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A New Approach to the On-Orbit Evaluation of Point Spread Function of Thermal Infrared Images With Applications to FY-2 Satellite Products

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A New Approach to the On-Orbit Evaluation of Point Spread Fu...

作者： Qiang Guo,Changjun Yang,and Caiying Wei the national Satellite meteorological center,china meteorological administration,beijing 100081,china,the Key Laboratory of Radiometric Calibration and Validation for Environmental Satellite,china meteorological administration,beijing 100081,china

Spatial characteristics of thermal infrared(TIR) images are generally described by image-derived point spread function(IDPSF) for sampled imaging *** investigators working on IDPSF on-orbit evaluation focus on visible and near-infrared images and pay little attention on TIR ones,the reason of which lies on the fact that the assumption of an observed target with an ideal step profile is not suitable for TIR band. A new approach for TIR images is proposed here based on a more common slope-profile model,where the transition features, i.e.,the sample number(N) and the beginning position of slope interval,are extracted from the observed *** results show that the estimation performance will be increased, with lower noise level as well as higher system modulation transfer function value at half of normalized spatial frequency(MTF) or smaller *** a good performance system with noise squared-root variance(SRV) no more than 1.0 count and MTF between 0.3 and 0.4,the relative error between simulated and estimated MTF\s is less than 20%.The IDPSF of FY-2C satellite TIR band is estimated,and the derived MTF0.5 is properly close to on-ground testing *** image quality of FY-2C TIR band has been improved by using Wiener filtering and the estimated IDPSF,which eventually benefits the cloud detection product with more detectable low fractus and increased detection accuracy by about 1%in *** a step-profile target as a special case of this model,the proposed approach is also suitable for visible and near-infrared images.

关键词： Index Terms—Infrared imaging optical image processing optical transfer functions.

The characteristics of atmospheric CO_2 concentration variation of four national background stations in china

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Science china Earth Sciences 2009年第11期52卷 1857-1863页

作者： LIU LiXin, ZHOU LingXi, ZHANG XiaoChun, WEN Min, ZHANG Fang, YAO Bo & FANG ShuangXi Key Laboratory for Atmospheric Chemistry, Centre for Atmosphere Watch and Services (CAWAS), Chinese Academy of Meteoro- logical Sciences (CAMS), china meteorological administration (CMA), beijing 100081, china Key Laboratory for Atmospheric Chemistry Centre for Atmosphere Watch and Services (CAWAS) Chinese Academy of Meteorological Sciences (CAMS) China Meteorological Administration (CMA) Beijing China

Atmospheric carbon dioxide is an important kind of greenhouse gas which influences global temperature. Its concentration variation could indicate the distribution of human and natural activities in various regions. Through the non-dispersive infrared method, flask sampling of atmospheric CO2 concen- tration was measured weekly at four national background stations including Waliguan, Shangdianzi, Lin’an, and Longfengshan. Based on the data collected from September 2006 to August 2007, along with the Waliguan station’s experience on in situ observational data processing, the selection methods for sampling data through the atmospheric background CO2 concentration analysis were preliminarily discussed. On the basis of this result, the variation features of the four typical regions’ atmospheric background CO2 concentration was analyzed for the first time. The results show that the atmospheric CO2 concentration at Waliguan, Shangdianzi, Lin’an, and Longfengshan is 383.5, 385.9, 387.8, and 384.3 ppm, respectively. During the research period, CO2 concentration at the Waliguan station changed slightly. However, the CO2 concentration changed sharply at the Shangdianzi and the Lin’an stations due to the great influence of human activities in the Jingjinji and the Changjiang Delta economic zones, and changed regularly with seasons at Longfengshan station under dual influences of human activities and plant photosynthesis. The results from this study can lay the foundation for more profound studies on atmospheric CO2 concentration level of different areas in china, and could be used to improve the understanding of carbon source and sink distribution.

关键词： atmospheric CO2 flask sampling background data selection CO2 concentration regional difference

The relationship between spatial extent and duration of severe droughts in china over the last 50 years

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The relationship between spatial extent and duration of seve...

