Moisture transport associated with large precipitation events in the Upper Colorado River Basin

Abstract

Interannual streamflow variability poses numerous water supply forecasting and management challenges for mountain snowpack‐sourced basins across the western United States. Previous studies have shown that substantial proportions of annual precipitation occur during relatively few large precipitation events (LPEs) and consequently, such events tend to be significant predictors of streamflow for many basins, including the Upper Colorado River Basin (UCRB). While some primary pathways of atmospheric moisture transport, particularly atmospheric rivers, have been linked with extreme precipitation events across the western United States, this study seeks to expand on this knowledge by quantifying the relationships between moisture transport regimes, LPEs, and streamflow observed in the UCRB. A climatological analysis of integrated vapour transport, via a self‐organizing maps synoptic classification procedure, is used to identify geographic regimes of moisture transport that lead to LPEs, as observed at snow telemetry sites across the UCRB headwaters. Trajectory analyses are also calculated to further characterize LPE‐inducing atmospheric river pathways by subbasin in the UCRB. Results indicate that LPEs throughout the basin most commonly coincide with amplified trough patterns, which advect Pacific moisture into the UCRB from the southwest, through Southern California and the Four Corners region; patterns that are positively correlated to streamflow. LPEs occurring in northern portions of the UCRB exhibit a secondary corridor, featuring west to east‐oriented moisture transport, in association with zonal to meridional flow regimes. Highly amplified ridges over the region rarely lead to LPEs, as such patterns deflect or suppress moisture from the UCRB. These results suggest that climate projections of future enhanced meridional flow aloft will lead to continued streamflow variability in the UCRB.

Holocene extreme paleofloods and their climatological context, Upper Colorado River Basin, USA

“…Dettinger et al, 2011;Ralph et al, 2006). Two main trajectories have been identified for the large precipitation event incursions into the UCRB: one involves flow from the southwest, drawing the Pacific moisture into the southern section of the UCRB; the other follows flow from the west, advecting Pacific moisture into the northern section of the UCRB (Alexander et al, 2015;Kirk and Schmidlin, 2018).…”

Investigation of Springtime Cloud Influence on Regional Climate and Its Implication in Runoff Decline in Upper Colorado River Basin

“…(2017) found that strong ridge patterns along with similar dry patterns have been increasingly common in the spring and early summer, contributing to the early 21st century drought across western North America including the UCRB. Several hypotheses have been proposed to elaborate the dynamical mechanisms of the enhanced likelihood of ridge frequency and persistency over the western United States (Burgdorf et al., 2019; Kirk & Schmidlin, 2018; Namias, 1983). One of them argues that the Arctic amplification because of rapid Arctic warming contributes to slower zonal propagation of weather patterns, which is attributable to weakened zonal winds, allowing ridges lingering over certain regions for longer time (Francis & Vavrus, 2015; Kirk & Schmidlin, 2018).…”

“…Several hypotheses have been proposed to elaborate the dynamical mechanisms of the enhanced likelihood of ridge frequency and persistency over the western United States (Burgdorf et al., 2019; Kirk & Schmidlin, 2018; Namias, 1983). One of them argues that the Arctic amplification because of rapid Arctic warming contributes to slower zonal propagation of weather patterns, which is attributable to weakened zonal winds, allowing ridges lingering over certain regions for longer time (Francis & Vavrus, 2015; Kirk & Schmidlin, 2018). In addition, the reduced zonal winds in the midlatitude may result in less contributions from orographic lift to precipitation production in the western United States.…”

ML-Based Streamflow Prediction in the Upper Colorado River Basin Using Climate Variables Time Series Data

“…In the UCRB, most mountain ranges are oriented north-south, creating a physical barrier and enhancing orographic lift (air is forced to rise and subsequently cool). As a result, the condensation increases, leading to increased precipitation rates in a given storm event on the windward mountainside [67]. The basin has consistently high monthly precipitation in the winter season (November-April), where 50$ of precipitation falls as snow [63,68].…”