Triangulating from the cairns…
These maps represent annual estimates of the number of days of continuous seasonal snowpack from 1993 - 2022. The maps are derived from estimates of the first and last day of bare ground derived from long-term time-series of Landsat TM, ETM, and OLI imagery starting in 1993. Annual estimates represent the number of days of continuous snow cover from the fall of the previous year to the spring of the current year. For example, the 1993 estimate is the number of days of snowpack cover from fall 1992 to spring 1993. This is often called a "water year" estimate. These maps combine monthly ground snow cover fraction maps from the USGS Landsat Collection 2 Level 3 fSCA Statistics (https://doi.org/10.5066/F7VQ31ZQ) with a time-series analysis of a spectral snow index (NDSI) using a heirarchical Bayesian model (Gao et al. 2021). The combination of these two approaches allows reconstruction of detailed annual snow persistence maps from sparse imagery time-series (Landsat data have an 8 to 16-day return interval in the absence of clouds). A comparison of these data to independent in-situ observations from SNOTEL and microclimate sensors show that these products capture about 85% of spatial variation in snow persistence for recent years (2021-2022), and greater than 90% of temporal variation across the full 1993 - 2022 time-series. This data represents annual estimates from 1993 - 2022. The 30-year mean is also available. References: Gao, X., Gray, J. M., & Reich, B. J. (2021). Long-term, medium spatial resolution annual land surface phenology with a Bayesian hierarchical model. Remote Sensing of Environment, 261, 112484. https://doi.org/10.1016/j.rse.2021.112484
Knowledge graph centered on Snowpack Duration Annual Mean for the Upper Gunnis with 3 nodes and 3 connections. Top connected: Upper East River Beaver Pond, Multi-model PlanetScope snow cover classification.
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