基于WRF和一维雾模式的能见度集合预报的个例研究

利用WRF(weather research and forecasting)中尺度模式为一维辐射雾模式PAFOG提供扰动场,构建了一个有30个成员的辐射雾集合预报系统。对2007年12月13—14日南京地区一次典型辐射雾过程进行了预报效果分析,结果表明:该方法在地面能见度预报及雾层垂直结构预报上均好于实际探空作为初始场的单一预报结果;模式启动时刻对预报结果有较大影响,由于辐射雾多发生在夜间,且模式需要一定时间达到稳定,本方法中一维模式在14:00启动预报效果最好,集合预报成员与实测值的标准差平均值为0.516 km,集合平均值的平均预报绝对误差为0.287 km。     

UV-B辐射增强对河南省夏直播花生产量及品质的影响

在大田条件下,研究了模拟地表UV-B辐射增强对花生（开农49号）的产量及品质的影响.UV-B辐射设3个水平,即对照、增强20%和增强40%.结果表明：UV-B辐射增强能显著降低花生产量,产量下降的原因主要是由单位面积产量、株荚果数、百仁重减少造成的;花生品质受UV-B影响较为复杂,UV-B增强20%时,花生脂肪质量分数为51.02%,蛋白质质量分数为22.34%,油酸/亚油酸质量比为1.19,较对照组提高了0.02;UV-B增强40%时,花生脂肪质量分数为51.82%,蛋白质质量分数为22.56%,油酸/亚油酸质量比为1.28,较对照组提高了0.11.研究认为,UV-B辐射增强,不足以对花生的品质产生显著影响,这可能与设定的UV-B辐射强度、试验设计方案及花生的品种有关.     

Radiative forcing over China due to albedo change caused by land cover change during 1990-2010

Land cover change affects surface radiation budget and energy balance by changing surface albedo and further impacts the regional and global climate. In this article, high spatial and temporal resolution satellite products were used to analyze the driving mechanism for surface albedo change caused by land cover change during 1990-2010. In addition, the annual-scale radiative forcing caused by surface albedo changes in China's 50 ecological regions were calculated to reveal the biophysical mechanisms of land cover change affecting climate change at regional scale. Our results showed that the national land cover changes were mainly caused by land reclamation, grassland desertification and urbanization in past 20 years, which were almost induced by anthropogenic activities. Grassland and forest area decreased by 0.60% and 0.11%, respectively. The area of urban and farmland increased by 0.60% and 0.19%, respectively. The mean radiative forcing caused by land cover changes during 1990-2010 was 0.062 W/m2 in China, indicating a warming climate effect. However, spatial heterogeneity of radiative forcing was huge among different ecological regions. Farmland conversing to urban construction land, the main type of land cover change for the urban and suburban agricultural ecological region in Beijing-Tianjin-Tangshan region, caused an albedo reduction by 0.00456 and a maximum positive radiative forcing of 0.863 W/m2, which was presented as warming climate effects. Grassland and forest conversing to farmland, the main type of land cover change for the temperate humid agricultural and wetland ecological region in Sanjiang Plain, caused an albedo increase by 0.00152 and a maximum negative radiative forcing of 0.184 W/m2, implying cooling climate effects.     

A sun–crown–sensor model and adapted C-correction logic for topographic correction of high resolution forest imagery

