Atmospheric radiative transfer simulation for atmospheric correction of remote sensing data

IntroductionThe radiance leaving the earth-atmosphere sys-tem which can be sensed by a satellite borne ra-diometer is the sum of radiation emission fromtheearth surface and each atmospheric level that aretransmittedtothe top of the atmosphere.The radia-tion emissionfromthe earthsurface andthe radianceof each atmospheric level can be separated fromtheradiance at the top the atmospheric level a satellitemeasured.Thus,the earth surface parameters willbe retrieved from the surface radiance after a…     

热红外波段大气透过率和程辐射的估算方法

文中对M ONTRAN模型内嵌6种大气模式的主要特性差异进行分析,并以中纬度夏季大气模式为例,分析了主要参数(如水汽、臭氧以及气温等)对估算热红外波段大气透过率和程辐射的影响。论文最后对利用探空数据构造完整大气模式进行了研究。     

PMODTRAN: a parallel implementation based on MODTRAN for massive remote sensing data processing

MODerate resolution atmospheric TRANsmission (MODTRAN) is a commercial remote sensing (RS) software package that has been widely used to simulate radiative transfer of electromagnetic radiation through the Earth's atmosphere and the radiation observed by a remote sensor. However, when very large RS datasets must be processed in simulation applications at a global scale, it is extremely time-consuming to operate MODTRAN on a modern workstation. Under this circumstance, the use of parallel cluster computing to speed up the process becomes vital to this time-consuming task. This paper presents PMODTRAN, an implementation of a parallel task-scheduling algorithm based on MODTRAN. PMODTRAN was able to reduce the processing time of the test cases used here from over 4.4 months on a workstation to less than a week on a local computer cluster. In addition, PMODTRAN can distribute tasks with different levels of granularity and has some extra features, such as dynamic load balancing and parameter checking.     

CBERS-02卫星数据大气校正的快速算法

研究中巴资源卫星CBERS-02卫星数据大气校正的快速算法。首先假设地表为朗伯体，利用MODTRAN4．0软件模拟大气状况，讨论了不同地表反射率对大气校正参数的影响；然后计算出大气校正参数，生成查找表，根据CBERS卫星图像的不同情况确定不同的大气校正参数，从而对整幅图像进行大气校正。最后，利用核驱动模型对地表进行BRDF校正。     

Atmospheric radiative transfer simulation for atmospheric correction of remote sensing data

The radiance leaving the earth-atmosphere system which can be sensed by a satellite borne radiometer is the sum of radiation emission from the earth surface and each atmospheric level that are transmitted to the top of the atmosphere. The radiation emission from the earth surface and the radiance of each atmospheric level can be separated from the radiance at the top the atmospheric level measured by a satellite borne radiometer. However, it is very difficult to measure the atmospheric radiance, especially the synchronous measurement with the satellite. Thus some atmospheric radiative transfer models have been developed to provide many options for modeling atmospheric radiation transport, such as LOWTRAN, MODTRAN, 6S, FASCODE, LBLRTM, SHARC, and SAMM. Meanwhile, these models can support the detailed detector system design, the optimization and evaluation of satellite mission parameters, and the data processing procedures. As an example, the newly atmospheric radiative transfer models, MODTRAN will be compared with other models after the atmospheric radiative transfer is described. And the atmospheric radiative transfer simulation procedures and their applications to atmospheric transmittance, retrieval of atmospheric elements, and surface parameters, will also be presented.     

基于MODTRAN模式与卫星资料的晴空净太阳辐射模拟

探讨了中分辨率大气辐射传输模式MODTRAN4.0与卫星资料同化在模拟净太阳辐射中的应用,并利用CERES卫星资料作为MODTRAN模式输入参数,对2005年北京上甸子进行了晴空下的地表净太阳辐射模拟与比较。结果表明:利用MODTRAN4.0模式和CERES卫星资料可以较为精确地模拟晴空天气下的净太阳辐射,平均绝对误差为25.74 W/m2,平均相对误差为4.98%。此外,对净太阳辐射的影响因子的研究表明:太阳天顶角、反照率、水汽含量、大气光学厚度与臭氧浓度等因子与净太阳辐射均呈负相关关系,且太阳天顶角与反照率影响较大,其余因子影响较小。     

地物反射光谱对MODIS近红外波段水汽反演影响的模拟分析

在近红外辐射传输方程的基础上,利用近红外波段水汽的不同吸收属性,在MODTRAN的模拟下,深入分析了基于MODIS近红外数据的可降水汽反演算法,并着重讨论了地物反射光谱非线性在可降水汽反演中的影响。研究结果显示,当波段间反射率之比不等于1时,MODIS近红外波段反演水汽将存在较大偏差。同时,在地物光谱库基础上,计算了不同地物反射率比值,其分布表明,大部分地物波段反射率比值不等于1。研究表明,应用现有MODIS近红外波段水汽反演算法,如果不考虑地表反射率光谱变化的影响,由地表反射光谱造成的误差最大约为反射率比值与1偏差的15倍,同时,这一误差还与大气波段透过率之比有关。     

