Arctic nighttime land-surface temperatures derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the NASA Terra and Aqua satellites are investigated. We use the local equator crossing ti...Arctic nighttime land-surface temperatures derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the NASA Terra and Aqua satellites are investigated. We use the local equator crossing times of 22:30 and 01:30, respectively, in the analysis of changes, trends and variations on the Arctic region and within 120° sectors. We show increases in the number of days above 0°C and significant increase trends over their decadal periods of March 2000 through 2010 (MODIS Terra) and July 2002 through 2012 (MODIS Aqua). The MODIS Aqua nighttime Arctic land-surface temperature change, +0.2°C ± 0.2°C with P-value of 0.01 indicates a reduction relative to the MODIS Terra nighttime Arctic land-surface temperature change, +1.8°C ± 0.3°C with P-value of 0.01. This reduction is a decadal non-stationary component of the Arctic land-surface temperature changes. The reduction is greatest, -1.3°C ± 0.2°C with P-value of 0.01 in the Eastern Russia— Western North American sector of the Arctic during the July 2002 through 2012.展开更多
针对Aqua和Terra MODIS AOD数据利用线性回归算法拟合结果不够精确的问题,本文提出了二次多项式回归算法对其进行拟合,二次多项式是指这个多项式的项数超过1,且最高次方数为2。采用二次多项式回归和线性回归算法分别对2015年随机选择的...针对Aqua和Terra MODIS AOD数据利用线性回归算法拟合结果不够精确的问题,本文提出了二次多项式回归算法对其进行拟合,二次多项式是指这个多项式的项数超过1,且最高次方数为2。采用二次多项式回归和线性回归算法分别对2015年随机选择的一天和4—6月的AOD数据进行拟合,并将两种方法拟合的结果进行对比分析。研究结果显示,针对同一组Aqua和Terra MODIS AOD数据的拟合,二次多项式回归方法拟合得到的RMSE、MAE、R值比线性回归拟合方法得到的值精度都要高很多,说明二次多项式回归拟合方法在Aqua和Terra MODIS AOD数据的拟合方面优于线性回归方法的拟合,证明了二次多项式回归拟合方法适用于此方面的研究,而且能够提升Aqua和Terra MODIS AOD数据拟合结果的精度。展开更多
利用TERRA和AQUA共同反演气溶胶光学厚度和地表反射率特征,对其原理及方法进行了详细的讨论。通过Terra和Aqua两颗卫星对同一地点的不同角度的观测,结合多个光学通道的信息,反演了北京地区光学厚度及地表反射率信息。反演的气溶胶光学...利用TERRA和AQUA共同反演气溶胶光学厚度和地表反射率特征,对其原理及方法进行了详细的讨论。通过Terra和Aqua两颗卫星对同一地点的不同角度的观测,结合多个光学通道的信息,反演了北京地区光学厚度及地表反射率信息。反演的气溶胶光学厚度同地面观测的结果相比具有很好的一致性。同时,对地表反射率及气溶胶波长指数等也进行了讨论和对比,结果显示,对北京地区,MOD IS 1通道地表反射率和7通道地表反射率的比在0.66左右,3通道和7通道的比在0.28左右。相比于NASA暗背景全球反演算法中1、3通道和7通道的比为0.50和0.25的处理方法,反演得到的气溶胶光学厚度结果也较好。展开更多
The Moderate Resolution Imaging Spectroradiometer （MODIS） is one of the key instruments for NASA＇s Earth Observing System （EOS）, currently operating on both the Terra and Aqua satellites. The MODIS is a major adv...The Moderate Resolution Imaging Spectroradiometer （MODIS） is one of the key instruments for NASA＇s Earth Observing System （EOS）, currently operating on both the Terra and Aqua satellites. The MODIS is a major advance over the previous generation of sensors in terms of its spectral, spatial, and temporal resolutions. It has 36 spectral bands： 20 reflective solar bands （RSB） with center wavelengths from 0.41 to 2.1 μm and 16 thermal emissive bands （TEB） with center wavelengths from 3.7 to 14.4 μm, making observations at three spatial resolutions： 250 m （bands 1-2）, 500 m （bands 3-7）, and lkm （bands 8-36）. MODIS is a cross-track scanning radiometer with a wide field-of-view, providing a complete global coverage of the Earth in less than 2 days. Both Terra and Aqua MODIS went through extensive pre-launch calibration and characterization at various levels. In orbit, the calibration and characterization tasks are performed using its on-board calibrators （OBCs） that include a solar diffuser （SD） and a solar diffuser stability monitor （SDSM）, a v-grooved flat panel blackbody （BB）, and a spectro-radiometric calibration assembly （SRCA）. In this paper, we present an overview of MODIS calibration and characterization activities, methodologies, and lessons learned from pre-launch characterization and in-orbit operation. Key issues discussed in this paper include in-orbit efforts of monitoring the noise characteristics of the detectors, tracking the solar diffuser and optics degradations, and updating the sensor＇s response versus scan angle. The experiences and lessons learned through MODIS have played and will continue to play major roles in the design and characterization of future sensors.展开更多
