短波红外CO2反演过程约束研究及初步反演结果

短波红外通道卫星CO2遥感是近年国际研究热点。首先,开展了卫星观测对气溶胶及大气温度的敏感性研究;其次,针对基于最优化理论的非线性迭代反演方法反演过程中的不收敛问题,提出了修正的阻尼牛顿方法(MDNM),并利用模拟数据评估了MDNM方法的有效性;最后,利用GOSAT卫星数据反演CO2的垂直混合比浓度,并与地基TCCON站点数进行比对。研究结果表明:短波近红外CO2卫星遥感受气溶胶散射及温度影响明显;通过地基比对初步验证了MDNM具有良好的精度,两者的相关性R2达到了0.729。     

大气CO2浓度卫星遥感进展

大气CO2是重要的温室气体,CO2浓度及其空间分布是全球气候变化评估中的主要不确定性因素之一。从1998年以来,卫星遥感大气CO2成为获取全球CO2的重要手段。本文阐述了现阶段大气CO2浓度卫星遥感反演进展情况,包括CO2探测载荷、反演算法和算法验证等。同时,论文详细介绍了近红外波段和热红外波段的反演算法特点和不确定因素,并针对CO2反演应用需求提出了展望。     

Remote Sensing for Martian Studies: Inferences from Syrtis Major

Remote sensing techniques have proved to be highly efficient in the exploration of Mars. Availability of several sensors operating across the electromagnetic spectrum on-board orbiters, landers and rovers has helped better understand the surface and atmospheric conditions on the Red planet. This article summarises the application potential of the sensors operating in different wavelength regions for Martian surface studies. Mars unlike Earth allows for utilizing remote sensing techniques in the complete thermal infrared region, owing to narrow absorption regions from a singularly dominant CO₂ atmosphere which facilitate detailed lithological mapping. This work also reviews various methodologies adopted till date to study the lithology, mineralogy and fluvial geomorphology including inferences from Syrtis Major volcanic construct. It is evident from the studies, Syrtis Major has well developed fluvial channels mostly attributed to lava flows. However, spectroscopic studies reveal the presence of hydroxylated and hydrated minerals which indicate that lava might not be the sole factor resulting in channel generation in the construct. Future space missions with high resolution payloads targeting this volcanic construct are indispensable to study these channels in detail.     

Application of hyperspectral remote sensing reflectance data to photochemical rate calculations in the Duplin River,a tidal river on the coast of Georgia,USA

Estuaries are photochemically dynamic environments with high carbon loads and relatively small areas. The small area poses problems for large-scale satellite-based remote sensing calculations, where the resolution is too coarse to distinguish land from water. Airborne remote sensing instruments have the potential to reveal the dynamics of these areas with fine-scale resolution. In June 2006, hyperspectral remote sensing imagery, using an AISA Eagle instrument, was collected over the tidal Duplin River, Georgia, USA. A dark-water updated version of the SeaUV algorithm was applied to the AISA remote sensing image to determine diffuse attenuation constants in the ultraviolet and calculate surface photochemical production rates of two inorganic products – carbon monoxide (CO) and carbon dioxide (CO₂). For an average day in June at the study site, the modeled photoproduction rates for CO₂ and CO averaged ~7 × 10^?1 nmol C/day/cm³ and ~3.5 × 10^?2 nmol C/day/cm³, respectively.     

O2-O2云反演算法及其在TROPOMI上的应用

利用遥感技术对大气环境污染进行监测时，云是影响痕量气体反演精度的重要因素，因此在痕量气体反演中需要对云的影响进行校正，通常使用的云参数主要是有效云量和云压。本文基于O₂-O₂ 477 nm吸收波段构建了O₂-O₂云反演算法：首先，根据有效云量和云高与连续反射率和O₂-O₂斜柱浓度之间的对应关系，结合假定的云模型利用VLIDORT辐射传输模型建立关于有效云量和云压的查找表；然后，通过差分吸收光谱技术拟合卫星载荷观测的大气层顶辐射，获得O₂-O₂斜柱浓度并计算连续反射率；最后，结合辅助数据，根据查找表进行插值反演获得有效云量和云压。通过将算法应用到OMI观测数据，将反演结果与OMCLDO2产品进行对比验证，有效云量和云压空间分布一致，相关系数R均超过0.97；并还将该算法应用于下一代大气成分监测仪器TROPOMI，与FRESCO+产品对比，有效云量和云压空间分布基本一致，当地表类型为海洋时，有效云量相关系数R大于0.97，云压相关系数R大于0.94，云压反演结果存在一定的区别；通过将O₂-O₂云反演算法和FRESCO+云压反演结果与CALIOP Cloud Layer产品进行对比，结果表明，在低云情况下，O₂-O₂云反演算法线性回归方程斜率为0.782，截距为198.0 hPa，相关系数R为0.850，算法表现优于FRESCO+。而在高云情况下，FRESCO+反演结果更接近CALIOP云压结果。在OMI和TROPOMI上的应用表明O₂-O₂云反演算法在大气云反演中具有较高的准确性和可行性，可以为大气痕量气体反演的校正提供云参数，并为中国同类型卫星载荷的云反演算法提供算法参考。     

