Derivation of high spatial resolution albedo from UAV digital imagery: application over the Greenland Ice Sheet

Ryan, J. C. et al. (2017) Derivation of high spatial resolution albedo from UAV digital imagery: application over the Greenland Ice Sheet. Frontiers in Earth Science, 5, 40. (doi: 10.3389/feart.2017.00040)

Abstract

Measurements of albedo are a prerequisite for modeling surface melt across the Earth's cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimeter resolution albedo products with accuracies of ±5% using consumer-grade digital camera and unmanned aerial vehicle (UAV) technologies. Our method comprises a workflow for processing, correcting and calibrating raw digital images using a white reference target, and upward and downward shortwave radiation measurements from broadband silicon pyranometers. We demonstrate the method with a set of UAV sorties over the western, K-sector of the Greenland Ice Sheet. The resulting albedo product, UAV10A1, covers 280 km2, at a resolution of 20 cm per pixel and has a root-mean-square difference of 3.7% compared to MOD10A1 and 4.9% compared to ground-based broadband pyranometer measurements. By continuously measuring downward solar irradiance, the technique overcomes previous limitations due to variable illumination conditions during and between surveys over glaciated terrain. The current miniaturization of multispectral sensors and incorporation of upward facing radiation sensors on UAV packages means that this technique could become increasingly common in field studies and used for a wide range of applications. These include the mapping of debris, dust, cryoconite and bioalbedo, and directly constraining surface energy balance models.

• Item Type: Articles
• Additional Information: Fieldwork was supported by Dark Snow Project crowd funding (http://www.darksnow.org/), a grant from the Leonardo DiCaprio Foundation and an Aberystwyth University Research Fund. JR was supported by an Aberystwyth University Doctoral Career Development Scholarship (DCDS). AH gratefully acknowledges support from the Centre for Arctic Gas Hydrate, Environment and Climate, funded by the Research Council of Norway through its Centres of Excellence (No. 223259). AR was funded by NASA grant NNX14AH93G.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Cameron, Dr Karen
• Authors: Ryan, J. C., Hubbard, A., Box, J. E., Brough, S., Cameron, K. A., Cook, J. M., Cooper, M., Doyle, S. H., Edwards, A., Holt, T., Irvine-Fynn, T., Jones, C., Pitcher, L. H., Rennermalm, A. K., Smith, L. C., Stibal, M., and Snooke, N.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
• Journal Name: Frontiers in Earth Science
• Publisher: Frontiers Media
• ISSN: 2296-6463
• ISSN (Online): 2296-6463
• Copyright Holders: Copyright © 2017 The Authors
• First Published: First published in Frontiers in Earth Science 5:40
• Publisher Policy: Reproduced under a Creative Commons License