地表反射率是控制地表能量平衡的一个重要参数。城市建筑物的分布具有较大的不均一性,这不仅给地基观测城市地表反射率带来了很大困难,数值模拟城市地表反射率也是非常困难的。作者开发了一个三维城市地表反射率模式city_photo,该方法...地表反射率是控制地表能量平衡的一个重要参数。城市建筑物的分布具有较大的不均一性,这不仅给地基观测城市地表反射率带来了很大困难,数值模拟城市地表反射率也是非常困难的。作者开发了一个三维城市地表反射率模式city_photo,该方法结合了蒙特卡洛方法和几何光学方法的优点,具有较高的精度和较快的计算速度。通过引入城市地图的概念,该模式能够计算具有不同结构的城市的地表反射率。2002至2004年晴空MODIS（MODerate Resolution Imaging Spectroradiometer,中分辨率成像光谱辐射计）1-7通道可见光和近红外通道地表反射率资料被用来检验模式的有效性,位于北京朝阳区的中国科学院大气物理研究所的AERONET站点观测得到气溶胶光学特性和水汽资料,6S（Second Simulation of Satellite Signal in the Solar Spectrum）大气辐射传输模式被用来对其进行大气订正。模式计算的北京城市地表反射率个例与MODIS 7个通道地表反射率观测结果具有很高的相关性,相关系数在0.80-0.93之间,说明模式能够较好地模拟城市地表反射率随太阳和观测角度的变化情况。最后讨论了城市结构对城市地表反射率的影响。展开更多
Assessing large-scale patterns of gross primary production (GPP) in arid and semi-arid (ASA) areas is important for both scientific and practical purposes.Remote sensing-based models,which integrate satellite data wit...Assessing large-scale patterns of gross primary production (GPP) in arid and semi-arid (ASA) areas is important for both scientific and practical purposes.Remote sensing-based models,which integrate satellite data with input from ground-based meteorological measurements and vegetation characteristics,improve spatially extended estimates of vegetation productivity with high accuracy.In this study,the authors simulated GPP in ASA areas by integrating moderate resolution imaging spectral radiometer (MODIS) data with eddy covariance and meteorological measurements at the flux tower sites using the Vegetation Photosynthesis Model (VPM),which is a remote sensing-based model for analyzing the spatial pattern of GPP in different land cover types.The field data were collected by coordinating observations at nine stations in 2008.The results indicate that in the region during the growing season GPP was highest in cropland sites,second highest in woodland sites,and lowest in grassland sites.VPM captured the temporal and spatial characteristics of GPP for different land covers in ASA areas.Further,Enhanced Vegetation Index (EVI) had a strong liner relationship with GPP in densely vegetated areas,while the Normalized Difference Vegetation Index (NDVI) had a strong liner relationship with GPP over less dense vegetation.This study demonstrates the potential of satellite-driven models for scaling-up GPP,which is a key component for studying the carbon cycle at regional and global scales.展开更多
The Chinese Sun Hazemeter Network (CSHNET) provides the necessary ground-based observation to validate and assess the applicability of MODIS aerosol optical depth (AOD) products over different ecological and geographi...The Chinese Sun Hazemeter Network (CSHNET) provides the necessary ground-based observation to validate and assess the applicability of MODIS aerosol optical depth (AOD) products over different ecological and geographic regions in China for the first time. The validation results show that the comprehensive utilization ratio and applicability of MODIS products varied very much over different regions and seasons from August 2004 to July 2005. On the Tibetan Plateau, the comprehensive utili- zation ratio of MODIS data was low: MODIS products only accounted for 16% of the ground-based observation; on average, 31% to 45% of MODIS products fell within the retrieval errors issued by NASA. A similar result was found in northern desert areas with the ratio of MODIS to observation ranging from 15% to 55%, with 7% to 39% of MODIS products within errors. In the remote northeast corner of China, low ratios of MODIS to observation were also found ranging from 14% to 46%, with 49% to 69% of MODIS within errors. The forested sites exhibited moderate ratios of MODIS to observation ranging from 46% to 65%, with 30% to 59% of MODIS within errors. This was similar to numbers observed at sites along eastern seashore of China and inland urban sites with the ratio of MODIS to observation between 63% to 75%, with 25% to 67% of MODIS within errors for sites along eastern seashore of China and 43% to 78%, with 35% to 75% of MODIS within errors for inland urban sites. The ratio of MODIS to observation over agricultural areas ranged from 61% to 89%; 59%-88% of MODIS fell within the retrieval errors. At homogeneous and well vegetated areas, the comprehensive utilization ratio of MODIS products was over 80% and above 70% of MODIS products fell within the retrieval errors in growing season.展开更多
