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Cloud detection is an essential preprocessing step for retrieving carbon dioxide from satellite observations of reflected sunlight.During the pre-launch study of the Chinese Carbon Dioxide Observation Satellite(TANSAT),a cloud-screening scheme was presented for the Cloud and Aerosol Polarization Imager(CAPI),which only performs measurements in five channels located in the visible to near-infrared regions of the spectrum.The scheme for CAPI,based on previous cloudscreening algorithms,defines a method to regroup individual threshold tests for each pixel in a scene according to the derived clear confidence level.This scheme is proven to be more effective for sensors with few channels.The work relies upon the radiance data from the Visible and Infrared Radiometer(VIRR)onboard the Chinese Feng Yun-3A Polar-orbiting Meteorological Satellite(FY-3A),which uses four wavebands similar to that of CAPI and can serve as a proxy for its measurements.The scheme has been applied to a number of the VIRR scenes over four target areas(desert,snow,ocean,forest)for all seasons.To assess the screening results,comparisons against the cloud-screening product from MODIS are made.The evaluation suggests that the proposed scheme inherits the advantages of schemes described in previous publications and shows improved cloud-screening results.A seasonal analysis reveals that this scheme provides better performance during warmer seasons,except for observations over oceans,where results are much better in colder seasons. 相似文献
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Hollow villages and rural restructuring in major rural regions of China: A case study of Yucheng City, Shandong Province 总被引：5，自引：1，他引：4
The agricultural land resources of China are relatively limited because of its large population.Therefore,balancing the land use for industrialization,urbanization,and food security is a big challenge.In recent years,rural hollowing in China has resulted in numerous of abandoned rural houses,and the areas with abandoned houses need to be restored into agricultural land with effective land consolidation techniques.This study used the method of benefit-cost analysis and the data collected through field surveys conducted in Yucheng City in the northwest of Shandong Province in March 2009,to examine how hollow villages (HVs) to be created and how to solve the problem.The qualitative and quantitative analyses indicate following results.1) The situation of HVs is becoming increasingly severe under rapid industrialization and urbanization in Yucheng City.2) Poor infrastructure in rural areas and incomplete urbanization are the main factors that have led to the rural hollowing in many major rural regions of China.3) In order to resolve the problem caused by HVs and increase agricultural land,reconstructing rural communities in the countryside is necessary.4) A new mechanism in the provision of compensation funds by developed regions to the villages in less-developed regions must be established. 相似文献
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本文提出了一种可业务化运行的海洋二号卫星散射计面元匹配方法,该算法主要用于将按时序排列的后向散射系数及相关参数投影到相应风矢量单元。面元匹配方法主要包括地面网格划分和后向散射系数观测结果重采样两个关键步骤。为简化计算,本文采用了以星下点轨迹为中心,以顺轨向及交轨向为坐标轴的地面网格划分方式。在重采样过程中,本文提出了一种“三点标定”重采样方法,利用观测脉冲的地面足印中心,星下点轨迹的起点,以及过地面足印中心做星下点轨迹垂线的交点,三点形成的直角三角形来计算每个后向散射系数观测结果在地面网格中对应的坐标。该直角三角形的两直角边分别对应观测脉冲在顺轨向和交轨向的坐标。同时,为减少由于星下点数据空间分布不连续引起的面元匹配误差,在采用三点标定法进行重采样之前,首先对星下点时空分布不连续的区域对时间插值,然后以时间为坐标,对星下点经度、纬度分别进行内插。对风矢量面元位置分布和风矢量反演精度等分析表明,本文提出的面元匹配算法,可在满足高质量海面风场反演的要求。 相似文献
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面元匹配是散射计海面风场反演的重要预处理步骤。为保障海洋二号卫星散射计(HSCAT)业务化海面风场反演,提出了一种可业务化运行的HSCAT面元匹配算法。HSCAT面元匹配算法包括地面网格划分和后向散射系数观测结果重采样两个关键部分。为简化计算,HSCAT采用以星下点轨迹为中心,以顺轨向及交轨向为坐标轴,分辨率为25 km×25 km的网格划分方式。重采样利用卫星星下点经纬度数据,对每个后向散射系数观测结果,以后向散射系数与各星下点球面距离的最小值为依据进行交轨向重采样,并以取得距离最小值所对应的星下点与该轨数据星下点起始位置的距离为依据进行顺轨向重采样,实现对后向散射系数观测结果的面元匹配。实验和对比结果表明,提出的面元匹配算法可对后向散射系数进行有效的重采样,风矢量面元的位置分布均匀,每个风矢量面元均有足够数量的独立观测后向散射系数,可在全球范围内满足高质量海面风场反演的要求。 相似文献
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