd Surface Satellite(GLASS)反照率产品作为低空间分辨率反照率产品。结果表明:1利用AB算法反演的HJ卫星反照率具有较高精度,满足流域尺度反照率时空特征分析的精度要求;2黑河流域地表反照率空间分布差异显著,流域上游植被覆盖区域反照率较低,中下游荒漠地表反照率较高;3流域地表反照率的年内变化与季节性降雪和作物物候周期性变化一致。从季节变化角度,黑河流域反照率月平均值的年变化呈"U"字型,其中,冬季反照率最高,春季和秋季次之,夏季最低。从年际变化角度,黑河下游反照率呈上升趋势,上游和整个流域呈下降趋势。  相似文献