Data from: Recent decreases in snow water storage in western North America

We present long-term average and annual Snow Storage Index values over
mountainous western North America, intended to represent the snow water
storage capacity (and associated change) across the region. The Snow
Storage Index represents the temporal phase difference between daily
precipitation and surface water inputs – the sum of rainfall and snowmelt
into the terrestrial systems – weighted by relative magnitudes. Different
from snow water equivalent or snow fraction, the Snow Storage Index
represents the degree to which the snowpack delays the timing and
magnitude of surface water inputs relative to preciptiation, a fundamental
component of how snow water storage influences the hydrologic cycle.
 Our analysis of a 64-year modeled dataset and 34-year
observation dataset shows that the Snow Storage Index has decreased
significantly across mountainous, western North America, due primarily to
substantially earlier snowmelt and rainfall in spring months, with
additional declines in winter precipitation. The Snow Storage Index and
associated trends offer a new perspective on hydrologic sensitivity to
climate change which have broad implications for water resources and
ecosystems.