Statistical Downscaling of Seasonal Forecast of Sea Level Anomalies for
US Coasts
Abstract
Increasing coastal inundation risk in a warming climate will require
accurate and reliable seasonal forecasts of sea level anomalies at fine
spatial scale. In this study, we explore statistical downscaling of
monthly hindcasts from six current seasonal prediction systems to
provide high resolution prediction of sea level anomalies along the
North American coast, including at several tide gauge stations. This
involves applying a seasonally-invariant downscaling operator,
constructing by linearly regressing high-resolution (1/12º) ocean
reanalysis data against its coarse-grained (1º) counterpart, to each
hindcast ensemble member for the period 1982-2011. The resulting high
resolution coastal hindcasts are significantly more skillful than the
original hindcasts interpolated onto the high resolution grid. Most of
this improvement occurs during summer and fall, without impacting the
seasonality of skill noted in previous studies. Analysis of the
downscaling operator reveals that it boosts skill by amplifying the most
predictable pattern while damping the less predictable pattern.