TOMRADE和MODTRAN 3.7模式研究紫外后向散射探测臭氧总量问题的比较

本文利用MODTRAN 3.7和TOMRADE模式分别计算了308.0 nm、312.5 nm、317.5 nm、322.3 nm、331.2 nm、360.0 nm六个紫外波段的后向散射强度并进行了比较,且利用两个模式计算得到的插值表,对EPTOMS实测资料分别进行反演,得到结论如下：1）两模式算得的后向散射强度随着太阳天顶角、卫星天顶角、地表反照率的变化特性基本一致,均能较好的反映紫外后向散射的辐射特性;2）总体而言,两模式计算的后向散射强度值相对偏差在－6％～18％之间;3）分别把MODTRAN 3.7和TOMRADE模式计算的插值表用于2003年7月30日中纬度地区EPTOMS实测资料的反演,得到的臭氧总量相对偏差在－3％～5％之间.本文对紫外波段大气辐射传输模式的研究和紫外后向散射探测臭氧总量的反演误差研究有着重要意义.     

高分四号静止卫星辐射性能模拟与信噪比分析——以香港近海岸水体为例

随着高分四号(GF-4号)地球同步卫星的发射与初步应用,其兼顾高空间与高时间分辨率的优势在同类型卫星中独具特色,中国对地静止卫星影像的研究也越来越受到重视。为了对GF-4号卫星在轨探测能力进行评估,掌握日内可用影像数据时段以合理安排成像时间提高卫星使用效率与延长寿命,有必要对以暗像元为代表的典型地物(如水体)进行辐射能模拟与信噪比研究。基于MODTRAN辐射传输模型,将香港沿岸水体作为暗目标,对GF-4号静止卫星多光谱遥感全色谱段以及蓝、绿、红、近红外4个多光谱谱段进行标准大气条件下入瞳处辐亮度的模拟,并利用在轨影像进行验证。在此基础上去除大气背景辐射干扰计算有效信噪比,并分别选取一年中春分、夏至、秋分、冬至,4个典型日的模拟数据进行质量分析,探讨一天连续观测中卫星能够获取高质量水体影像的有效时段,尤其是对晨昏时段临界微弱信号的敏感性进行分析。结果表明,夏至、冬至日内表观辐亮度峰值依次为59.26 W/(m~2·sr·μm)、56.20 W/(m~2·sr·μm),均出现在蓝光谱段;夏至、冬至最高地表有效辐亮度分别为17.52 W/(m~2·sr·μm)、12.13 W/(m~2·sr·μm),出现在蓝光谱段,但差距有所缩小。这是由于入瞳处辐射主要受到大气背景辐射的影响,以夏至正午为例,各谱段受背景辐射影响程度达到49.7%—75.5%。为规避背景辐射噪声,提出适用于陆表观测的有效辐射百分比的概念,推导出传统信噪比、有效信噪比以及有效辐射百分比之间的转换关系式,揭示了背景辐射对成像信噪比干扰的定量形式,提出有效信噪比计算方法,并以此为依据,以香港海岸带水体为目标,建立了相应有效信噪比对应时刻表。经计算香港海岸带水体一年中卫星全天有效信噪比均低于50 dB,夏至、冬至最高地表有效信噪比分别为41.0 dB、38.2 dB,其中蓝光谱段模拟效果最差,近红外、全色谱段结果较好。为保障影像质量,以香港海岸带水体有效信噪比35 dB为阈值确定影像获取时段,分别为夏至日北京时间7:49—17:01,冬至日北京时间9:28—15:07。     

Relative Radiometric Normalisation - performance testing of selected techniques and impact analysis on vegetation and water bodies

In this paper, six image-based Relative Radiometric Normalization (RRN) techniques were applied to normalize the bi-temporal Landsat 5 TM data-set. RRN techniques do not require any atmospheric and ground information at the time of image acquisition. The target image for the year 2009 was normalized in such a way that it resembled the atmospheric and sensor conditions similar to those under which the reference image of the same season for the year 1990 was acquired. Among the selected methods applied, it was found that the Iteratively Reweighted Multivariate Alteration Detection (IR-MAD) method performed better, based on the error statistic. The IR-MAD technique was found to be advantageous as it identified a large set of true time-invariant pixels automatically from the change background using iterative canonical component analysis. The technique also stretches the values of Normalized Difference Vegetation Index and Normalized Difference Water Index and may help to distinguish different vegetation and water bodies better.