Abstract
Alaska and the Yukon are a challenging area to develop observationally
based spatial estimates of meteorology. Complex topography, frozen
precipitation undercatch, and extremely sparse observations all limit
our capability to accurately estimate historical conditions. In this
environment it is useful to develop probabilistic estimates of
precipitation and temperature that explicitly incorporate
spatiotemporally varying uncertainty and bias corrections. In this paper
we exploit recently-developed ensemble Climatologically Aided
Interpolation (eCAI) systems to produce daily historical observations of
precipitation and temperature across Alaska and the Yukon territory at a
2 km grid spacing for the time period 1980-2013. We extend the previous
eCAI method to include an ensemble correction methodology to address
precipitation gauge undercatch and wetting loss, which is of high
importance for this region. Leave-one-out cross-validation shows our
ensemble has little bias in daily precipitation and mean temperature at
the station locations, with an overestimate in the daily standard
deviation of precipitation. The ensemble has skillful reliability
compared to climatology and significant discrimination of events across
different precipitation thresholds. Comparing the ensemble mean
climatology of precipitation and temperature to PRISM and Daymet v3 show
large inter-product differences, particularly in precipitation across
the complex terrain of SE and northern Alaska. Finally, long-term mean
loss adjusted precipitation is up to 36% greater than the unadjusted
estimate in windy areas that receive a large fraction of frozen
precipitation.