Satellite observation of Brazil Current inshore thermal front in the SW South Atlantic: Space/time variability and sea surface temperatures     

João A. Lorenzzetti  Jose L. Stech  Wilson L. Mello Filho  Arcilan T. Assireu 《Continental Shelf Research》2009

A data set of 199 sea surface temperature maps derived from the Advanced Very High Resolution Radiometer for the period 2000–2002 was processed to derive the position of the surface inshore thermal front of the Brazil Current (BCIF) in the SE Brazilian coastal and oceanic area. After the derivation of the position of the BC front for each image, the ensemble of digital frontal vectors was processed using the algorithm of frontal density (FD). For each 5′×5′ cell in the domain the calculated FD provided an index expressing the presence and persistence of the front in the area or the probability of finding the front in the region. In the paper we present the results of the FD analysis to get a better view of the space and time variability of the BC front in the region. The highest values of FD were in general observed close to or at the shelf break zone (between 200 and 1000 m isobaths). From 20°S to 23°S there is a tendency of BCIF to be positioned over the outer shelf, inshore of the 200 m isobaths. SE of Cape Sao Tome and S of Cape Frio it was observed a bimodal spatial distribution of highest FD caused by the presence of two semi-permanent frontal eddies. After moving offshore near Cape Frio, the BCIF tends to return to the shelf break zone south of 24°S probably due to a potential vorticity conservation mechanism. The position of the highest FD values calculated for different seasons confirms previous studies in that BCIF is closer to the coast during the summer and furthest offshore in the winter. Statistical analysis of the SST data gave for the BCIF an average SST gradient of 0.31°C km⁻¹ with a standard deviation of 0.15°C km⁻¹. A mean frontal width of 6 km was inferred from the average SST gradient and typical temperatures near the front at both sides, at outer shelf and in the BC itself. A Weibull probability density function can be fitted to describe the BCIF SST gradients with scale factor c=0.3460°C km⁻¹ and shape factor k=2.1737. The BCIF SST gradient showed a seasonal variability with the smallest gradients in summer (~0.24 °C km⁻¹) and the highest in autumn (~0.33 °C km⁻¹). Using a three harmonic Fourier fit for the SST field near the BCIF, at the outer shelf and at interior of BC, it was possible to derive an analytical model for the time variability of the SST gradient of BCIF.  相似文献   

卫星反演积雪信息的研究进展   总被引：10，自引：0，他引：10  

吴杨  张佳华  徐海明  何金海 《气象》2007,33(6):3-10

综合分析了积雪信息反演的主要遥感信息源和提取方法。在光学遥感方面，应用较广的主要是改进型甚高分辨率扫描辐射仪（AVHRR）资料和中分辨率成像光谱仪（MODIS）资料；提取积雪信息大多是根据积雪在可见光波段的高反射率和近红外波段的低反射率，并通过建立回归模型反演积雪面积和深度。由于传感器的改进，MODIS卫星资料在空间分辨率、积雪反演算法等方面明显优于AVHRR资料。光学仪器受云层和大气的影响很大，由于云和积雪在可见光和近红外波段上都具有高反射率。并且由于云层的遮挡。云下的地表信息不能被光学遥感仪器所接收到。微波遥感方面，被动微波遥感仪如微波辐射计成像仪（SSM／I）、高级微波扫描辐射计（AMSR—E）等可以全天候穿过云层进行监测，具有光学仪器所没有的优势，并通过提取地表的亮温差，建立雪深反演模型得到积雪深度。被动微波传感器存在分辨率低。无法监测浅雪区信息等问题。另外影响地表微波亮温的因素很多，这些都在一定程度上影响了反演结果的精确度。主动微波遥感仪如合成孔径雷达、微波散射计等利用积雪与其它地物的后向散射系数的不同来识别积雪，但也同样存在分辨率低等问题。最后探讨了卫星反演积雪信息中仍然存在的问题和进一步发展的方向。  相似文献   

2004年秋季江苏省干旱遥感监测研究          下载免费PDF全文

曾燕  邱新法  徐萌  李亚春 《气象科学》2007,27(3):302-306

2004年秋季,江苏省绝大多数地区降水明显比常年偏少,丘陵及高岗地区受旱严重。为了直观获得全省干旱空间分布情况,采用“表观热惯量指数”方法,结合2004年11月8日NOAA/AVHRR资料反演的地表反照率和昼夜地表温度,生成了江苏省“表观热惯量指数”空间分布图,获取了全省干旱空间分布情况,并在2004年11月9—14日全省出现2—6 d的降水过程后,利用2004年11月18日卫星资料,及时分析了全省旱情缓解情况,取的了很好的监测结果。  相似文献   