Recent studies have explored the relationship between aerosol optical depth (AOD) measurements by satellite sensors and concentrations of particulate matter with aerodynamic diameters less than 2.5 μm (PM2.5). Howeve...Recent studies have explored the relationship between aerosol optical depth (AOD) measurements by satellite sensors and concentrations of particulate matter with aerodynamic diameters less than 2.5 μm (PM2.5). However, relatively little is known about spatial and temporal patterns in this relationship across the contiguous United States. In this study, we investigated the relationship between US Environmental Protection Agency estimates of PM2.5 concentrations and Moderate Resolution Imaging Spectroradiometer (MODIS) AOD measurements provided by two NASA satellites (Terra and Aqua) across the contiguous United States during 2005. We found that the combined use of both satellite sensors provided more AOD coverage than the use of either satellite sensor alone, that the correlation between AOD measurements and PM2.5 concentrations varied substantially by geographic location, and that this correlation was stronger in the summer and fall than that in the winter and spring.展开更多
Across the Arctic changes in active layer, melting of glaciers and ground ice, thawing of permafrost and sequestration changes of carbon storage are driven in part by variations of land surface heat absorption, conduc...Across the Arctic changes in active layer, melting of glaciers and ground ice, thawing of permafrost and sequestration changes of carbon storage are driven in part by variations of land surface heat absorption, conduction and re-radiation relative to solar irradiance. We investigate Arctic land-surface temperature changes and regional variations derived by the MODIS sensors on NASA Aqua and Terra from March 2000 through July 2012. Over this decadal period we detect increase in the number of days with daytime land-surface temperature above 0℃. There are indications of increasing trends of land-surface temperature change. Regional variations of the changes in land-surface temperature likely arise due to surface material types and topography relative to the daytime variation of solar irradiance.展开更多
This study compares the aerosol optical depth (AOD) Level 2 Collection 5 products from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) with ground-based measurements from a Microtops II sun p...This study compares the aerosol optical depth (AOD) Level 2 Collection 5 products from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) with ground-based measurements from a Microtops II sun photometer over Sanya (18.23°N,109.52°E),a tropical coastal site in China,from July 2005 to June 2006.The results indicate that the Terra and Aqua MODIS AOD retrievals at 550 nm have good correlations with the measurements from the Microtops II sun photometer.The correlation coefficients for the linear regression fits (R2) are 0.83 for Terra and 0.78 for Aqua,and the regressed intercepts are near zero (0.005 for Terra,0.009 for Aqua).However,the Terra and Aqua MODIS are found to consistently underestimate AOD with respect to the Microtops II sun photometer,with slope values of 0.805 (Terra) and 0.767 (Aqua).The comparison of the monthly mean AOD indicates that for each month,the Terra and Aqua MODIS retrievals are matched with corresponding Microtops measurements but are systematically less than those of the Microtops.This validation study indicates that the Terra and Aqua MODIS AOD retrievals can adequately characterize the AOD distributions over the tropical coastal region of China,but further efforts to eliminate systematic errors are needed.展开更多
Clouds can influence climate through many complex interactions within the hydrological cycle. Due to the important effects of cloud cover on climate, it is essential to study its variability over certain geographical ...Clouds can influence climate through many complex interactions within the hydrological cycle. Due to the important effects of cloud cover on climate, it is essential to study its variability over certain geographical areas. This study provides a spatial and temporal distribution of sky conditions, cloudy, partly cloudy, and clear days, in Iran. Cloud fraction parameters were calculated based on the cloud product(collection 6_L2) obtained from the Moderate Resolution Imaging Spectroradiometer(MODIS) sensors on board the Terra(MOD06) and Aqua(MYD06) satellites. The cloud products were collected daily from January 1, 2003 to December 31, 2014(12 years) with a spatial resolution of 5 km × 5 km. First, the cloud fraction data were converted into a regular geographic coordinate network over Iran. Then, the estimations from both sensors were analyzed. Results revealed that the maximum annual frequency of cloudy days occurs along the southern shores of the Caspian Sea, while the minimum annual frequency occurs in southeast Iran. On average, the annual number of cloudy and clear-sky days was 88 and 256 d from MODIS Terra, as compared to 96 and 244 d from MODIS Aqua. Generally, cloudy and partly cloudy days decrease from north to south, and MODIS Aqua overestimates the cloudy and partly cloudy days compared to MODIS Terra.展开更多
