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31.
Marlen D. Eve Kris M. Havstadt Walter G. Whitford Marlen D. Eve 《Environmental monitoring and assessment》1999,54(3):205-227
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. 相似文献
32.
Kisei Kinoshita Wang Ning Zhang Gang Andrew Tupper Naoko Iino Satoshi Hamada Satoshi Tsuchida 《Water, Air, & Soil Pollution: Focus》2005,5(3-6):89-100
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. 相似文献
33.
Satellite Remote Sensing of Terrestrial Net Primary Production for the Pan-Arctic Basin and Alaska 总被引:2,自引:0,他引:2
J. S. Kimball M. Zhao K. C. McDonald S. W. Running 《Mitigation and Adaptation Strategies for Global Change》2006,11(4):783-804
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. 相似文献
34.
35.
NOAA/AVHRR图像资料在大雾灾害监测中的应用 总被引:11,自引:0,他引:11
通过对NOAA(诺阿卫星 )资料 5个通道光谱特征的分析 ,阐述了利用NOAA/AVHRR(甚高分辨率辐射仪 )图像资料监测大雾灾害的基本原理和方法 ,初步探索了适于监测大雾的通道组合和量化判读指标 ,揭示出综合利用近红外 3通道与 4、5通道资料实施对雾监测 ,可取得比较好的效果 ,并对 2 0 0 3 0 1 12~ 13大雾的监测过程个例进行了分析。研究结果表明 ,卫星遥感技术在大雾灾害的监测方面具有宏观、快速、直观、信息源可靠且成本低等优点 ,是其它任何常规监测手段无法替代的。 相似文献
36.
根据AVHRRSST探讨中国北部海域冬季环流演变 总被引:2,自引:0,他引:2
收集了中国东部陆架海北部2000年8月至2001年12月的NOAA/AVHRR数据,通过SST换算,对北黄海和渤海的温度场分布以及冬季流场的月变化进行了分析.黄海暖流进入渤海后的余脉分成两个分支:向西的渤海中心支和向北的辽东湾支.渤海中心支向西运行有两个分叉:辽东湾叉和渤海湾叉.冬季黄海暖流较强,由于北风或东北风的影响,渤海中心支和辽东湾支经历了同存-消弱-加强-同存等阶段.辽东湾南下沿岸流增强,渤海中心支暖流减弱,黄海沿岸流随之增强.这些暖流和沿岸流构成了渤海的四个环流.在黄海,黄海暖流与黄海沿岸流、辽南沿岸流、西朝鲜沿岸流组成了三个环流. 相似文献