Using NOAA AVHRR data to assess flood damage in China

The article used two NOAA-14 Advanced Very High ResolutionRadiometer (AVHRR) datasets to assess flood damage in the middleand lower reaches of China's Changjiang River (Yangtze River) in 1998. As the AVHRR is an optical sensor, it cannot penetratethe clouds that frequently cover the land during the flood season, and this technology is greatly limited in flood monitoring. However the widely used normalized difference vegetation index (NDVI) can be used to monitor flooding, sincewater has a much lower NDVI value than other surface features.Though many factors other than flooding (e.g. atmospheric conditions, different sun-target-satellite angles, and cloud) can change NDVI values, inundated areas can be distinguished fromother types of ground cover by changes in the NDVI value beforeand after the flood after eliminating the effects of other factors on NDVI. AVHRR data from 26 May and 22 August, 1998 wereselected to represent the ground conditions before and after flooding. After accurate geometric correction by collecting GCPs,and atmospheric and angular corrections by using the 6S code, NDVI values for both days and their differences were calculatedfor cloud-free pixels. The difference in the NDVI values betweenthese two times, together with the NDVI values and a land-use map, were used to identify inundated areas and to assess the arealost to the flood. The results show a total of 358 867 ha, with 207 556 ha of cultivated fields (paddy and non-irrigated field) inundated during the flood of 1998 in the middle and lower reaches of the Changjiang River Catchment; comparing with the reported total of 321 000 and 197 000 ha, respectively. The discrimination accuracy of this method was tested by comparing the results from two nearly simultaneous sets of remote-sensingdata (NOAA's AVHRR data from 10 September, 1998, and JERS-1 synthetic aperture radar (SAR) data from 11 September, 1998, with a lag of about 18.5 hr) over a representative flooded regionin the study area. The results showed that 67.26% of the total area identified as inundated using the NOAA data was also identified as inundated using the SAR data.     

Detection of Asian dust aerosols using meteorological satellite data and suspended particulate matter concentrations

The advection and dispersion of Asian dust events from China to the Pacific Ocean around Japan during 2000–2002 were investigated using the meteorological satellite data of NOAA/AVHRR and GMS-5/VISSR. Aerosol vapour index images, taking the brightness temperature difference between 11 and 12 μm, are very effective for monitoring the Asian dust phenomenon in the East Asia region, with their capacity for detection during the day or night. We discuss the dust events, focusing on the advection patterns shown in satellite images, which are classified into three types as ‘dry slot’, ‘high-pressure wedge’ and ‘travelling high’, based on synoptic patterns. The results are compared with suspended particulate matter concentrations measured at Japanese surface stations and with ground-based observations of Sakurajima volcano by a web camera system at Kagoshima in Kyushu, Japan. We found that the passage of cold fronts caused a rapid increase of suspended particulate matter (SPM) concentrations, which exceeded 100 μg m⁻³, and that deep low-pressure complexes strengthened the dust phenomenon. The ‘high-pressure wedge’ type is seen much more clearly in satellite images than the ‘travelling high’ type, but SPM concentrations and visibility were similar in both owing to the differences in the vertical distribution of the dust and in viewing conditions.     

华北植被的净初级生产力研究及其时空格局分析

在CASA模型的基础上,建立了利用NOAA/AVHRR 1B卫星资料和气象资料估算植被净初级生产力(NPP)的技术方法,该方法有3个特色:直接利用NOAA/AVHRR 1B卫星数据,不需要经过大气校正和方向反射率校正来实现NPP估算;考虑了植被覆盖类型对光能利用率的影响;考虑了植被反照率在计算净辐射中的差异。利用该方法对2007年华北地区的NPP模拟结果表明:2007年华北地区植被的年总NPP为3.68×1014gC/a,各省总的NPP贡献率依次为:内蒙古64%、山西20%、河北13%、北京2%和天津1%,各季的贡献率大小依次为:夏季67%,秋季17%、春季15%,冬季1%。不同植被类型年NPP分别为:森林灌丛为271~560 gC/m2.a,草原为97~278 gC/m2.a,农田为363~376 gC/m2.a,建筑居民地为216 gC/m2.a,荒漠裸地为14 gC/m2.a。受物候和气候因素影响,不同植被类型NPP具有不同的年变化。     

Remote sensing technology and land use analysis in food security assessment

ABSTRACT

Climate change and a rapidly growing human population have put ever greater strains on the global food system. Although the number of food insecure people in the world has reached a record low, changing land use and climate variability will threaten our ability to maintain this progress. Profound changes in the structure of economies around the world have affected agricultural production and how food is delivered to the consumer. This paper explores connections between land use, environmental change and food availability, access, and utilization. Each of these elements of food security has vulnerabilities to changing environmental conditions and land use that can be explored using satellite remote sensing observations. Technology is a key way environmental changes can be quantified and used in food security assessment.     

