The impact of mean state errors on equatorial Atlantic interannual variability in a climate model. Issue 2 (23rd February 2015)

• Record Type: Journal Article
• Authors: Ding, Hui; Keenlyside, Noel; Latif, Mojib; Park, Wonsun; Wahl, Sebastian
• Is Part Of: Journal of geophysical research. Volume 120:Issue 2(2015:Feb.)
• Page Start: 1133
• Page End: 1151
• Publication Date: 2015-02-23
• Subjects: mean state errors -- Atlantic Nino -- tropical Atlantic variability; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2014JC010384
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Observations show that the Equatorial Atlantic Zonal Mode (ZM) obeys similar physics to the El Niño Southern Oscillation (ENSO): positive Bjerknes and delayed negative feedbacks. This implies the ZM may be predictable on seasonal timescales, but models demonstrate little prediction skill in this region. In this study using different configurations of the Kiel Climate Model (KCM) exhibiting different levels of systematic error, we show that a reasonable simulation of the ZM depends on realistic representation of the mean state, i.e., surface easterlies along the equator, upward sloping thermocline to the east, with an equatorial SST cold tongue in the east. We further attribute the differences in interannual variability among the simulations to the individual components of the positive Bjerknes and delayed negative feedbacks. Differences in the seasonality of the variability are similarly related to the impact of seasonal biases on the Bjerknes feedback. Our results suggest that model physics must be enhanced to enable skillful seasonal predictions in the Tropical Atlantic Sector, although some improvement with regard to the simulation of Equatorial Atlantic interannual variability may be achieved by momentum flux correction. This pertains especially to the seasonal phase locking of interannual SST variability. Key Points: A reasonable simulation of Atlantic Nino depends on realistic mean state Model physics must be enhanced to enable skillful predictions of Atlantic Nino