Synoptically forced hydroclimatology of major Arctic watersheds in general circulation models; Part 2: Eurasian watersheds

Abstract

A synoptic climatology of daily sea level pressure patterns over Eurasia has been created and used to assess simulations of regional circulation and hydroclimatology from fourteen general circulation models (GCMs). The quality of simulated circulation varies considerably among both individual models and seasons, with summer and winter showing the best agreement with reanalysis data. Close examination of five select models reveals a tendency for GCMs to either over- or under-emphasize the strength and persistence of the winter storm track over Eurasia, with an overemphasized track resulting in better agreement with reanalyses on annual time-scales. Although pronounced, these biases have relatively little impact on the hydroclimatology of the Ob, Yenisey, and Lena watersheds. Instead, large-scale precipitation biases appear to be primarily the result of systematic errors in simulated precipitation processes, perhaps related to relevant parameterization schemes. Finally, an effort was made to identify and characterize 20th century precipitation trends related to greenhouse gas induced climate change, by decomposing precipitation time series on the basis of variability in circulation and the mean intensity of precipitation events. Results suggest the influence of anthropogenic climate change over the past forty years is masked by natural variability. Copyright © 2008 Royal Meteorological Society