Using Temporal Deep Learning Models to Estimate Historical and
End-Century Daily Snow Water Equivalent over the Rocky Mountains
Abstract
In this study we construct and compare three different deep learning
(DL) models for estimating daily snow water equivalent (SWE) from
high-resolution gridded meteorological fields over the Rocky Mountain
region. Snow Telemetry (SNOTEL) station based observations are used as
the prediction target. All DL models produce higher median
Nash-Sutcliffe Efficiency (NSE) values than an analogous process-based
product, although their mean squared errors also tend to be higher.
Sensitivity of the SWE prediction to the model’s input variables is
analyzed using an explainable artificial intelligence (XAI) method,
yielding insight into the physical relationships learned by the models.
As expected, this method reveals the dominant role precipitation and
temperature play in snowpack dynamics. In applying our models to
estimate SWE throughout the Rocky Mountains, an extrapolation problem
arises since the statistical properties of SWE (e.g., annual maximum)
and geographical properties of individual grid points (e.g., elevation)
differ from the training data. This problem is solved by switching the
prediction target for all tested DL models. Finally the spatial and
temporal responses of SWE with respect to climate change is investigated
with forcings from down-scaled Coupled Model Intercomparison Project
Phase 5 (CMIP5) simulations. The projection results show a substantial
decrease in both maximum SWE and snow season length over the lower
elevation areas. Our work shows that the DL models are promising tools
for estimating SWE, and sufficiently capture relevant physical
relationships to make them useful for spatial and temporal extrapolation
of SWE values.