2010 Second IITA International Conference on Geoscience and Remote Sensing (IITA-GRS 2010)

作者： ZHANG Da-quan College of Atmospheric Sciences Lanzhou University Lanzhou china 730000FENG Guo-lin Laboratory for climate Studies national climate center china meteorological administration beijing china 100081

Correlation between spatial extent and duration of severe droughts process and its statistical law is analyzed using Palmer Drought Severity Index （PDSI） through a newly developed system of drought process monitoring. Results indicate that during the period from late 1990s to early 2000s,the percentage of severe drought （PDSI＜-3.0） in china is unprecedented since 1960 under the background of global warming and the variation of the distributions of droughts coverage areas in different seasons is uneven. The distribution of spatial extent and durations of severe droughts follows a power-law,e.g. the spatial-temporal characteristics of severe droughts is independent to their scaling,namely,being scale free. In general the area of severe droughts is correlated closely with its duration,while the deviations of the linear fit from its correlation is also high.

关键词： drought duration distribution power-law

Effect of non-spherical dust aerosol on its direct radiative forcing

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Effect of non-spherical dust aerosol on its direct radiative...

强化科技基础推进气象现代化——第29届中国气象学会年会

作者： Zhili Wang a,Hua Zhang b,Xianwen Jing a,b,Xiaodong Wei c a Chinese Academy of meteorological Sciences,beijing 100081,china b Laboratory for climate Studies,national climate center,china meteorological administration,beijing 100081,china c meteorological center,East china Bureau of Air Control,Shanghai 201702,china

The optical properties of spherical and non-spherical dust aerosols are calculated using the Lorenz-Mie theory and the combination of T-matrix method and an improved geometric optics *** resulting optical properties are then applied in an interactive system that coupled a general circulation model with an aerosol model to quantitatively analyze the effect of non-spherical dust aerosol on its direct radiative forcing(DRF).Our results show that the maximum difference in dust instantaneous radiative forcing(IRF) between spherical and non-spherical particles is 0.27 W m-2 at the top of the atmosphere(TOA) and appears over the Sahara Desert due to enhanced absorption of solar radiation by non-spherical *** global annual means of shortwave(longwave) IRFs due to spherical and non-spherical dust aerosols at the TOA for all sky are-0.62(0.074) W m-2 and-0.61(0.073) W m-2,respectively,and the corresponding values for clear sky are-1.16(0.092) W m-2 and-1.14(0.093) W m-2,which indicates that the non-spherical effect of dust has almost no effect on their global annual mean ***,non-spherical dust displays more evident influences than above on its atmospheric-and land-temperature adjusted radiative forcing(ARF) at the TOA over the Saharan Desert,West Asia,and northern china,with an approximate maximum increase of 3.0 and decrease of 0.5 W *** global annual means of shortwave(longwave) ARFs due to spherical and non-spherical dust aerosols are-0.55(0.052) W m-2 and-0.48(0.049) W m-2 at the TOA for all sky,respectively,and the corresponding values for clear sky are-1.07(0.066) W m-2 and-0.95(0.062) W *** ARFs of dust become much weaker than their corresponding *** absolute values of annual mean ARF for non-spherical dust are approximately 13%(11.2%) and 6%(6%) less than those of spherical dust for the shortwave and longwave for all sky(clear sky),*** results indicate that the non-spherical effect of dust can reduce their ARFs more obvio

关键词： Dust Spherical/Non-spherical Particles IRF ARF

An improvement on summer regional climate simulation over East china: importance of data assimilation of soil moisture

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An improvement on summer regional climate simulation over Ea...