The ice shelves in the northern Antarctic Peninsula are highly sensitive to variations of temperature and have therefore served as indicators of global warming. In this study,we estimate the velocities of the ice shel...The ice shelves in the northern Antarctic Peninsula are highly sensitive to variations of temperature and have therefore served as indicators of global warming. In this study,we estimate the velocities of the ice shelves in the northern Antarctic Peninsula using co-registration of optically sensed images and correlation module(COSI-Corr) in the Environment for Visualizing Images(ENVI) based on Moderate Resolution Imaging Spectroradiometer(MODIS) images during 2000–2012,from which we conclude that the ice flow directions generally match the peninsulas pattern and the crevasse,ice flows mainly eastward into the Weddell Sea. The spatial pattern of velocity field exhibits an increasing trend from the western grounding line to the maximum at the middle part of the ice shelf front on Larsen C with a velocity of approximately 700 ma–1,and the velocity field shows relatively higher values in its southerly neighboring ice shelf(e.g. Smith Inlet). Additionally,ice flows are relatively quicker in the outer part of the ice shelf than in the inner parts. Temporal changes in surface velocities show a continuous increase from 2000 to 2012. It is worth noting that,the acceleration rate during 2000–2009 is relatively higher than that during 2009–2012,while the ice movement on the southern Larsen C and Smith Inlet shows a deceleration from 2009 to 2012.展开更多
Volcanic ash cloud has serious impacts on aviation.With volcanic ash dispersion,it also has a profound and long-term impact on climate and the environment.A new volcanic ash cloud detecting method (SWIR-TIR Volcanic A...Volcanic ash cloud has serious impacts on aviation.With volcanic ash dispersion,it also has a profound and long-term impact on climate and the environment.A new volcanic ash cloud detecting method (SWIR-TIR Volcanic Ash method,STVA) is presented that uses satellite images of Medium Resolution Spectral Imager (MERSI) and Visible and Infrared Radiometer (VIRR) on board the second generation Polar-Orbiting meteorological satellite of China (FY-3A).STVA is applied in detecting Iceland's Eyjafjallajokull volcano eruption.Compared with the traditional Split Window Temperature Difference method (SWTD),the results show that STVA is more sensitive to volcanic ash cloud than SWTD and can fairly extract volcanic ash information from the background of meteorological cloud and the ocean.Ash Radiance Index (ARI) and Absorbing Aerosol Index (AAI) derived from Metop-A satellite images are used to validate the performance of STVA.It is shown that STVA provides similar results with ARI and AAI.FY-3A/MERSI,VIRR and Terra /MODIS data are used to test STVA and SWTD.It is demonstrated that STVA derived from FY-3A satellite data is more effective in complicated meteorological conditions.This study shows great potential of using China's own new generation satellite data in future global volcanic ash cloud monitoring operation.展开更多
文摘地表反射率是控制地表能量平衡的一个重要参数。城市建筑物的分布具有较大的不均一性,这不仅给地基观测城市地表反射率带来了很大困难,数值模拟城市地表反射率也是非常困难的。作者开发了一个三维城市地表反射率模式city_photo,该方法结合了蒙特卡洛方法和几何光学方法的优点,具有较高的精度和较快的计算速度。通过引入城市地图的概念,该模式能够计算具有不同结构的城市的地表反射率。2002至2004年晴空MODIS（MODerate Resolution Imaging Spectroradiometer,中分辨率成像光谱辐射计）1-7通道可见光和近红外通道地表反射率资料被用来检验模式的有效性,位于北京朝阳区的中国科学院大气物理研究所的AERONET站点观测得到气溶胶光学特性和水汽资料,6S（Second Simulation of Satellite Signal in the Solar Spectrum）大气辐射传输模式被用来对其进行大气订正。模式计算的北京城市地表反射率个例与MODIS 7个通道地表反射率观测结果具有很高的相关性,相关系数在0.80-0.93之间,说明模式能够较好地模拟城市地表反射率随太阳和观测角度的变化情况。最后讨论了城市结构对城市地表反射率的影响。
基金supported by the National Basic Research Program of China (Grant Nos. 2009CB723904 and 2006CB400500)
文摘Assessing large-scale patterns of gross primary production (GPP) in arid and semi-arid (ASA) areas is important for both scientific and practical purposes.Remote sensing-based models,which integrate satellite data with input from ground-based meteorological measurements and vegetation characteristics,improve spatially extended estimates of vegetation productivity with high accuracy.In this study,the authors simulated GPP in ASA areas by integrating moderate resolution imaging spectral radiometer (MODIS) data with eddy covariance and meteorological measurements at the flux tower sites using the Vegetation Photosynthesis Model (VPM),which is a remote sensing-based model for analyzing the spatial pattern of GPP in different land cover types.The field data were collected by coordinating observations at nine stations in 2008.The results indicate that in the region during the growing season GPP was highest in cropland sites,second highest in woodland sites,and lowest in grassland sites.VPM captured the temporal and spatial characteristics of GPP for different land covers in ASA areas.Further,Enhanced Vegetation Index (EVI) had a strong liner relationship with GPP in densely vegetated areas,while the Normalized Difference Vegetation Index (NDVI) had a strong liner relationship with GPP over less dense vegetation.This study demonstrates the potential of satellite-driven models for scaling-up GPP,which is a key component for studying the carbon cycle at regional and global scales.