星载大气探测激光雷达发展与展望

从最早的星载激光雷达空间技术实验LITE出发,回顾了已成功发射的多颗星载激光雷达发展历程。详细阐述了LITE、CALIPSO等星载激光雷达在大气遥感领域,特别是气候环境变化和数值预报模式研究上所取得的成就。主要从全球气溶胶垂直结构及其辐射强迫、全球云垂直结构和特征、气溶胶-云-降水相互作用和气溶胶数据在雾-霾和沙尘天气预报中的应用等4个方面进行展开说明,并且深入分析了未来星载激光雷达在大气风场和大气成分探测方面所面临的需求和挑战。在大气风场探测需求方面,结合星载激光雷达探测优势从提高热带地区的天气预报准确率、提高非地转条件下中小尺度短时临近预报水平和填补卫星高/低空急流监测技术空白等3个方面进行详细论述。在大气成分探测需求方面,与传统被动探测仪器相比较,突出激光雷达在信噪比、CO2垂直结构和夜间探测上的明显优势。最后,指出全球风场和大气成分探测将成为未来星载激光雷达的重要发展方向。     

湖泊碳循环研究中遥感技术的机遇与挑战

湖泊碳循环是全球碳循环过程中的重要环节,随着全球碳循环研究的不断深入,湖泊碳循环对全球碳循环的影响,以及其对全球气候变化的调节作用越来越受到关注.然而,由于湖泊分布的破碎性(大于0.002 km2的湖泊约有1.17×108个,并零星地分布在全球)和多样性(流域生态多样性,湖泊类型多样性,分布的气候带多样性等),使得全面...     

Estimates of CO2 from fires in the United States: implications for carbon management

Background  

Fires emit significant amounts of CO₂ to the atmosphere. These emissions, however, are highly variable in both space and time. Additionally, CO₂ emissions estimates from fires are very uncertain. The combination of high spatial and temporal variability and substantial uncertainty associated with fire CO₂ emissions can be problematic to efforts to develop remote sensing, monitoring, and inverse modeling techniques to quantify carbon fluxes at the continental scale. Policy and carbon management decisions based on atmospheric sampling/modeling techniques must account for the impact of fire CO₂ emissions; a task that may prove very difficult for the foreseeable future. This paper addresses the variability of CO₂ emissions from fires across the US, how these emissions compare to anthropogenic emissions of CO₂ and Net Primary Productivity, and the potential implications for monitoring programs and policy development.     

北京城市下垫面大气CO2反演算法

大气温室气体监测仪GMI（Greenhouse gases Monitor Instrument）是高分五号（GF-5）卫星载荷之一，主要用于全球温室气体含量监测和碳循环研究。高精度反演是卫星大气CO₂遥感的基本需求。地表反射率影响卫星遥感辐射量及辐射传输过程中的地气耦合过程，严重制约着CO₂的反演精度，针对GMI开发高精度的大气CO₂反演算法，地表反射是一个需要重点考虑的因素。城市是CO₂重要的发射源，且城市下垫面存在明显的二向反射特性，加上城市大气条件不良，复杂的地气耦合效应存在这都考验反演算法的准确性和鲁棒性。本文针对北京城市地区，利用2011年—2016年共5年的MODIS（MODerate-resolution Imaging Spectroradiometer）地表二向反射分布函数BRDF（Bidirectional Reflectance Distribution Function）数据，构建了适合利用单次观测数据反演的BRDF模型，并提出一种同时反演地表BRDF参数和大气CO₂含量的算法。结果表明在550 nm波长处气溶胶光学厚度AOD（Aerosol Optical Depth）小于0.4时，大部分GMI模拟数据的反演误差控制在0.5%（~2 ppm）内。利用GOSAT （Greenhouse gases Observing SATellite）实测数据的反演结果与修正后的日本国立环境研究所NIES（National Institute for Environmental Studies）反演结果进行对比，其平均误差为1.25 ppm，相关性达到0.85。本算法满足GMI数据在北京城市区域高精度CO₂反演的需求，并使得反演高值气溶胶区域数据成为可能，增加了GMI观测数据的利用率。     

