应用NOAA/AVHRR资料监测水稻长势的研究

该文利用1992～1996年NOAA/AVHRR资料,结合实测的地面农作物生长发育农学参数,系统地分析了沈阳市水稻移栽至收获整个本田期间遥感归一化植被指数（NDVI）的变化规律,进而达到对沈阳市水稻长势遥感动态监测的目的。     

Automatic searching of control point in NOAA AVHRR image

This paper discusses the approaches for automatical searching of control points in the NOAA AVHRR image on the basis of data rearrangement in the form of latitude and longitude grid. The vegetation index transformation and multi-level matching strategies have been proven effective and successful as the experiments show while the control point database is established.     

NOAA/AVHRR与EOS/MODIS遥感产品NDVI序列的对比及其校正

利用Terra、Aqua两颗卫星的MODIS资料、NOAA-16和17的AVHRR资料,通过对太阳和卫星天顶角及方位角等引起的大气效应订正、大气气溶胶等粒子的散射订正以及NOAA系列卫星信号的衰减订正,得到以上四颗卫星一系列的NDVI产品;对比分析了上午星Terra和NOAA-17,下午星Aqua和NOAA-16两组不同卫星传感器NDVI的差异及其与光谱响应函数的关系。结果表明,Terra和Aqua卫星NDVI随卫星观测角度的不同差异较大,平均NDVI是一种更适合的MODIS/NDVI产品算法,它代表了观测角为±30°之间的NDVI值的分布,在大气和角度的订正基础上,本研究采用了三阶多项式再次订正了观测角引起的NDVI变化;NOAA-16和17所获得的NDVI值较MODIS得到的NDVI值小很多,以MODIS的NDVI产品为标准,应用光谱响应函数将NOAA系列NDVI进行归一化处理,所得的结果基本与MODIS所得的NDVI相当;该方法基本能实现NDVI产品序列的延伸,其资料序列有时空可比性。     

基于MODIS冬小麦长势监测研究

本文在对比分析MODIS NDVI与AVHRR NDVI的系统误差基础上,以MODIS/AVHRR卫星资料、地面农情观测资料为主要数据源,开发出淮北平原冬小麦长势监测旬、月MODIS NDVI比较模型和MODIS NDVI半定量监测指标模型,该模型在2005年检验应用中得到与实际较一致结果。     

近岸流系与长江入海悬浮泥沙输移扩散

通过两年较完整的序列 NOAA/AVHRR 数据和实测含沙量资料,利用考虑近岸Ⅱ类水体大气校正的泥沙定量反演算法,获得了较高精度的河口高浓度泥沙遥感反演模式;利用泥沙浓度分级图和反映流系特征的温度图象,系统分析了长江口悬浮泥沙扩散途径、范围及其与近岸流系的关系。影响长江入海悬浮泥沙扩散的近岸流系主要包括台湾暖流、黄海混合水、苏北沿岸流及浙江沿岸流等。冬季,近岸流系比较稳定,其配置状况在一定程度上影响着苏北沿岸泥沙流向长江口的扩散,并制约着入海悬浮泥沙的扩散途径;洪季,长江入海径流量是影响悬浮泥沙扩散的重要因子。同时,长江冲淡水、浙江沿岸流共同形成的冷水区与台湾暖流水之间锋面的强度,也对悬浮泥沙和冲淡水的扩散方向和范围有重要影响;春、秋两季入海悬浮泥沙的扩散型式分别向夏、冬季的分布格局过渡。此外,风应力显著影响着浑水区的扩散方向和范围。风浪掀沙引起的河口泥沙再悬浮,可使近岸泥沙扩散范围增大。     

A simulation study on the eco-environmental effects of 3N Shelterbelt in North China

Based on the Global Land Cover Characteristics Database (GLCCD) generated by the U.S. Geological Survey (USGS) and University of Nebraska-Lincoln (UNL), a new land cover dataset within a domain of 14.1–49.6°N, 84.6–140.5°E is extracted. This dataset is used to identify the achievements of constructing 3N (Northeast, North and Northwest of China) Shelterbelt in North China and to update the lower boundary conditions of the mesoscale model (MM5), a widely used mesoscale meteorological model. The model is then used to simulate the regional climate effects of the 3N Shelterbelt, the largest forestation engineering in the world. The simulation shows that the construction of the 3N Shelterbelt and the corresponding land use and land cover (LULC) variations in China have changed the roughness length in the cited model domain significantly. Consequently, the surface layer wind speed, air temperature, humidity, and the precipitation are all changed. As compared with the control run without the 3N Shelterbelt, the regional climate in North China is improved shown by the decreased wind speed, increased air humidity and precipitation. The paper also stresses that, in meteorological or climatic simulations, the lower boundary conditions related to the land cover has to be updated frequently by the satellite observed database since the LULC vary fast due to the increasing world population and human activities, this is especially true in developing countries like China.     