Canopy shadowing mediated by topography is an important source of radiometric distortion on remote sensing images of rugged terrain. Topographic correction based on the sun–canopy–sensor (SCS) model significantly improved over those based on the sun–terrain–sensor (STS) model for surfaces with high forest canopy cover, because the SCS model considers and preserves the geotropic nature of trees. The SCS model accounts for sub-pixel canopy shadowing effects and normalizes the sunlit canopy area within a pixel. However, it does not account for mutual shadowing between neighboring pixels. Pixel-to-pixel shadowing is especially apparent for fine resolution satellite images in which individual tree crowns are resolved. This paper proposes a new topographic correction model: the sun–crown–sensor (SCnS) model based on high-resolution satellite imagery (IKONOS) and high-precision LiDAR digital elevation model. An improvement on the C-correction logic with a radiance partitioning method to address the effects of diffuse irradiance is also introduced (SCnS + C). In addition, we incorporate a weighting variable, based on pixel shadow fraction, on the direct and diffuse radiance portions to enhance the retrieval of at-sensor radiance and reflectance of highly shadowed tree pixels and form another variety of SCnS model (SCnS + W). Model evaluation with IKONOS test data showed that the new SCnS model outperformed the STS and SCS models in quantifying the correlation between terrain-regulated illumination factor and at-sensor radiance. Our adapted C-correction logic based on the sun–crown–sensor geometry and radiance partitioning better represented the general additive effects of diffuse radiation than C parameters derived from the STS or SCS models. The weighting factor W_t also significantly enhanced correction results by reducing within-class standard deviation and balancing the mean pixel radiance between sunlit and shaded slopes. We analyzed these improvements with model comparison on the red and near infrared bands. The advantages of SCnS + C and SCnS + W on both bands are expected to facilitate forest classification and change detection applications.     

净全辐射异常值的审核处理

针对近年来在省级质量控制数据R文件时净全辐射出现的问题,利用<地面自动站观测资料三级质量控制软件--省级软件>对净全辐射质量控制时数据异常原因进行举例分析,并采用人机交互方法对经质量控制后系统自动生成的疑误信息进行综合分析判断,同时结合有关规定和问题解答提出相应的处理方法,以确保净全辐射观测数据的真实、准确、可靠,进而为业务科研工作提供科学的、准确的数据.     

Landsat卫星遥感影像的大气校正方法研究

介绍了一种对Landsat卫星遥感影像逐像元进行大气校正模型,该模型基于MODTRAN大气辐射传输模型计算建立的查找表（look up table,LUT）,并结合暗元目标法（dark object method,DOM）,利用遥感影像自身的信息对遥感影像进行大气校正。以Landsat ETM＋遥感影像为例,介绍了算法流程,同时给出了大气校正前后的对比结果。结果表明,利用该模型进行的影像逐像元的大气校正,能够有效地降低大气中的大气分子、水汽、臭氧、气溶胶粒子等对卫星遥感影像造成的影响,获得更加精确的地物真实反射率,有利于遥感信息的进一步定量提取和专题解译。     

中国北方不同气候区晴天陆面过程区域特征差异

采用2008年7～9月份观测的中国干旱-半干旱区实验观测协同与集成研究资料,将我国北方干旱一半干旱区根据气候类型和地理位置划分为西北干旱区、黄土高原区和东北冷区三个区域,分析了干旱-半干旱区陆面热量平衡和辐射平衡日变化的区域差异.结果显示:不同气候区域的地表辐射和能量过程差异明显,而这种差异主要源于大气和土壤中可利用水...     

近50年中国东南地区地面太阳辐射变化对气温变化的影响

太阳是地球表层的最终能量来源,地面太阳辐射的变化会深刻影响地球的气候变化.本文利用中国东南地区14个气象台站1961～2008年总辐射和气温的同步观测资料,分析了近50年该地区地面太阳辐射的变化对气温变化的可能影响.结果表明,1961～1989年期间,该地区的地面太阳辐射显著减弱,所引起的气温下降超过了其他因素的增温效...     

受载煤体变形破裂微波辐射前兆规律的实验研究

对煤体在单轴压缩条件下的微波辐射效应和规律进行了实验研究.实验结果表明,受载煤体具有微波辐射效应,在煤体的变形破裂过程中伴随有6.6 GHz微波辐射信号产生,其前兆规律具有3种类型.基于电介质物理学对实验现象进行了解释.在单轴压缩实验中,煤体的亮温最大变化值为1.9～2.7K,这表明煤体的微波辐射特性明显优于红外辐射特...     

各向异性ATI介质剪切位错点源P波远场辐射

假设震源区为ATI介质,传播介质为全空间各向同性介质情况下,给出了剪切位错源P波远场辐射解析表达式,讨论了震源区各向异性对远场P波振幅和震源球的影响。结果表明,震源区裂隙密度,裂隙方位等参数的动态变化导致P波远场辐射花样也随之动态变化,同时也会造成非双力偶百分含量的动态变化。研究认为,在井中对中小地震的非双力偶机制进行...