基金Supported by the National Natural Science Foundation of China (Grants Nos. 40675073, 40525016 and 40520120071)the National Basic Research Program (973) of China (Grant No. 2007CB407303)
文摘The Chinese Sun Hazemeter Network (CSHNET) provides the necessary ground-based observation to validate and assess the applicability of MODIS aerosol optical depth (AOD) products over different ecological and geographic regions in China for the first time. The validation results show that the comprehensive utilization ratio and applicability of MODIS products varied very much over different regions and seasons from August 2004 to July 2005. On the Tibetan Plateau, the comprehensive utili- zation ratio of MODIS data was low: MODIS products only accounted for 16% of the ground-based observation; on average, 31% to 45% of MODIS products fell within the retrieval errors issued by NASA. A similar result was found in northern desert areas with the ratio of MODIS to observation ranging from 15% to 55%, with 7% to 39% of MODIS products within errors. In the remote northeast corner of China, low ratios of MODIS to observation were also found ranging from 14% to 46%, with 49% to 69% of MODIS within errors. The forested sites exhibited moderate ratios of MODIS to observation ranging from 46% to 65%, with 30% to 59% of MODIS within errors. This was similar to numbers observed at sites along eastern seashore of China and inland urban sites with the ratio of MODIS to observation between 63% to 75%, with 25% to 67% of MODIS within errors for sites along eastern seashore of China and 43% to 78%, with 35% to 75% of MODIS within errors for inland urban sites. The ratio of MODIS to observation over agricultural areas ranged from 61% to 89%; 59%-88% of MODIS fell within the retrieval errors. At homogeneous and well vegetated areas, the comprehensive utilization ratio of MODIS products was over 80% and above 70% of MODIS products fell within the retrieval errors in growing season.
基金National Nature Science Foundation of China,No.41371391Chinese National Antarctic and Arctic Research Expedition,No.CHINARE2015-02-02+2 种基金Specialized Research Fund for the Doctoral Program of Higher Education of China,No.20120091110017A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)partially supported by Collaborative Innovation Center of Novel Software Technology and Industrialization
文摘The ice shelves in the northern Antarctic Peninsula are highly sensitive to variations of temperature and have therefore served as indicators of global warming. In this study,we estimate the velocities of the ice shelves in the northern Antarctic Peninsula using co-registration of optically sensed images and correlation module(COSI-Corr) in the Environment for Visualizing Images(ENVI) based on Moderate Resolution Imaging Spectroradiometer(MODIS) images during 2000–2012,from which we conclude that the ice flow directions generally match the peninsulas pattern and the crevasse,ice flows mainly eastward into the Weddell Sea. The spatial pattern of velocity field exhibits an increasing trend from the western grounding line to the maximum at the middle part of the ice shelf front on Larsen C with a velocity of approximately 700 ma–1,and the velocity field shows relatively higher values in its southerly neighboring ice shelf(e.g. Smith Inlet). Additionally,ice flows are relatively quicker in the outer part of the ice shelf than in the inner parts. Temporal changes in surface velocities show a continuous increase from 2000 to 2012. It is worth noting that,the acceleration rate during 2000–2009 is relatively higher than that during 2009–2012,while the ice movement on the southern Larsen C and Smith Inlet shows a deceleration from 2009 to 2012.
基金supported by National Basic Research Program of China (Grant No. 2010CB950700)
文摘Volcanic ash cloud has serious impacts on aviation.With volcanic ash dispersion,it also has a profound and long-term impact on climate and the environment.A new volcanic ash cloud detecting method (SWIR-TIR Volcanic Ash method,STVA) is presented that uses satellite images of Medium Resolution Spectral Imager (MERSI) and Visible and Infrared Radiometer (VIRR) on board the second generation Polar-Orbiting meteorological satellite of China (FY-3A).STVA is applied in detecting Iceland's Eyjafjallajokull volcano eruption.Compared with the traditional Split Window Temperature Difference method (SWTD),the results show that STVA is more sensitive to volcanic ash cloud than SWTD and can fairly extract volcanic ash information from the background of meteorological cloud and the ocean.Ash Radiance Index (ARI) and Absorbing Aerosol Index (AAI) derived from Metop-A satellite images are used to validate the performance of STVA.It is shown that STVA provides similar results with ARI and AAI.FY-3A/MERSI,VIRR and Terra /MODIS data are used to test STVA and SWTD.It is demonstrated that STVA derived from FY-3A satellite data is more effective in complicated meteorological conditions.This study shows great potential of using China's own new generation satellite data in future global volcanic ash cloud monitoring operation.