CO2 concentration and its spatiotemporal variation in the troposphere using multi-sensor satellite data,carbon tracker,and aircraft observations

Satellite-based atmospheric CO₂ observations have provided a great opportunity to improve our understanding of the global carbon cycle. However, thermal infrared (TIR)-based satellite observations, which are useful for the investigation of vertical distribution and the transport of CO₂, have not yet been studied as much as the column amount products derived from shortwave infrared data. In this study, TIR-based satellite CO₂ products – from Atmospheric Infrared Sounder, Tropospheric Emission Spectrometer (TES), and Thermal And Near infrared Sensor for carbon Observation – and carbon tracker mole fraction data were compared with in situ Comprehensive Observation Network for Trace gases by AIrLiner (CONTRAIL) data for different locations. The TES CO₂ product showed the best agreement with CONTRAIL CO₂ data resulting in R² ~ 0.87 and root-mean-square error ~0.9. The vertical distribution of CO₂ derived by TES strongly depends on the geophysical characteristics of an area. Two different climate regions (i.e., southeastern Japan and southeastern Australia) were examined in terms of the vertical distribution and transport of CO₂. Results show that while vertical distribution of CO₂ around southeastern Japan was mainly controlled by horizontal and vertical winds, horizontal wind might be a major factor to control the CO₂ transport around southeastern Australia. In addition, the vertical transport of CO₂ also varies by region, which is mainly controlled by anthropogenic CO₂, and horizontal and omega winds. This study improves our understanding of vertical distribution and the transport of CO₂, both of which vary by region, using TIR-based satellite CO₂ observations and meteorological variables.     

大气PM2.5遥感制图研究进展

遥感技术具有时空大范围、低成本的独特优势,已经成为定量监测大气PM_(2.5)污染时空分布的重要手段。本文综述了大气PM_(2.5)遥感制图的进展:首先,对大气PM_(2.5)遥感反演方法进行了归纳,以及总结了现有大气PM_(2.5)遥感反演验证方法的适用条件与局限性;其次,对卫星反演大气PM_(2.5)合成产品偏差校正和大气PM_(2.5)无缝制图进行了梳理;最后总结了大气PM_(2.5)遥感制图的前沿研究方向。     

长春净月潭遥感试验场大气光学特性研究

中国科学院长春净月潭遥感试验场是对国内外开放的进行遥感实验研究的场地。为了高质量地进行对地定量遥感，必须了解该场上空大气气溶胶的光学特性，以便进行有效的大气订正。另一方面大气气溶胶本身也是遥感的对象。为提供这一背景性信息，本工作利用试验场所装备的太阳直接辐照光谱仪在１９９０年（无火山活动期）与１９９１年（强火山爆发期）两年进行的观测，经分析整理和反演推导，获得该站上空气溶胶引起的光学厚度（消光）谱和由此反演得到的气溶胶粒子谱分布。由于两年分别代表火山平静和活动期的情况，所得结果将为该地区遥感大气订正提供依据，同时可供其它北半球中纬地区参考。     

Carbon fluxes in ecosystems of Yellowstone National Park predicted from remote sensing data and simulation modeling

Background

A simulation model based on remote sensing data for spatial vegetation properties has been used to estimate ecosystem carbon fluxes across Yellowstone National Park (YNP). The CASA (Carnegie Ames Stanford Approach) model was applied at a regional scale to estimate seasonal and annual carbon fluxes as net primary production (NPP) and soil respiration components. Predicted net ecosystem production (NEP) flux of CO₂ is estimated from the model for carbon sinks and sources over multi-year periods that varied in climate and (wildfire) disturbance histories. Monthly Enhanced Vegetation Index (EVI) image coverages from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) instrument (from 2000 to 2006) were direct inputs to the model. New map products have been added to CASA from airborne remote sensing of coarse woody debris (CWD) in areas burned by wildfires over the past two decades.