第七届全国优秀青年气象科技工作者学术研讨会

作者： HU YaMin1, 2, DING YiHui3 & LIAO Fei2 1 Guangdong climate center, Guangzhou 510080, china 2 Institute of Tropical and Marine Meteorology, china meteorological administration, Guangzhou 510080, china 3 national climate center, china meteorological administration, beijing 100081, china

The Newtonian relaxation is used to assimilate data from the Second Global Soil Wetness Project (GSWP2) into the initial field for soil moisture in a regional climate model (i. e., BCCegCM 1.0, hereinafter called RegCM). The results show that different nudging parameters can improve the simulation of the air temperature and the precipitation to some extent in summertime sea-son over East china. When the nudging intensity is 0.5 and nudging duration is 5 days, the result is desirable. Introducing the data assimilation of soil moisture into RegCM, the amelioration is not only in the spatial distribution pattern but also in the mag-nitude of the temperature and the precipitation. More specifically, the assimilation experiments have corrected the systematical cold bias of the air temperature and the precipitation on the low side, which is much closer to the observation compared with the control experiment. On the whole, the assimilation experiments shed light on the fact that the simulated bias in the original RegCM may be affected by the description of soil moisture in the land surface process. Therefore, the effect of soil moisture in RegCM should be paid more attention in the future.

关键词： soil moisture Newtonian relaxation data assimilation regional climate simulation

Adaptation strategy for sea level rise in vulnerable areasalong china's coast

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Acta Oceanologica Sinica 2000年第4期19卷 1-16页

作者： Du Bilan, Zhang Jinwen (china Institute of Marine Affairs, State Oceanic administration, beijing 100860, china national Marine Data and Information Service, Tianjin 300171, china) china Institute of Marine Affairs State Oceanic Administration Beijing 100860 China

It can be seen from the calculation that the vulnerable area along china's coast in which the elevation is less than 5 m, is 143 900 km2, accounting for about 11. 3% of the total area of the 11 coastal provinces, municipalities and autonomous regions. These areas are threatened to varying extent by sea level rise. According to prediction, the relative sea level rise (including global sea level rise caused by climate change and local relative as level rise caused by vertical crust movement and ground subsidence) along china's coast will be 4～16 cm by the year 2030 with the optimum estimated value of 6～14cm. It will be 9～26 cm by the year 2050 with the optimum estimated value of 12-23 cm. And it will be 31-74 cm by the year 2100 with the optimum estimated value of 47～65 cm. The calcuation result shows that the percentage of the cost for up-grading (heightening and consolidating) sea dykes/walls in adaptation strategy in the losses of submerged areas varies from area to area: 6. 9% in the Zhujiang (Pearl) River Deta, 1. 3% ～24. 6% in the Changjiang (Yangtze) River Delta, and 0. 9%～2. 0% in the Huanghe River Delta.

关键词： Adaptation strategy for sea level rise vulnerable areas along china's coast submerged areas

A three-dimensional variational ocean data assimilation system:Scheme and preliminary results

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Science china Earth Sciences 2006年第11期49卷 1212-1222页

作者： ZHU Jiang1,2, ZHOU Guangqing1, YAN Changxiang1, FU Weiwei1 & YOU Xiaobao1,3 1. International center for climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, beijing 100029, china 2. Jiangsu Key Laboratory of meteorological Disaster, Nanjing University of Information Science and Technology, Nanjing 210044, china 3. beijing Institute of Applied Meteorology, beijing 100029, china International center for climate and Environment Sciences Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Jiangsu Key Laboratory of meteorological Disaster Nanjing University of Information Science and Technology Nanjing China beijing Institute of Applied Meteorology Beijing China

A new 3DVAR-based Ocean Variational Analysis System (OVALS) is developed. OVALS is capable of assimilating in situ sea water temperature and salinity observations and satellite altimetry data. As a component of OVALS, a new variational scheme is proposed to assimilate the sea surface height data. This scheme considers both the vertical correlation of background errors and the nonlinear temperature-salinity relationship which is derived from the generalization of the linear balance constraints to the nonlinear in the 3DVAR. By this scheme, the model temperature and salinity fields are directly adjusted from the altimetry data. Additionally, OVALS can assimilate the temperature and salinity profiles from the ARGO floats which have been implemented in recent years and some temperature and salinity data such as from expendable bathythermograph, moored ocean buoys, etc. A 21-year assimilation experiment is carried out by using OVALS and the Tropical Pacific circulation model. The results show that the assimilation system may effectively improve the estimations of temperature and salinity by assimilating all kinds of observations. Moreover, the root mean square errors of temperature and salinity in the upper depth less than 420 m reach 0.63℃ and 0.34 psu.

