Development of an operational algorithm for estimating snow-cover fraction
K. V. Mitkari, M. K. Arora, V. D. Mishra, H. S. Gusain, N. K. Gupta, 2018. "Development of an operational algorithm for estimating snow-cover fraction", The Himalayan Cryosphere: Past and Present, N.C. Pant, R. Ravindra, D. Srivastava, L.G. Thompson
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This article describes an attempt to map snow cover accurately from other land covers using Moderate Resolution Imaging Spectrometer (MODIS) data of 500 m spatial resolution. The workflow includes reflectance modelling, computing snow-cover fraction (SCF) and establishing an empirical relationship between the SCF and normalized difference snow index (NDSI) to map snow cover at operational level. Regression relationships have been developed between the SCF derived from the linear mixture model (LMM) and snow obtained from the NDSI based on two criteria, namely: SCF greater than 0.0 and SCF greater than 0.1. The best regression equation has been selected by examining respective graph plots using statistical measures of mean absolute error, correlation coefficient, root mean square error (RMSE) and uncertainty analysis. The results have been validated against the actual SCF obtained from a high-resolution 15 m Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) visible and near infrared (VNIR) scene and covering a substantial range of snow cover of the same area. The selected regression model SCF = 0.25 + 0.35 × NDSI has been tested on other areas and validation efforts show that the pixel-level SCF relationship provides useful results as measured in independent tests against actual SCF obtained from ASTER scene.
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The Himalaya mountains contain not only one of the largest concentrations of ice outside the polar regions, but contribute to the hydrological requirements of large populations spread over seven nations. The exceptionally high elevations of this low-latitude cryosphere presents a natural laboratory and archives to study climate–tectonics interactions as well as regional v. global climate influences. The existing base-level data on the Himalayan cryosphere are highly variable. Several climate fluctuations occurred during the late Quaternary (MIS1–MIS5, especially the last c. 100 ka), which led to the evolution of the Himalayan landscape. Detailed studies of these archives, along with those of the present cryosphere and related hydrosphere, are essential for understanding the controls on present and future hydrology of the glacial-fed mountain rivers.
This volume, a follow-up of the XII International Symposium on Antarctic Earth Science, Goa (A SCAR symposium), provides new data from locales spread over the entire Himalaya region and from Tibet. It provides a glimpse of the late Quaternary cryosphere, as well as a discussion in the last section on sustainability in the context of geohazard mitigations as well as the hydrological budget.