Results

Model results indicated that relatively cooler and wetter summer growing seasons were the most favorable for annual plant production and net ecosystem carbon gains in representative landscapes of YNP. When summed across vegetation class areas, the predominance of evergreen forest and shrubland (sagebrush) cover was evident, with these two classes together accounting for 88% of the total annual NPP flux of 2.5 Tg C yr^-1 (1 Tg = 10¹² g) for the entire Yellowstone study area from 2000-2006. Most vegetation classes were estimated as net ecosystem sinks of atmospheric CO₂ on annual basis, making the entire study area a moderate net sink of about +0.13 Tg C yr^-1. This average sink value for forested lands nonetheless masks the contribution of areas burned during the 1988 wildfires, which were estimated as net sources of CO₂ to the atmosphere, totaling to a NEP flux of -0.04 Tg C yr^-1 for the entire burned area. Several areas burned in the 1988 wildfires were estimated to be among the lowest in overall yearly NPP, namely the Hellroaring Fire, Mink Fire, and Falls Fire areas.

Conclusions

Rates of recovery for burned forest areas to pre-1988 biomass levels were estimated from a unique combination of remote sensing and CASA model predictions. Ecosystem production and carbon fluxes in the Greater Yellowstone Ecosystem (GYE) result from complex interactions between climate, forest age structure, and disturbance-recovery patterns of the landscape.     

MODIS和OMI数据评估阅兵期间北京市大气减排成效

卫星观测不仅能反映区域宏观大气污染状况,也能从城市尺度上监测大气污染物的变化。基于以上优势,本文利用MODIS气溶胶光学厚度(AOD)和OMI对流层NO_2垂直柱浓度数据,比较2015年与2012年—2014年以及2015年3个时期(减排前、减排中、减排后)AOD和NO_2柱浓度的变化,定性分析了阅兵期间华北平原地区污染物减排效果,重点定量评估北京市联控减排措施的效果。研究发现2015年减排中华北平原重污染地区AOD和NO_2柱浓度相比于前3年同期有明显降低。定量分析北京市的减排效果得到:2015年减排中较前3年同期而言,AOD降低59%,NO_2柱浓度降低41%;较2015年减排前而言,AOD降低73%,NO_2柱浓度降低30%,去除气象条件影响后,AOD下降43%,NO_2柱浓度下降21%,说明严格的联控减排措施有效地改善了空气质量,气象条件也起到积极的作用。减排措施结束后,AOD和NO_2柱浓度比减排中分别增加159%和71%。研究结果表明,卫星遥感与地基监测评估效果相当,能反映北京地面污染物排放能力;它既能观测区域尺度大气污染变化,又可评估城市尺度大气污染减排。随着卫星技术水平的提高,期望未来卫星遥感可作为一种独立手段来定量评估区域及城市尺度空气质量减排措施的效果。     

基于大气温度和水汽含量改进HJ-1B地表温度反演

为了提高地面气象站稀少地区地表温度遥感反演的精度,本文基于多源遥感数据的优势,首先利用MODIS影像获取研究区像元尺度上平均大气水汽含量;然后利用同时相的HJ-1B影像估算区域地表比辐射率,再采用温度-植被指数法获取近地表大气温度;最后将以上3个参数输入单窗体算法,改进其地表温度反演的精度。研究结果表明,改进单窗体算法反演地表温度与地面实测温度的偏差小于1 K,为地面气象站点稀少的植被覆盖区域提供了一种可行的精确遥感反演地表温度方法。     

Methane emission modelling using MODIS thermal and optical data: A case study on Gujarat

Wetlands are one of the most important sources of atmospheric methane (CH₄) contributing about 22% to the global methane budget. But to improve estimates of CH₄ emission at regional and global scales there is a need to observe the sources such as wetlands frequently and develop process-based models. In this regard, wetland inventory using satellite remote sensing data has conventionally been carried out by analysis of optical data. Due to thermal inertia differences emittive thermal channels data has shown promise to provide highly critical information about wetlands such as water spread, aquatic vegetation and mud flats etc. Thermal channels data of MODIS (Moderate Resolution Imaging Spectroradiometer) sensor with a spatial resolution of 1km and swath of 2330 km is emerging as the key source of remote sensing data for global/ regional wetland estimation and assessment of green house gas emission. In the present study MODIS thermal channels (31 and 32) and optical channels (1,2, and 3) data have been used for evaluating methane emission from wetlands in Gujarat. An empirical model based on temperature and productivity has been used to investigate the response of methane emission from different sources. Model has the potential to estimate country level methane emission based on satellite remote sensing in conjunction with collateral data/information. In this study. MODIS data of two dates pertaining to Gujarat have been analyzed and results compared with respect to methane emission.     