利用高程数据修正NOAA AVHRR轨道定位信息          下载免费PDF全文

郑照军刘瑞霞  刘玉洁 《应用气象学报》2007,18(4):417-426

在没有考虑高程数据的预处理方法得到的NOAA AVHRR资料中, 每条扫描线数据中的51点经纬度定位信息常常有误差, 尤其是在海拔较高、距卫星星下点较远的定位点, 其定位信息与实际差别很大。针对这种情况, 该文描述了一种引入高程数据并结合51点定位信息对2048个扫描点定位进行快速、简易的订正方法, 可有效地修正AVHRR资料预处理未考虑高程信息引起的经纬度定位偏差, 以便于对分辨率和定位精度要求不高的用户更好地使用AVHRR数据。  相似文献   

M变换在NOAA/AVHRR数据变化检测中的应用     

朱攀  廖明生  杨杰  刘良明 《武汉大学学报(信息科学版)》2000,25(2)

将基于典型相关分析的正交变换的基础理论用于NOAA/AVHRR数据的多元变化检测 ,对具体实施步骤进行了深入的探讨 ,并对部分中间结果进行了分析。实验表明 ,该方法应用于NOAA/AVHRR数据的多元变化检测具有明显的优势 ,克服了传统方法存在的缺陷 ,具有良好的应用前景。  相似文献   

过去21a中国西北植被覆盖动态监测与模拟   总被引：70，自引：3，他引：67  

马明国  董立新  王雪梅 《冰川冻土》2003,25(2):232-236

利用1981至2001年8kmAVHRR数据,采用均值法、差值法和一元线性回归模拟法,分析西北植被年内变化、年际变化特征,并模拟近21aNDVI最大化值的变化趋势线和NDVI增长幅度.统计结果表明,中国西北植被覆盖在7～8月达到年内最丰盛;近21a来植被覆盖存在普遍退化的趋势,且后10a变化幅度大于前10a变化幅度;在局部区域有植被改善的趋势,改善幅度小于退化幅度.模拟结果表明,植被改善的区域主要分布在新疆西部和北部地区.  相似文献   

Mesoscale Satellite Bioclimatology     

Bradley C. Rundquist  John A. Harrington  Jr.  Douglas G. Goodin 《The Professional geographer》2000,52(2):331-344

This paper examines the strength of relationships between the Normalized Difference Vegetation Index (NDVI) and climatic data, when examined at the mesoscale. Mean monthly AVHRR NDVI data for 1988‐1996 for the months of April through October for State of Kansas, its nine climatic divisions (CDs), and dominant land cover types within each CD were used. Corresponding climatic and water budget data were obtained or derived from National Climatic Data Center data. Temperature, precipitation, and NDVI deviations from normal were determined. Statistical analysis revealed significant relationships between NDVI and climatic variables, although strengths of the associations were modest. The highest correlation coefficient (r) for the state as a whole was 0.53, between NDVI and estimated actual evapotranspiration. When examined by climatic division or major land cover type, relationships between NDVI and a drought index were statistically significant in most cases and ranged from 0.30 to 0.56.  相似文献   

Satellite infrared remote sensing observation of surface circulation of the northeast South China Sea in winter     

Xu Jianping 《海洋学报(英文版)》2000,19(3):81-92

I~IOX \The investigation of physical oceanography in the South China Sea dates from early in the17th century and was carried out by scientists from many countries, including the United StateS,the United Kingdoms, Japan, .Russia and so on, but the survey area was rather limited at thattime and the data which were collected were still fragmentary. Since the 20th century, the investigation on the sleuth China Sea has made great progreSS not only in the scale of survey, but alsoin the depth …  相似文献   

星载红外数据应用于大型事故溢油   总被引：1，自引：0，他引：1  

杨娜  赵朝方 《地理空间信息》2006,4(2):63-65

使用NOAA卫星数据(AVHRR)同时对“阿提哥”号和“塔斯曼海”号溢油事件做出分析和研究。对出事海域的卫星数据进行了拉伸和彩色合成等图像增强处理,突出了影像上的油污特征;并根据其理化特性,设计算法实现了计算机对油污的自动判别;最后,估算了事故所溢油量,为事故后的调查、取证工作提供了良好依据。  相似文献