着重介绍了宽通道红外遥感器对应通道间的交叉辐射定标光谱匹配方法,并以FY-2CIR1、IR2与Terra/Aqua MODIS 31、32通道为切入点,进行通道间的光谱匹配计算,获取了两通道的光谱匹配因子,为实现这两种传感器红外分裂窗通道的交叉定标奠定...着重介绍了宽通道红外遥感器对应通道间的交叉辐射定标光谱匹配方法,并以FY-2CIR1、IR2与Terra/Aqua MODIS 31、32通道为切入点,进行通道间的光谱匹配计算,获取了两通道的光谱匹配因子,为实现这两种传感器红外分裂窗通道的交叉定标奠定了基础。该方法可以很好地应用于各种类型卫星红外遥感器的对应通道间交叉定标光谱匹配,为实现不同类红外遥感数据的辐射归一化提供了重要的方法借鉴,为建立一致的全球红外遥感观测数据库奠定了基础。展开更多
文摘Arctic nighttime land-surface temperatures derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the NASA Terra and Aqua satellites are investigated. We use the local equator crossing times of 22:30 and 01:30, respectively, in the analysis of changes, trends and variations on the Arctic region and within 120° sectors. We show increases in the number of days above 0°C and significant increase trends over their decadal periods of March 2000 through 2010 (MODIS Terra) and July 2002 through 2012 (MODIS Aqua). The MODIS Aqua nighttime Arctic land-surface temperature change, +0.2°C ± 0.2°C with P-value of 0.01 indicates a reduction relative to the MODIS Terra nighttime Arctic land-surface temperature change, +1.8°C ± 0.3°C with P-value of 0.01. This reduction is a decadal non-stationary component of the Arctic land-surface temperature changes. The reduction is greatest, -1.3°C ± 0.2°C with P-value of 0.01 in the Eastern Russia— Western North American sector of the Arctic during the July 2002 through 2012.
文摘针对Aqua和Terra MODIS AOD数据利用线性回归算法拟合结果不够精确的问题,本文提出了二次多项式回归算法对其进行拟合,二次多项式是指这个多项式的项数超过1,且最高次方数为2。采用二次多项式回归和线性回归算法分别对2015年随机选择的一天和4—6月的AOD数据进行拟合,并将两种方法拟合的结果进行对比分析。研究结果显示,针对同一组Aqua和Terra MODIS AOD数据的拟合,二次多项式回归方法拟合得到的RMSE、MAE、R值比线性回归拟合方法得到的值精度都要高很多,说明二次多项式回归拟合方法在Aqua和Terra MODIS AOD数据的拟合方面优于线性回归方法的拟合,证明了二次多项式回归拟合方法适用于此方面的研究,而且能够提升Aqua和Terra MODIS AOD数据拟合结果的精度。
文摘利用TERRA和AQUA共同反演气溶胶光学厚度和地表反射率特征,对其原理及方法进行了详细的讨论。通过Terra和Aqua两颗卫星对同一地点的不同角度的观测,结合多个光学通道的信息,反演了北京地区光学厚度及地表反射率信息。反演的气溶胶光学厚度同地面观测的结果相比具有很好的一致性。同时,对地表反射率及气溶胶波长指数等也进行了讨论和对比,结果显示,对北京地区,MOD IS 1通道地表反射率和7通道地表反射率的比在0.66左右,3通道和7通道的比在0.28左右。相比于NASA暗背景全球反演算法中1、3通道和7通道的比为0.50和0.25的处理方法,反演得到的气溶胶光学厚度结果也较好。
文摘The Moderate Resolution Imaging Spectroradiometer （MODIS） is one of the key instruments for NASA＇s Earth Observing System （EOS）, currently operating on both the Terra and Aqua satellites. The MODIS is a major advance over the previous generation of sensors in terms of its spectral, spatial, and temporal resolutions. It has 36 spectral bands： 20 reflective solar bands （RSB） with center wavelengths from 0.41 to 2.1 μm and 16 thermal emissive bands （TEB） with center wavelengths from 3.7 to 14.4 μm, making observations at three spatial resolutions： 250 m （bands 1-2）, 500 m （bands 3-7）, and lkm （bands 8-36）. MODIS is a cross-track scanning radiometer with a wide field-of-view, providing a complete global coverage of the Earth in less than 2 days. Both Terra and Aqua MODIS went through extensive pre-launch calibration and characterization at various levels. In orbit, the calibration and characterization tasks are performed using its on-board calibrators （OBCs） that include a solar diffuser （SD） and a solar diffuser stability monitor （SDSM）, a v-grooved flat panel blackbody （BB）, and a spectro-radiometric calibration assembly （SRCA）. In this paper, we present an overview of MODIS calibration and characterization activities, methodologies, and lessons learned from pre-launch characterization and in-orbit operation. Key issues discussed in this paper include in-orbit efforts of monitoring the noise characteristics of the detectors, tracking the solar diffuser and optics degradations, and updating the sensor＇s response versus scan angle. The experiences and lessons learned through MODIS have played and will continue to play major roles in the design and characterization of future sensors.
