Lettenmaier, Dennis: University of Washington (Project Lead)
Project Funding:
2014 - 2017
NRA: 2012 NASA: Interdisciplinary Research in Earth Science
Funded by NASA
Abstract:
Along the Pacific Coast of the Western U.S. most flooding occurs as a result of multi-day extreme precipitation events during the winter and late fall. These events are now recognized to be associated with thin bands of warm, moist air referred to as atmospheric rivers (ARs) that draw on enhanced tropical water vapor content, mostly originating from the tropical Pacific. Recent studies have shown that almost all of the precipitation events that lead to extreme floods in the three Pacific Coast states are associated with ARs. Given the importance of flooding events to the economy of the coastal Western U.S. region, water management agencies are concerned about possible changes in the characteristics of AR-related flooding in a warming climate. The overarching science question our research will address is Will the risk of AR-related floods in the Western U.S. change through the 21st century in response to climate change, and if so, how? We propose to address this question by using a screening approach to identify AR events associated with historic flooding in four Pacific Coast watersheds ranging from the Santa Margarita watershed (between Los Angeles and San Diego) in the south, to the Chehalis River basin, WA in the north. We will utilize enhanced information about the vertical distribution of water vapor, ice content, and other variables produced by the CloudSat/AMSR-E members of the A-Train during the period 2006-2011 to diagnose the ability of the WRF regional climate model to reproduce past AR events and associated flooding in the four river basins. We will also conduct an extended analysis using WRF simulations over the ~30 year MERRA reanalysis period, with particular attention to AR events associated with the ~15 overbank flood events in each of the four watersheds during that period. Through use of atmospheric screening analyses and analysis of streamflow observations, we will be able to focus our atmospheric modeling on the few days surrounding floods that dominate flood damage estimates. This will allow us to produce WRF simulations of AR events at much higher spatial resolution than has previously been possible (2.5 km). We will develop an integrated end-to-end simulation system consisting of the following four elements: i) atmospheric model (WRF); ii) hydrology model (VIC); iii) river hydrodynamics model (HEC-RAS); and iv) local (HAZUS) and national economic impacts (interregional input-output) models. The end-to-end simulation system will represent atmospheric and hydrologic conditions associated with AR events, as well as resulting flood damages. We will utilize this end-to-end framework to assess the implications of a warming climate for flooding and flood damages in the four watersheds, using a compositing procedure that will perturb the historic AR archive to reflect changes in AR characteristics that are implied by IPCC AR5 global climate simulations. Our proposal addresses the first subelement of the NRA, Understanding Earth system vulnerabilities to climate extremes, and specifically severe flooding. Among the elements of the holistic, end-to-end approach outlined in the NRA, our proposal includes a) Characterizing the nature, magnitude, and distinguishing attributes of the extreme event(s) being investigated; b) Identifying trends in occurrences of these extremes in regions of high human and biogeophysical ecosystem vulnerability; c) Analyzing the ramifications of human actions to recover from and/or mitigate the impacts of extreme events; and d) Incorporating findings into decision support systems used by relevant stakeholders. We plan to interact with stakeholders in both the Pacific Northwest and the northern California coastal region via debriefings of flood managers as we near completion of the project. The proposal involves a multidisciplinary team which includes hydrologists, atmospheric modelers, remote sensing scientists, and a resource economist.
Publications:
Avelino, A. F. T., Dall'erba, S. 2018. Comparing the Economic Impact of Natural Disasters Generated by Different Input-Output Models: An Application to the 2007 Chehalis River Flood (WA). Risk Analysis. 39(1), 85-104. DOI: 10.1111/risa.13006
Cannon, F., Hecht, C. W., Cordeira, J. M., Ralph, F. M. 2018. Synoptic and Mesoscale Forcing of Southern California Extreme Precipitation. Journal of Geophysical Research: Atmospheres. 123(24). DOI: 10.1029/2018JD029045
Cannon, F., Ralph, F. M., Wilson, A. M., Lettenmaier, D. P. 2017. GPM Satellite Radar Measurements of Precipitation and Freezing Level in Atmospheric Rivers: Comparison With Ground-Based Radars and Reanalyses. Journal of Geophysical Research: Atmospheres. 122(23). DOI: 10.1002/2017JD027355
Dominguez, F., Dall'erba, S., Huang, S., Avelino, A., Mehran, A., Hu, H., Schmidt, A., Schick, L., Lettenmaier, D. 2018. Tracking an atmospheric river in a warmer climate: from water vapor to economic impacts. Earth System Dynamics. 9(1), 249-266. DOI: 10.5194/esd-9-249-2018
Eiras-Barca, J., Dominguez, F., Hu, H., Garaboa-Paz, D., Miguez-Macho, G. 2017. Evaluation of the moisture sources in two extreme landfalling atmospheric river events using an Eulerian WRF tracers tool. Earth System Dynamics. 8(4), 1247-1261. DOI: 10.5194/esd-8-1247-2017
Hu, H., Dominguez, F., Kumar, P., McDonnell, J., Gochis, D. 2018. A Numerical Water Tracer Model for Understanding Event-Scale Hydrometeorological Phenomena. Journal of Hydrometeorology. 19(6), 947-967. DOI: 10.1175/JHM-D-17-0202.1
Zhang, Z., Ralph, F. M., Zheng, M. 2019. The Relationship Between Extratropical Cyclone Strength and Atmospheric River Intensity and Position. Geophysical Research Letters. 46(3), 1814-1823. DOI: 10.1029/2018GL079071
More details may be found in the following project profile(s):
