Why were some La Niñas followed by another La Niña? |
| |
| Authors: | Zeng-Zhen Hu Arun Kumar Yan Xue Bhaskar Jha |
| |
| Institution: | 1. NCEP/NWS/NOAA, Climate Prediction Center, 5830 University Research Court, College Park, MD, 20740, USA
2. WYLE Science, Technology and Engineering Group, Houston, TX, USA
|
| |
| Abstract: | This paper investigates why some La Niña events are followed by another La Niña and some others are not. We propose two preconditions that result in continuation of a La Niña. The first one is that La Niña must be a strong event (a major La Niña). This ensures that the reflected Rossby wave signal at the eastern boundary of the Pacific has a strong westward propagating cold ocean temperature anomaly over the off-equatorial region. The off-equator cold anomaly may not be conducive to the equatorial recharge process, and as a result, may favor the persistence of cold ocean subsurface temperature anomaly and prevent the transition from La Niña to El Niño. The second precondition is whether there are eastward propagating downwelling Kelvin waves during the decay phase of a major La Niña. Eastward propagating downwelling Kelvin waves could lead to demise for a tendency for a follow-up La Niña. The equatorial Kelvin wave activities are associated with fluctuations of surface wind in the equatorial far-western Pacific. The analysis suggests that both the surface wind in the equatorial far-western Pacific and the recharge/discharge of the equatorial Pacific are indicators for occurrence or no occurrence of a follow-up La Niña event. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