关键词： data assimilation, 3DVAR, sea surface height, ARGO floats.

Detection of the Kuroshio frontal instable processes (KFIP) in the East china Sea using the MODIS images

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Acta Oceanologica Sinica 2010年第6期29卷 35-43页

作者： JIA Yongjun ZHANG Jie national Satellite Ocean Application Service Beijing 100081 China First Institute of Oceanography State Oceanic Administration Qingdao 266061 China

The Kuroshio frontal instable processes （KFIP） in the East china Sea （ECS） not only have a great impact on the hydrologic characteristics,the pollutants drift,the distribution of seafloor sediment and the ships navigation of the ECS,but also are closely related to the climate changes of the coastal areas of the *** the frequency and area of occurrence of the KFIP have not been studied fully and *** of its high spatial and temporal resolution,MODIS data is a kind of very good data source for surveying and researching the KFIP in the *** aim of this study is to detect the KFIP in the ECS by using MODIS data,and to study the frequency and region of occurrence of the KFIP in the *** selection has coverage of level 2 data of MODIS SST and Kd490 ranging from July 1,2002 to June 30,2009 of the ECS when there was no cloud impact or *** using of the data,the minimum standard of the Kuroshio temperature fronts and the diffuse attenuation coefficient （Kd490） fronts of the ECS are *** on these standards and the curvature distinguish methods,the standard of curvature distinguish for the KFIP in the ECS are put *** making use of this standard,we study a total of 2073 satellite-derived images,and discover that as long as there is no cloud impact from January to May and October to December,the KFIP in the ECS are surely found in MODIS satellite *** June to September,the frequency of occurrence can also reach to 82.9% at ***,it is obtained that there are three source regions of these instability processes,namely,（26°N,121.5°E） nearby,（27°N,125°E） nearby and （30°N,128°E） *** differences of the characteristics of these instability processes which are generated in different regions are analyzed in the present study.

关键词： Kuroshio frontal instable processes frequency and region of occurrence East china Sea MODIS

A LAI Inversion Algorithm Based on Directional Reflectance

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A LAI Inversion Algorithm Based on Directional Reflectance

中国气象学会2004年年会

作者： Tang Shihao~(12) (1 national Satellite meteorological center, china meteorological administration, beijing 100081, china 2 Remote Sensing and GIS Research center, Department of Geography, beijing Normal University, beijing 100875, china)

＜正＞Leaf area index (LAD is an important ecological and environmental parameter. The current remote sensing inversion methods of leaf area index can mainly（?）e grouped into two classes: vegetation index based methods and remote sensing physical model based methods. In this paper, a new LAI retrieval method is developed. The algorithm borrows ideas from the principles and methods of ground LAI measurements, and adopts a new frame which differs from traditional remote sensing LAI inversion methods. First, the relationship between LAI and directional gap fraction is derived from the definition of LAI. Then, directional gap fraction is acquired from remote sensing bidirectional reflectance distribution function （BRDF） product. This acquisition is obtained by the use of a kernel driven model and a large scale directional gap fraction algorithm. At last, the large scale LAI is calculated through angle integrations. This algorithm has been applied to get LAI distribution of china in the middle of July, 2002. The ground data acquired from two field experiments conducted in Changbai Mountain and Qiiian Mountain, china, are used to validate the algorithm. In order to resolve the scale change problem between high resolution grouad observation and low resolution remote sensing data, two high resolution remote sensing images almost ha, ing the same resolutions with ground measurements are used as transitions. In order to proceed, we first bulid an empirical relationship between measured LAI and high resolution reflectance. Then, we get high resolu ion LAI distribution according to that relation. The LAI value of a low resolution pixel is calculated from the areal weighted sum of high resolution LAIs composing the low resolution pixel. Our results show that the algo（?）ithm has a high precision. Factors that may influence the precision of the algorithm are also discussed in this paper.

关键词： LAI MODIS BRDF ALBEDO Gap fraction