No abstract

The Thematic Mapper (TM) instruments onboard Landsats 4 and 5 provide high-quality imagery appropriate for many different applications, including land cover mapping, landscape ecology, and change detection. Precise calibration was considered to be critical to the success of the Landsat 7 mission and, thus, issues of calibration were given high priority during the development of the Enhanced Thematic Mapper Plus (ETM+). Data sets from the Landsat 5 TM are not routinely corrected for a number of radiometric and geometric artifacts, including memory effect, gain/bias, and interfocal plane misalignment. In the current investigation, the effects of correcting vs. not correcting these factors were investigated for several applications. Gain/bias calibrations were found to have a greater impact on most applications than did memory effect calibrations. Correcting interfocal plane offsets was found to have a moderate effect on applications. On June 2, 1999, Landsats 5 and 7 data were acquired nearly simultaneously over a study site in the Niobrara, NE area. Field radiometer data acquired at that site were used to facilitate crosscalibrations of Landsats 5 and 7 data. Current findings and results from previous investigations indicate that the internal calibrator of Landsat 5 TM tracked instrument gain well until 1988. After this, the internal calibrator diverged from the data derived from vicarious calibrations. Results from this study also indicate very good agreement between prelaunch measurements and vicarious calibration data for all Landsat 7 reflective bands except Band 4. Values are within about 3.5% of each other, except for Band 4, which differs by 10%. Coefficient of variation (CV) values derived from selected targets in the imagery were also analyzed. The Niobrara Landsat 7 imagery was found to have lower CV values than Landsat 5 data, implying that lower levels of noise characterize Landsat 7 data than current Landsat 5 data. It was also found that following radiometric normalization, the Normalized Difference Vegetation Index (NDVI) imagery and classification products of Landsats 5 and 7 were very similar. This implies that data from the two sensors can be used to measure and monitor the same landscape phenomena and that Landsats 5 and 7 data can be used interchangeably with proper caution. In addition, it was found that difference imagery produced using Landsat 7 ETM+ data are of excellent quality. D

Alpine glaciers directly and indirectly respond to climate and play a significant role in mountain geodynamics. Many glaciers around the world have been found to be retreating and downwasting, although these patterns are highly variable due to variations in local topography, regional climate and ice-flow dynamics. Unfortunately, limited information is available on glacier fluctuations in the Wakhan Pamir of Afghanistan, and no data exist from there in the World Glacier Monitoring Services (WGMS) database. Our general circulation model (GCM) climate simulations represent a double carbon-dioxide-loading scenario, and results suggest that glaciers in this region should be downwasting and retreating. Therefore, as part of the Global Land Ice Measurements from Space (GLIMS) project, we evaluated ASTER and Landsat MSS data to assess glacier fluctuations from 1976-2003, in the Wakhan Corridor of Afghanistan. We sampled 30 alpine valley, compound alpine valley or cirque-type glaciers of varying size and orientation. Results indicate that 28 glacier-terminus positions have retreated, and the largest average retreat rate was 36 m year −1 . Satellite image analysis reveals non-vegetated glacier forefields formed prior to 1976, as well as geomorphological evidence for apparent glacier-surface downwasting after 1976. Climatic conditions and glacier retreat have resulted in 6 Climatic Change (2009) 94:5-18 disconnection of tributary glaciers to their main trunk, the formation of high-altitude lakes, and an increased frequency and size of proglacial lakes. Collectively, these results suggest increased hazard potential in some basins and a negative regional mass balance.

The U.S. Environmental Protection Agency is charged with establishing standards and criteria for assessing lake water quality. It is, however, increasingly evident that a single set of national water quality standards that do not take into account regional hydrogeologic and ecological differences will not be viable as lakes clearly have different inherent capacities to meet such standards. We demonstrate a GIS‐based watershed classification strategy for identifying groups of Nebraska reservoirs that have similar potential capacity to attain a certain level of water quality standard. A preliminary cluster analysis of 78 reservoirs was performed to determine the potential number of Nebraska reservoir groups. Subsequently, a Classification Trees method was used to refine number of classes, describe the structure of reservoir watershed classes, and to develop a predictive model that relates watershed conditions to reservoir classes. Results suggest that Nebraska reservoirs can be represented by nine classes and that soil organic matter content in the watershed is the most important single variable for segregating the reservoirs. The cross‐validation prediction error rate of the Classification Tree model was 26.3%. Because all geospatial data used in this work are available nationally, the method could be adopted throughout the U.S. Hence, this GIS‐based watershed classification approach could provide water resources managers an effective decision‐support tool in managing reservoir water quality.

No abstract