Observed and Simulated Spring and Summer Dryness in the United States: The Impact of the Pacific Sea Surface Temperature and Beyond

TitleObserved and Simulated Spring and Summer Dryness in the United States: The Impact of the Pacific Sea Surface Temperature and Beyond
Publication TypeJournal Article
Year of Publication2018
AuthorsZhao, Siyu, Deng Yi, and Black Robert X.
JournalJournal of Geophysical Research: Atmospheres
Volume123
Date Published01/2018
Abstract / Summary

This study characterizes major modes of variability in the spring and summer U.S. dryness, as measured by the seasonal total number of dry (no-precipitation) days, and assesses the impact of the Pacific sea surface temperature. The most severe spring and summer dry conditions typically occur in the western United States. Maximum covariance analysis reveals that the Pacific Decadal Oscillation (PDO) is the primary driver of interannual variability in the U.S. dryness. El Niño–Southern Oscillation (ENSO) also contributes in part (especially during spring). Beyond the PDO and ENSO impact, interannual variations in spring dryness exhibit a meridional dipole structure, while variations during summer are related to a northwest-southeast (NW-SE) oriented dipole. The spring meridional dipole is associated with circulation anomalies resembling the West Pacific teleconnection pattern, while the summer NW-SE dipole is a downstream manifestation of a quasi-stationary wave train. A parallel analysis of Coupled Model Intercomparison Project's fifth phase models' historical simulations demonstrates that such models generally capture the relation between U.S. dryness and the PDO, albeit with varying degrees of accuracy. The models also show reasonable skill in simulating the residual meridional dipole in spring dryness variability but have difficulty representing the NW-SE oriented dipole occurring during summer. The model shortcomings isolated here largely arise from a misrepresentation of the corresponding large-scale circulation and moisture transport anomalies. These model biases suggest that great challenges exist in our ongoing pursuit of reliable projections of the U.S. hydroclimate variability.

URLhttp://doi.wiley.com/10.1002/2017JD027279
DOI10.1002/2017JD027279
Journal: Journal of Geophysical Research: Atmospheres
Year of Publication: 2018
Volume: 123
Date Published: 01/2018

This study characterizes major modes of variability in the spring and summer U.S. dryness, as measured by the seasonal total number of dry (no-precipitation) days, and assesses the impact of the Pacific sea surface temperature. The most severe spring and summer dry conditions typically occur in the western United States. Maximum covariance analysis reveals that the Pacific Decadal Oscillation (PDO) is the primary driver of interannual variability in the U.S. dryness. El Niño–Southern Oscillation (ENSO) also contributes in part (especially during spring). Beyond the PDO and ENSO impact, interannual variations in spring dryness exhibit a meridional dipole structure, while variations during summer are related to a northwest-southeast (NW-SE) oriented dipole. The spring meridional dipole is associated with circulation anomalies resembling the West Pacific teleconnection pattern, while the summer NW-SE dipole is a downstream manifestation of a quasi-stationary wave train. A parallel analysis of Coupled Model Intercomparison Project's fifth phase models' historical simulations demonstrates that such models generally capture the relation between U.S. dryness and the PDO, albeit with varying degrees of accuracy. The models also show reasonable skill in simulating the residual meridional dipole in spring dryness variability but have difficulty representing the NW-SE oriented dipole occurring during summer. The model shortcomings isolated here largely arise from a misrepresentation of the corresponding large-scale circulation and moisture transport anomalies. These model biases suggest that great challenges exist in our ongoing pursuit of reliable projections of the U.S. hydroclimate variability.

DOI: 10.1002/2017JD027279
Citation:
Zhao, S, Y Deng, and RX Black.  2018.  "Observed and Simulated Spring and Summer Dryness in the United States: The Impact of the Pacific Sea Surface Temperature and Beyond."  Journal of Geophysical Research: Atmospheres 123.  https://doi.org/10.1002/2017JD027279.