文摘Recent studies have explored the relationship between aerosol optical depth (AOD) measurements by satellite sensors and concentrations of particulate matter with aerodynamic diameters less than 2.5 μm (PM2.5). However, relatively little is known about spatial and temporal patterns in this relationship across the contiguous United States. In this study, we investigated the relationship between US Environmental Protection Agency estimates of PM2.5 concentrations and Moderate Resolution Imaging Spectroradiometer (MODIS) AOD measurements provided by two NASA satellites (Terra and Aqua) across the contiguous United States during 2005. We found that the combined use of both satellite sensors provided more AOD coverage than the use of either satellite sensor alone, that the correlation between AOD measurements and PM2.5 concentrations varied substantially by geographic location, and that this correlation was stronger in the summer and fall than that in the winter and spring.
文摘Across the Arctic changes in active layer, melting of glaciers and ground ice, thawing of permafrost and sequestration changes of carbon storage are driven in part by variations of land surface heat absorption, conduction and re-radiation relative to solar irradiance. We investigate Arctic land-surface temperature changes and regional variations derived by the MODIS sensors on NASA Aqua and Terra from March 2000 through July 2012. Over this decadal period we detect increase in the number of days with daytime land-surface temperature above 0℃. There are indications of increasing trends of land-surface temperature change. Regional variations of the changes in land-surface temperature likely arise due to surface material types and topography relative to the daytime variation of solar irradiance.
基金supported by the National Basic Research Program of China (Grant No. 2006CB 403702)
文摘This study compares the aerosol optical depth (AOD) Level 2 Collection 5 products from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) with ground-based measurements from a Microtops II sun photometer over Sanya (18.23°N,109.52°E),a tropical coastal site in China,from July 2005 to June 2006.The results indicate that the Terra and Aqua MODIS AOD retrievals at 550 nm have good correlations with the measurements from the Microtops II sun photometer.The correlation coefficients for the linear regression fits (R2) are 0.83 for Terra and 0.78 for Aqua,and the regressed intercepts are near zero (0.005 for Terra,0.009 for Aqua).However,the Terra and Aqua MODIS are found to consistently underestimate AOD with respect to the Microtops II sun photometer,with slope values of 0.805 (Terra) and 0.767 (Aqua).The comparison of the monthly mean AOD indicates that for each month,the Terra and Aqua MODIS retrievals are matched with corresponding Microtops measurements but are systematically less than those of the Microtops.This validation study indicates that the Terra and Aqua MODIS AOD retrievals can adequately characterize the AOD distributions over the tropical coastal region of China,but further efforts to eliminate systematic errors are needed.
基金Under the auspices of Faculty of Geographical Science and Planning,University of Isfahan,Doctoral Climatology Project(No.168607/94)
文摘Clouds can influence climate through many complex interactions within the hydrological cycle. Due to the important effects of cloud cover on climate, it is essential to study its variability over certain geographical areas. This study provides a spatial and temporal distribution of sky conditions, cloudy, partly cloudy, and clear days, in Iran. Cloud fraction parameters were calculated based on the cloud product(collection 6_L2) obtained from the Moderate Resolution Imaging Spectroradiometer(MODIS) sensors on board the Terra(MOD06) and Aqua(MYD06) satellites. The cloud products were collected daily from January 1, 2003 to December 31, 2014(12 years) with a spatial resolution of 5 km × 5 km. First, the cloud fraction data were converted into a regular geographic coordinate network over Iran. Then, the estimations from both sensors were analyzed. Results revealed that the maximum annual frequency of cloudy days occurs along the southern shores of the Caspian Sea, while the minimum annual frequency occurs in southeast Iran. On average, the annual number of cloudy and clear-sky days was 88 and 256 d from MODIS Terra, as compared to 96 and 244 d from MODIS Aqua. Generally, cloudy and partly cloudy days decrease from north to south, and MODIS Aqua overestimates the cloudy and partly cloudy days compared to MODIS Terra.
文摘着重介绍了宽通道红外遥感器对应通道间的交叉辐射定标光谱匹配方法,并以FY-2CIR1、IR2与Terra/Aqua MODIS 31、32通道为切入点,进行通道间的光谱匹配计算,获取了两通道的光谱匹配因子,为实现这两种传感器红外分裂窗通道的交叉定标奠定了基础。该方法可以很好地应用于各种类型卫星红外遥感器的对应通道间交叉定标光谱匹配,为实现不同类红外遥感数据的辐射归一化提供了重要的方法借鉴,为建立一致的全球红外遥感观测数据库奠定了基础。
