Sub-Seasonal Snowpack Trends in the Rocky Mountain National Park Area, Colorado, USA

Abstract

We present a detailed study of the snowpack trends in the Rocky Mountain National Park (RMNP) using snow telemetry and snow course data at a monthly resolution. We examine the past 35 years (1981 to 2016) to explore monthly patterns over 36 locations and used some additional data to help interpret the changes. The analysis is at a finer spatial and temporal scale than previous studies that focused more on aggregate-or regional-scale changes. The trends in the first of the month's snow water equivalent (SWE) varied more than the change in the monthly SWE, monthly precipitation or mean temperature. There was greater variability in SWE trends on the west side of the study area, and on average the declines in the west were greater. At higher elevations, there was more of a decline in the SWE. Changes in the climate were much less in winter than in summer. Per decade, the average decline in the winter precipitation was 4 mm and temperatures warmed by 0.29 • C, while the summer precipitation declined by 9 mm and temperatures rose by 0.66 • C. In general, November and March became warmer and drier, yielding a decline of the SWE on December 1 st and April 1 st , while December through February and May became wetter. February and May became cooler.

Changes in Regional Snowfall in Central North America (1961–2017): Mountain Versus Plains

“…The slight decreasing trends of 0-2 mm/year observed in the Front Range (Figure 5a) roughly agreed with Knowles et al [14]. For 1981-2010, the increasing trends remained in the two mountain ranges, but extending to southwestern Wyoming and southern Idaho (Figure 5b), which again disagrees with the decreasing trends observed by Clow [32] and Fassnacht et al [33]. Both Clow [32] and Fassnacht et al [33] used precipitation from the SNOTEL dataset as their study variables.…”

“…For 1981-2010, the increasing trends remained in the two mountain ranges, but extending to southwestern Wyoming and southern Idaho (Figure 5b), which again disagrees with the decreasing trends observed by Clow [32] and Fassnacht et al [33]. Both Clow [32] and Fassnacht et al [33] used precipitation from the SNOTEL dataset as their study variables. Unfortunately, the SNOTEL snow depth data, which we used to derive snowfall, are only available after 2000, and thus were unsuitable for this study.…”

“…The first period is 1949-2004 used by Knowles et al [14], which is of a similar length to our study period, but with a different starting point; the second period is 1981-2010, which is a shorter period and corresponds to the one used in Clow [32] and Fassnacht et al [33]. The same data filtering criteria of snowfall were applied to both periods.…”

“…In the Front Range, Knowles et al [14] found a relative mix of trends, with seven stations showing decreasing trend and eight stations showing increasing trend from 1949 to 2004. Also in the Front Range using SNOTEL stations, which are largely located in the mountains, Clow [32] and Fassnacht et al [33] found a decrease of winter precipitation for 1978-2007 and 1981-2016, respectively. These results in the Front Range differ from the increasing trend of snowfall that we found from 1961 to 2017 (Figure 2a).…”

Optimal design of snow stake networks to estimate snow depth in an alpine mountain range

“…Snowpack distribution is also traditionally approached by using in situ data and applying interpolation procedures or hydrological models that include estimates of snow processes (e.g., accumulation and fusion; Collados‐Lara, Pardo‐Iguzquiza, & Pulido‐Velazquez, ; Zeinivand & De Smedt, ). SWE is normally measured using snow pillows based on the hydrostatic pressure created by overlying snow (e.g., SNOTEL system, Fassnacht, Dressler, & Bales, ; Fassnacht, Venable, McGrath, & Patterson, ).…”