Empirical Downscaling of High-Resolution Regional Precipitation From Large-Scale Reanalysis Fields

This study describes an EOF-based technique for statistical downscaling of high spatial resolution monthly mean precipitation from large scale reanalysis circulation fields. The method is demonstrated and evaluated for four widely-separated locations: the Southeast United States, the Upper Colorado River Basin, China’s Jiangxi Province, and Central Europe. For each location, the EOF-based downscaling models successfully reproduce the observed annual cycle while eliminating the biases seen in NCEP/NCAR Reanalysis precipitation. They also frequently reproduce the monthly precipitation anomalies with greater fidelity than the precipitation field derived directly from reanalysis and outperform a suite of regional climate models over the two US locations. With the relatively high skill achieved over a range of climate regimes, this technique may be a viable alternative to numerical downscaling of monthly mean precipitation for many locations.