杭州湾HJ CCD影像悬浮泥沙遥感定量反演

利用环境小卫星CCD(HJ CCD)影像对杭州湾悬浮泥沙浓度(SSC)进行了反演研究。通过对杭州湾水体遥感反射率(Rrs)与SSC进行相关性分析发现,在690nm和830nm左右出现显著的反射峰,分别位于HJ CCD影像的第3和第4波段范围内;大于700nm波长处的Rrs与SSC相关性较好。基于实测Rrs和SSC之间的相关关系,利用第4和第3波段比值作为遥感因子建立SSC反演模型,模型决定系数达到0.90。借鉴近红外-短波红外(NIR-SWIR)结合的大气校正方法反演出的准同步MODIS气溶胶数据,实现了HJ CCD影像的大气校正,第3、第4波段的大气校正结果相对误差分别为5.54%和6.97%。结果显示,HJ CCD影像反演的SSC相对误差为7.12%;杭州湾悬浮泥沙浓度要显著高于长江口,且内部差异明显。研究表明,通过适当的大气校正方法和反演算法,HJ CCD影像可用于杭州湾悬浮泥沙浓度的估计。     

遥感理论模式研究的几个问题

本文简要地评论近年来微波遥感理论模式研究的进展,主要包括遥感对象理论模拟的随机离散散射粒子介质,连续随机介质,和随机粗糙表面的电磁散射和热辐射的理论,定量的数值求解方法,以及它们在地表植被、土壤、冰雪、大气云雨、海冰、风驱海面等主动和被动遥感中的应用。随着今后遥感技术的发展,要更为精细地模拟自然界中遥感对象及其环境,给出定量的数学物理学方法,进行定量的数据分析和遥感参数反演,还有大量的工作有待于研究。本文讨论了当今遥感理论模式研究中还存在的问题,提出了今后要予以研究的若干个方向性工作。     

大气程辐射遥感图像与城市大气污染监测研究

作为对地探测的遥感技术所获取的遥感图像包含了地面和大气信息,并且主要是地面信息.利用地面反射率分布图像将遥感数字图像中弱的大气信息与强的地面目标信息分离,生成仅仅包含大气信息的大气程辐射遥感图像.利用多(高)光谱遥感数字图像中不同波段的大气程辐射遥感图像可以不受地面干扰地对城市大气污染的类型和程度(气溶胶粒径和含量)进行遥感监测.在大气污染地面观测数据(可吸入颗粒物PM10浓度)的支持下,利用MODIS多光谱遥感数字图像生成的对应多光谱大气程辐射遥感数字图像,以上海市为例进行了城市大气污染遥感监测的原理方法研究.     

Diffusion Source Detection of Volcanic Ash Cloud Using MODIS Satellite Data

The massive volcanic ash cloud not only causes obvious global climate and environmental changes, but also threatens aviation safety under the background of globalization. The diffusion source detection is a key factor in the volcanic ash cloud monitoring and the diffusion research. Taking the Eyjafjallajokull’s volcanic ash cloud on April 19, 2010 in Iceland as an example, based on the analysis of the absorption spectrum characteristics in the thermal infrared spectral range, in this paper, a new diffusion source detection algorithm of volcanic ash cloud combining split window algorithm with SO₂ concentration distribution is proposed from the moderate resolution imaging spectroradiometer (MODIS) satellite remote sensing images; subsequently the ash radiance index (ARI) and absorbing aerosol index (AAI) are applied as contrast to the detection results. The results show that the proposed algorithm can effectively detect the diffusion source of volcanic ash cloud, and has high consistency with the ARI and AAI distributions, and has certain potential applications in improving the detection effect of volcanic ash cloud and prediction accuracy of diffusion model.