Abstract
Abstract. This study presents a spatio-temporal continuous data set for snow cover in Iceland based on the Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000 to 2018. Cloud cover and polar darkness are the main limiting factors for data availability of remotely sensed optical data at higher latitudes. In Iceland the average cloud cover is 75 % with some spatial variations, and polar darkness reduces data availability from the MODIS sensor from late November until mid January. In this study MODIS snow cover data were validated over Iceland with comparison to manned in situ observations and Landsat 7/8 and Sentinel 2 data. Overall a good agreement was found between in situ observed snow cover, with an average agreement of 0.925. Agreement of Landsat 7/8 and Sentinel 2 was found to be acceptable, with R2 values 0.96, 0.92 and 0.95, respectively, and in agreement with other studies. By applying daily data merging from Terra and Aqua and a temporal aggregation of 7 d, unclassified pixels were reduced from 75 % to 14 %. The remaining unclassified pixels after daily merging and temporal aggregation were removed with classification learners trained with classified data, pixel location, aspect and elevation. Various snow cover characteristic metrics were derived for each pixel such as snow cover duration, first and last snow-free dates, deviation and dynamics of snow cover and trends during the study period. On average the first snow-free date in Iceland is 27 June, with a standard deviation of 19.9 d. For the study period a trend of increasing snow cover duration was observed for all months except October and November. However, statistical testing of the trends indicated that there was only a significant trend in June.
Highlights
On a global scale snow cover has a strong interaction with the cryosphere and ocean systems and the climate system of the Earth
Snow albedo dominates the control of its irradiance feedback, which depends on various factors such as snow depth, snow cover extent, vegetation and cloud cover (Fernandes et al, 2009; Qu and Hall, 2007)
Manned observations of snow cover from the Icelandic Meteorological Office (IMO) are reported daily at 09:00. Observations are made both at the local site where the instruments are located as well as in mountains where applicable; these are reported as local snow cover (SNC) and snow cover in mountains (SNCM)
Summary
In the Northern Hemisphere the spring snow cover extent has decreased significantly, influencing the dynamics of spring melt intensity and timing in recent years (Adam et al, 2008; Barnett et al, 2005; Choi et al, 2010; Hori et al, 2017). Various studies using remotely sensed data, observations and climate models unanimously agree that on the Northern Hemisphere scale snow cover extent is receding by 2.5 to 10 days per decade depending on the study period (Eythorsson et al, 2019; Fontrodona Bach et al, 2018; Choi et al, 2010; Hori et al, 2017; Wang et al, 2018; Liston and Hiemstra, 2011). Future projections with warming trends predict less precipitation to fall as snow and snowmelt to occur earlier in spring, affecting runoff and water resources downstream (Vaughan et al, 2013; IPCC, 2013)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
