Deriving Snow Cover Metrics for Alaska from MODIS

Abstract

Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow cover products provide an opportunity for determining snow onset and melt dates across broad geographic regions; however, cloud cover and polar darkness are limiting factors at higher latitudes. This study presents snow onset and melt dates for Alaska, portions of western Canada and the Russian Far East derived from Terra MODIS snow cover daily 500 m grid data (MOD10A1) and evaluates our method for filling data gaps caused by clouds or polar darkness. Pixels classified as cloud or no data were reclassified by: spatial filtering using neighboring pixel values; temporal filtering using pixel values for days before/after cloud cover; and snow-cycle filtering based on a time series assessment of a pixel's position within snow accumulation, cover or melt periods. During the 2012 snow year, these gap-filling methods reduced cloud pixels from 27.7% to 3.1%. A total of 12 metrics (e.g., date of first and last snow, date of persistent snow cover and periods of intermittence) for each pixel were calculated by snow year. A comparison of MODIS-derived snow onset and melt dates with in situ observations from 244 weather stations generally showed an early bias in MODIS-derived dates and an effect of increasing cloudiness exacerbating bias. Our results show that mean regional duration of seasonal snow cover is 179-311 days/year and that snow cover is often intermittent, with 41% of the area experiencing ≥2 snow-covered OPEN ACCESSRemote Sens. 2015, 7 12962 periods during a snow season. Other regional-scale patterns in the timing of snow onset and melt are evident in the yearly 500 m gridded products publically available at http://static.gina.alaska.edu/NPS_products/MODIS_snow/.

Delayed spring onset drives declines in abundance and recruitment in a mountain ungulate

“…Additional processing of the daily NSIDC snow product, to interpolate across cloudy periods and detect the start and end of snow cover periods of different lengths, was performed by the Geographic Information Network of Alaska (GINA) at the University of Alaska, Fairbanks (see http://www.gina. alaska.edu/projects/modis-derived-snowmetrics; Lindsay et al 2015). We used band 5 of the GINA snow metrics which represents the end of the continuous snow season (CSS).…”

Warming drives a front of white spruce establishment near western treeline, Alaska

“…Mean monthly maximum and minimum temperatures and mean annual precipitation for each plot location were extracted from the 800 m resolution Parameter-elevation Regressions on Independent Slopes Model (PRISM) data set for Alaska (available online at http://irma.nps.gov). Mean snow season length (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) was derived from the 500 m resolution Moderate Resolution Imaging Spectroradiometer (MODIS) Terra Snow Cover Daily L3 Global 500 m data set (Lindsay, Zhu, Miller, Kirchner, & Wilson, 2015; data available online at http://www.gina. Mean monthly maximum and minimum temperatures are aggregated from daily maximum and minimum temperatures across the period of record (Daly et al, 2008).…”

Developing Daily Cloud‐Free Snow Composite Products From MODIS and IMS for the Tienshan Mountains

“…Our ongoing work will therefore focus on reducing the IO error but not the IU error by combining the MODIS snow products with meteorological data such as temperature and precipitation. Lindsay et al (2015) used a snow-cycle filtering method to reclassify cloud pixels, which based on a time series assessment of a pixel's position within snow accumulation, cover or melt periods. Moreover, two recent had been published paper by Huang et al (2018) and Lindsay et al (2015) also give a possible solution for this problem.…”