On the Fragile Relationship Between El Niño and California Rainfall. Issue 2 (17th January 2018)

• Record Type: Journal Article
• Authors: Lee, Sang‐Ki; Lopez, Hosmay; Chung, Eui‐Seok; DiNezio, Pedro; Yeh, Sang‐Wook; Wittenberg, Andrew T.
• Is Part Of: Geophysical research letters. Volume 45:Issue 2(2018)
• Page Start: 907
• Page End: 915
• Publication Date: 2018-01-17
• Subjects: El Niño -- California rainfall -- ENSO flavor -- teleconnection -- stationary Rossby wave -- 2015–2016 El Niño; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL076197
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The failed influence of the 2015–2016 El Niño on California rainfall has renewed interest in the relationship between El Niño and U.S. rainfall variability. Here we perform statistical data analyses and simple model experiments to show that sufficiently warm and persistent sea surface temperature anomalies (SSTAs) in the far eastern equatorial Pacific are required to excite an anomalous cyclone in the North Pacific that extends to the east across the U.S. West Coast and thus increases rainfall over California. Among the four most frequently recurring El Niño patterns considered in this study, only the persistent El Niño, which is often characterized by the warm SSTAs in the far eastern equatorial Pacific persisting throughout the winter and spring, is linked to such extratropical teleconnection patterns and significantly increased rainfall over the entire state of California. During the last 69 years, only three of the 25 El Niño events (i.e., 1957–1958, 1982–1983, and 1997–1998) are clearly identified as the persistent El Niño. In addition, the monthly rainfall variance explained by El Niño is less than half that caused by internal variability during the 25 El Niño. Therefore, the rarity of persistent El Niño events combined with the large influence of internal variability effectively explains the fragile relationship between El Niño and California rainfall. Key Points: This study explores why some historical El Niño events significantly increased rainfall in California but some other events did not Statistical data analyses and model experiments show that persistently warm far eastern Pacific excites an optimal stationary wave pattern During the last 69 years, only three such events have occurred, which explains the fragile relationship between El Niño and California rainfall