AVHRR遥感数据在海表赤潮细胞数探测中的应用

以1998年渤海赤潮过程中的现场实测资料和同步的NOAA－14的AVHRR数据,以植被指数（NDVI）为基础,建立了渤海叉角藻赤潮生物细胞数遥感探测模型,该模型使用简便,可以有效地利用目前正在运行的气象卫星数据进行赤潮的业务化监测,直接获取赤潮浮游植物细胞数这个指标,确定赤潮的发生范围,赤潮面积以及赤潮生物分布的密集区,并计算细胞分裂速度以判定赤潮的生消状况,为赤潮灾害的应急防治工作提供依据。同时可以区分赤潮水体与其他如何流或排污口排放的泥沙或悬浮物,以消除这些物质对赤潮识别带来的影响。     

若尔盖草原NDVI的季节特点和变化规律

文章使用NOAA17/AVHRR数据,采用归一化差值植被指数(NDVI)模型,对2006年3月～2007年2月若尔盖及周边地区进行计算和分析得出,NDVI在7月最大,12月最小;结合降水量和气温的年变化,分析了NDVI的季节特点和变化规律的气候基础.     

Applying Satellite Imagery to Triage Assessment of Ecosystem Health

Considerable evidence documents that certain changes in vegetation and soils result in irreversibly degraded rangeland ecosystems. We used Advanced Very High Resolution Radiometer (AVHRR) imagery to develop calibration patterns of change in the Normalized Difference Vegetation Index (NDVI) over the growing season for selected sites for which we had ground data and historical data characterizing these sites as irreversibly degraded. We used the NDVI curves for these training sites to classify and map the irreversibly degraded rangelands in southern New Mexico. We composited images into four year blocks: 1988–1991, 1989–1992, and 1990–1993. The overlap in pixels classified as irreversibly degraded ranged from 42.6% to 84.3% in year block comparisons. Quantitative data on vegetation composition and cover were collected at 13 sites within a small portion of the study area. Wide coverage reconnaissance of boundaries between vegetation types was also conducted for comparisons with year block maps. The year block 1988–1991 provided the most accurate delineation of degraded areas. The rangelands of southern New Mexico experienced above average precipitation from 1990–1993. The above average precipitation resulted in spatially variable productivity of ephemeral weedy plants on the training sites and degraded rangelands which resulted in much smaller areas classified as irreversibly degraded. We selected imagery for a single year, 1989, which was characterized by the absence of spring annual plant production in order to eliminate the confounding effect of reflectance from annual weeds. That image analysis classified more than 20% of the rangelands as irreversibly degraded because areas with shrub-grass mosaic were included in the degraded classification. The single year image included more than double the area classified as irreversibly degraded by the year blocks. AVHRR imagery can be used to make triage assessments of irreversibly degraded rangeland but such assessment requires understanding productivity patterns and variability across the landscapes of the region and careful selection of the years from which imagery is chosen.     

Long-Term Observation of Asian Dust in Changchun and Kagoshima

Monitoring of Asian dust at two stations in Changchun, Jilin Province in northeast China, and Kagoshima, southwest Japan, is discussed. In Changchun, interval records were made with digital and video cameras from 18 March 2003. In Kagoshima, a web camera system to monitor volcanic clouds has been working since December 2000, which also provides data for studies of dust. A heavy dust episode on 11 November 2002, affecting both stations, was detected using 11 and 12 μm channels of NOAA/AVHRR. We observed dust in Changchun on 26 March, 7, 14–16 April, 1–2, 8, 10, 19 May, 8, 23 June, and 12 July in 2003. The observed images corresponded well to NOAA/AVHRR imagery and with 8.6, 11 and 12 μm Terra/MODIS results, although conditions were too cloudy for satellite verification in some cases.     

Satellite Remote Sensing of Terrestrial Net Primary Production for the Pan-Arctic Basin and Alaska

We applied a terrestrial net primary production (NPP) model driven by satellite remote sensing observations of vegetation properties and daily surface meteorology from a regional weather forecast model to assess NPP spatial and temporal variability for the pan-Arctic basin and Alaska from 1982 to 2000. Our results show a general decadal trend of increasing NPP for the region of approximately 2.7%, with respective higher (3.4%) and lower (2.2%) rates for North America and Eurasia. NPP is both spatially and temporally dynamic for the region, driven largely by differences in productivity rates among major biomes and temporal changes in photosynthetic canopy structure and spring and summer air temperatures. Mean annual NPP for boreal forests was approximately 3 times greater than for Arctic tundra on a unit area basis and accounted for approximately 55% of total annual carbon sequestration for the region. The timing of growing season onset inferred from regional network measurements of atmospheric CO₂ drawdown in spring was inversely proportional to annual NPP calculations. Our findings indicate that recent regional warming trends in spring and summer and associated advances in the growing season are stimulating net photosynthesis and annual carbon sequestration by vegetation at high latitudes, partially mitigating anthropogenic increases in atmospheric CO₂. These results also imply that regional sequestration and storage of atmospheric CO₂ is being altered, with potentially greater instability and acceleration of the carbon cycle at high latitudes.     

基于NOAA/AVHRR卫星资料的巢湖水华规律分析

以卫星遥感2002~2007年NOAA/AVHRR为信息源,统计这一时段内巢湖发生水华的资料,对水华的时空变化规律进行了分析.同时,结合相应的气象要素资料,对水华发生的气象条件进行分析.结果表明,巢湖水华的发生具有明显的时空规律,春、夏季多发,4,8月份的发生概率分别为19%和39%;西半湖多发,年均发生概率最大值均超过8%;气温、日照和风是影响巢湖水华的主要气象因子.