Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States
Widespread droughts can have a significant impact on western United States streamflow, but the causes of these events are not fully understood. This dissertation examines streamflow from multiple western US basins and establishes the robust, leading modes of variability in interannual streamflow thr...
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ftunivarizona:oai:repository.arizona.edu:10150/624160 2023-05-15T13:15:10+02:00 Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States Malevich, Steven Brewster Woodhouse, Connie A. Russell, Joellen Anchukaitis, Kevin Castro, Chris 2017 http://hdl.handle.net/10150/624160 en_US eng The University of Arizona. http://hdl.handle.net/10150/624160 Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. atmospheric circulation climate change drought segmentation streamflow western US text Electronic Dissertation 2017 ftunivarizona 2020-06-14T08:15:33Z Widespread droughts can have a significant impact on western United States streamflow, but the causes of these events are not fully understood. This dissertation examines streamflow from multiple western US basins and establishes the robust, leading modes of variability in interannual streamflow throughout the past century. I show that approximately 50% of this variability is associated with spatially widespread streamflow anomalies that are statistically independent from streamflow's response to the El Niño-Southern Oscillation (ENSO). The ENSO-teleconnection accounts for approximately 25% of the interannual variability in streamflow, across this network. These atmospheric circulation anomalies associated with the most spatially widespread variability are associated with the Aleutian low and the persistent coastal atmospheric ridge in the Pacific Northwest. I use a watershed segmentation algorithm to explicitly track the position and intensity of these features and compare their variability to the multi-basin streamflow variability. Results show that latitudinal shifts in the coastal atmospheric ridge are more strongly associated with streamflow's north-south dipole response to ENSO variability while more spatially widespread anomalies in streamflow most strongly relate to seasonal changes in the coastal ridge intensity. This likely reflects persistent coastal ridge blocking of cool-season precipitation into western US river basins. I utilize the 35 model runs of the Community Earth System Model Large Ensemble (CESMLE) to determine whether the model ensemble simulates the anomalously strong coastal ridges and extreme widespread wintertime precipitation anomalies found in the observation record. Though there is considerable bias in the CESMLE, the CESMLE runs simulate extremely widespread dry precipitation anomalies with a frequency of approximately one extreme event per century during the historical simulations (1920 - 2005). These extremely widespread dry events correspond significantly with anomalously intense coastal atmospheric ridges. The results from these three papers connect widespread interannual streamflow anomalies in the western US - and especially extremely widespread streamflow droughts - with semi-permanent atmospheric ridge anomalies near the coastal Pacific Northwest. This is important to western US water managers because these widespread events appear to have been a robust feature of the past century. The semi-permanent atmospheric features associated with these widespread dry streamflow anomalies are projected to change position significantly in the next century as a response to global climate change. This may change widespread streamflow anomaly characteristic in the western US, though my results do not show evidence of these changes within the instrument record of last century. Doctoral or Postdoctoral Thesis aleutian low The University of Arizona: UA Campus Repository Pacific |
institution |
Open Polar |
collection |
The University of Arizona: UA Campus Repository |
op_collection_id |
ftunivarizona |
language |
English |
topic |
atmospheric circulation climate change drought segmentation streamflow western US |
spellingShingle |
atmospheric circulation climate change drought segmentation streamflow western US Malevich, Steven Brewster Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States |
topic_facet |
atmospheric circulation climate change drought segmentation streamflow western US |
description |
Widespread droughts can have a significant impact on western United States streamflow, but the causes of these events are not fully understood. This dissertation examines streamflow from multiple western US basins and establishes the robust, leading modes of variability in interannual streamflow throughout the past century. I show that approximately 50% of this variability is associated with spatially widespread streamflow anomalies that are statistically independent from streamflow's response to the El Niño-Southern Oscillation (ENSO). The ENSO-teleconnection accounts for approximately 25% of the interannual variability in streamflow, across this network. These atmospheric circulation anomalies associated with the most spatially widespread variability are associated with the Aleutian low and the persistent coastal atmospheric ridge in the Pacific Northwest. I use a watershed segmentation algorithm to explicitly track the position and intensity of these features and compare their variability to the multi-basin streamflow variability. Results show that latitudinal shifts in the coastal atmospheric ridge are more strongly associated with streamflow's north-south dipole response to ENSO variability while more spatially widespread anomalies in streamflow most strongly relate to seasonal changes in the coastal ridge intensity. This likely reflects persistent coastal ridge blocking of cool-season precipitation into western US river basins. I utilize the 35 model runs of the Community Earth System Model Large Ensemble (CESMLE) to determine whether the model ensemble simulates the anomalously strong coastal ridges and extreme widespread wintertime precipitation anomalies found in the observation record. Though there is considerable bias in the CESMLE, the CESMLE runs simulate extremely widespread dry precipitation anomalies with a frequency of approximately one extreme event per century during the historical simulations (1920 - 2005). These extremely widespread dry events correspond significantly with anomalously intense coastal atmospheric ridges. The results from these three papers connect widespread interannual streamflow anomalies in the western US - and especially extremely widespread streamflow droughts - with semi-permanent atmospheric ridge anomalies near the coastal Pacific Northwest. This is important to western US water managers because these widespread events appear to have been a robust feature of the past century. The semi-permanent atmospheric features associated with these widespread dry streamflow anomalies are projected to change position significantly in the next century as a response to global climate change. This may change widespread streamflow anomaly characteristic in the western US, though my results do not show evidence of these changes within the instrument record of last century. |
author2 |
Woodhouse, Connie A. Russell, Joellen Anchukaitis, Kevin Castro, Chris |
format |
Doctoral or Postdoctoral Thesis |
author |
Malevich, Steven Brewster |
author_facet |
Malevich, Steven Brewster |
author_sort |
Malevich, Steven Brewster |
title |
Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States |
title_short |
Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States |
title_full |
Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States |
title_fullStr |
Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States |
title_full_unstemmed |
Cool-Season Moisture Delivery and Multi-Basin Streamflow Anomalies in the Western United States |
title_sort |
cool-season moisture delivery and multi-basin streamflow anomalies in the western united states |
publisher |
The University of Arizona. |
publishDate |
2017 |
url |
http://hdl.handle.net/10150/624160 |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
aleutian low |
genre_facet |
aleutian low |
op_relation |
http://hdl.handle.net/10150/624160 |
op_rights |
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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1766267246111358976 |