Modelling snowpack surface temperature in the Canadian Prairies using simplified heat flow models

Three practical schemes for computing the snow surface temperature T_s, i.e. the force–restore method (FRM), the surface conductance method (SCM), and the Kondo and Yamazaki method (KYM), were assessed with respect to T_s retrieved from cloud‐free, NOAA‐AVHRR satellite data for three land‐cover types of the Paddle River basin of central Alberta. In terms of R², the mean T_s, the t‐test and F‐test, the FRM generally simulated more accurate T_s than the SCM and KYM. The bias in simulated T_s is usually within several degrees Celsius of the NOAA‐AVHRR T_s for both the calibration and validation periods, but larger errors are encountered occasionally, especially when T_s is substantially above 0 °C. Results show that the simulated T_s of the FRM is more consistent than that of the SCM, which in turn was more consistent than that of the KYM. This is partly because the FRM considers two aspects of heat conduction into snow, a stationary‐mean diurnal (sinusoidal) temperature variation at the surface coupled to a near steady‐state ground heat flux, whereas the SCM assumes a near steady‐state, simple heat conduction, and other simplifying assumptions, and the KYM does not balance the snowpack heat fluxes by assuming the snowpack having a vertical temperature profile that is linear. Copyright © 2005 John Wiley & Sons, Ltd.     

Mechanisms controlling the intra-annual mesoscale variability of SST and SPM in the southern North Sea

Thermal and optical remote sensing data were used to investigate the spatial and temporal distribution of sea surface temperature (SST) and of suspended particulate matter (SPM) in the southern North Sea. Monthly SST composites showed pronounced seasonal warming of the southern North Sea and delineated the English coastal and continental coastal waters. The East-Anglia Plume is the dominant feature of the English coastal waters in the winter and autumn SPM composites, and the Rhine region of freshwater influence (ROFI), including the Flemish Banks, is the dominant feature of the continental waters. These mesoscale spatial structures are also influenced by the evolution of fronts, such as the seasonal front separating well-mixed water in the southern Bight, from the seasonally stratified central North Sea waters. A harmonic analysis of the SST and SPM images showed pronounced seasonal variability, as well as spring-neap variations in the level of tidal mixing in the East Anglia Plume, the Rhine ROFI and central North Sea. The harmonic analysis indicates the important role played by the local meteorology and tides in governing the SST and near-surface SPM concentrations in the southern North Sea. In the summer, thermal stratification affects the visibility of SPM to satellite sensors in the waters to the north of the Flamborough and Frisian Fronts. Haline stratification plays an important role in the visibility of SPM in the Rhine ROFI throughout the year. When stratified, both regions typically exhibit low surface SPM values. A numerical model study, together with the harmonic analysis, highlights the importance of tides and waves in controlling the stratification in the southern North Sea and hence the visibility of SPM.     

利用AVHRR数据反演陆地气溶胶光学厚度

开发AVHRR可见光通道反演陆地气溶胶光学厚度 (AOD) 的算法对于研究长时间序列AOD的变化有重要意义。AVHRR由于缺少2.1 μm通道而不能采用MODIS的暗背景算法,该文利用背景合成算法进行陆地AOD反演。背景合成算法是指假设一段时间内地表反射率变化不大且会出现相对清洁大气, 采用最小值合成即可得到地表反射率,再通过辐射传输模式6S制作的查算表查算得到AOD的反演结果。将此算法应用到2009年AVHRR中国部分陆地区域 (15°~45°N,75°~135°E) 得到AOD的时空分布,将反演结果与同期Aqua/MODIS的MOD04 AOD产品进行对比分析表明,华北和华东地区的反演效果较好,西北地区结果较差。以长江三角洲地区为例可知,AVHRR AOD产品与MODIS AOD产品以及AERONET观测的AOD相比相关系数基本在0.6以上,从时间变化规律来看,AVHRR AOD和MODIS AOD产品年变化趋势具有很好的一致性。该文为建立长时间序列AVHRR AOD数据集提供了一个较为可行的方法。     

NOAA18/AVHRR与FY-3A/VIRR的OLR产品一致性和差异性分析

卫星的射出长波辐射OLR(Outgoing Long-wave Radiation)数据具有不同程度的误差。为满足业务和科研工作的需要,对国产卫星FY-3 A/VIRR的OLR产品与其他同类卫星产品进行一致性和差异性分析是非常必要的。采用风云三号A星(FY-3A)扫描辐射计(VIRR)的OLR日平均产品作为被检验数据,美国大气海洋局NOAA18卫星上搭载的甚高分辨率扫描辐射计(AVHRR)OLR日平均产品作为检验源数据,使用相关系数、平均偏差、均方根误差、相对误差等检验方法,对两种产品进行一致性和差异性分析。结果表明,两种OLR资料大部分相关系数较大,平均偏差、均方根误差和相对误差较小,个别资料相关系数较小,平均偏差、均方根误差和相对误差较大。如2010年4月23日、7月13日和10月13日,相关系数、平均偏差、均方根误差、相对误差分别为(0.63,7 Wm^-2,31 Wm^-2,0.12)、(0.5,-5 Wm^-2,45 Wm^-2,0.125)和(0.3,-200 Wm^-2,225 Wm^-2,0.85)。这些偏差主要发生在高山和海洋地区,并且暖季相对冷季偏差较大,可能是由于高山、海洋地区和暖季较强的对流活动造成两种资料的对比结果存在一定的差异;此外,由于FY-3A为上午星,NOAA18为下午星,过境时间存在一定的差异,也给二者的对比结果带来一定的差异。