气候变化领域集成服务门户(CCPortal): On the need for a time- and location-dependent estimation of the NDSI threshold value for reducing existing uncertainties in snow cover maps at different scales

CCPortal

DOI	10.5194/tc-12-1629-2018
	On the need for a time- and location-dependent estimation of the NDSI threshold value for reducing existing uncertainties in snow cover maps at different scales
	Härer S.; Bernhardt M.; Siebers M.; Schulz K.
发表日期	2018
ISSN	19940416
卷号	12 期号:5
英文摘要	Knowledge of current snow cover extent is essential for characterizing energy and moisture fluxes at the Earth's surface. The snow-covered area (SCA) is often estimated by using optical satellite information in combination with the normalized-difference snow index (NDSI). The NDSI thereby uses a threshold for the definition if a satellite pixel is assumed to be snow covered or snow free. The spatiotemporal representativeness of the standard threshold of 0.4 is however questionable at the local scale. Here, we use local snow cover maps derived from ground-based photography to continuously calibrate the NDSI threshold values (NDSIthr) of Landsat satellite images at two European mountain sites of the period from 2010 to 2015. The Research Catchment Zugspitzplatt (RCZ, Germany) and Vernagtferner area (VF, Austria) are both located within a single Landsat scene. Nevertheless, the long-term analysis of the NDSIthr demonstrated that the NDSIthr at these sites are not correlated (r Combining double low line 0.17) and different than the standard threshold of 0.4. For further comparison, a dynamic and locally optimized NDSI threshold was used as well as another locally optimized literature threshold value (0.7). It was shown that large uncertainties in the prediction of the SCA of up to 24.1% exist in satellite snow cover maps in cases where the standard threshold of 0.4 is used, but a newly developed calibrated quadratic polynomial model which accounts for seasonal threshold dynamics can reduce this error. The model minimizes the SCA uncertainties at the calibration site VF by 50% in the evaluation period and was also able to improve the results at RCZ in a significant way. Additionally, a scaling experiment shows that the positive effect of a locally adapted threshold diminishes using a pixel size of 500m or larger, underlining the general applicability of the standard threshold at larger scales. © 2018 Author(s).
学科领域	calibration; estimation method; index method; Landsat; map; photography; pixel; satellite imagery; snow cover; spatiotemporal analysis; threshold; uncertainty analysis; Austria; Bavaria; Germany; Zugspitze Plateau
语种	英语
scopus关键词	calibration; estimation method; index method; Landsat; map; photography; pixel; satellite imagery; snow cover; spatiotemporal analysis; threshold; uncertainty analysis; Austria; Bavaria; Germany; Zugspitze Plateau
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/119154
作者单位	Institute of Water Management Hydrology and Hydraulic Engineering (IWHW), University of Natural Resources and Life Sciences (BOKU), Vienna, 1190, Austria; Commission for Glaciology, Bavarian Academy of Sciences and Humanities, Munich, 80539, Germany
推荐引用方式 GB/T 7714	Härer S.,Bernhardt M.,Siebers M.,et al. On the need for a time- and location-dependent estimation of the NDSI threshold value for reducing existing uncertainties in snow cover maps at different scales[J],2018,12(5).
APA	Härer S.,Bernhardt M.,Siebers M.,&Schulz K..(2018).On the need for a time- and location-dependent estimation of the NDSI threshold value for reducing existing uncertainties in snow cover maps at different scales.Cryosphere,12(5).
MLA	Härer S.,et al."On the need for a time- and location-dependent estimation of the NDSI threshold value for reducing existing uncertainties in snow cover maps at different scales".Cryosphere 12.5(2018).