Climate DynamicsPrecipitation Extremes and their relation to climatic indices in the Pacific NorthwestUSA

There has been focus on the influence of climate indices on precipitation extremes inthe literature. Current study presents the evaluation of the precipitation-basedextremes in Columbia River Basin (CRB) in the Pacific Northwest USA. We firstanalyzed the precipitation-based extremes using statistically (10 GCMs) anddynamically downscaled (3 GCMs) past and future climate projections. Sevenprecipitation-based indices that help inform about the flood duration/intensity are used.These indices help in attaining first-hand information on spatial and temporal scales fordifferent service sectors including energy, agriculture, forestry etc. Evaluation of theseindices is first performed in historical period (1971-2000) followed by analysis of theirrelation to large scale tele-connections. Further we mapped these indices over thearea to evaluate the spatial variation of past and future extremes in downscaled andobservational data. The analysis shows that high values of extreme indices areclustered in either western or northern parts of the basin for historical period whereasthe northern part is experiencing higher degree of change in the indices for futurescenario. The focus is also on evaluating the relation of these extreme indices toclimate tele-connections in historical period to understand their relationship withextremes over CRB. Various climate indices are evaluated for their relationship usingPrincipal Component Analysis (PCA) and Singular Value Decomposition (SVD).Results indicated that, out of thirteen climate tele-connections used in the study, CRBis being most affected inversely by East Pacific (EP), Western Pacific (WP), EastAtlantic (EA) and North Atlaentic Oscillation (NAO).