Interdecadal change in the relationship between the tropical easterly jet and tropical sea surface temperature anomalies in boreal summer
The interdecadal change in the relationship between the tropical easterly jet (TEJ) and the tropical sea surface temperature anomalies (SSTAs) in boreal summer is studied. It is found that TEJ’s relationship with the SSTAs reverses over the tropical eastern Atlantic (EA), while enhances obviously over the tropical eastern Pacific (EP) after 1981. During 1960–1980, an Atlantic Niño-like SSTA over the EA can weaken the TEJ through the upper westerly anomaly of the anomalous Walker circulation between EA and tropical Indian Ocean. In the meantime, a Pacific El Niño-like SSTA over the EP can also diminish the TEJ intensity via a Kelvin wave response east to the diabatic heating induced by enhanced precipitation in situ. Observations and model experiments show that the EA and EP SSTAs can contribute to the TEJ variability in a joint or independent manner. During 1981–2001, as the associated Pacific El Niño-like SSTA is enlarged in the magnitude and the spatial extension, it exerts a stronger impact on the TEJ variability. Different from the pre-1980 period, the SSTA over the EA featured by an Atlantic Niña-like instead of Niño-like pattern could weaken the TEJ, which doesn’t work without the co-existence of the EP SSTA. Such Atlantic Niña-like SSTA develops in the previous spring and strengthens the warm SSTA over the EP in summer, and then affects the TEJ indirectly. The interdecadal change of the TEJ-SST relationship is likely related to the changes of the variability and spatial configuration of the tropical SSTAs.
KeywordsTropical easterly jet Tropical SST anomalies Interdecadal change Walker circulation Kelvin wave response
The authors thank the constructive comments and suggestions from two anonymous reviewers, which help greatly to improve the article. This research is jointly supported by the National Key Research and Development Projects of China (Grant No. 2016YFA0600601), the National Natural Science Foundation of China (Grant Nos. 41530530, 41875087, 41775043 and 41805057) and the Guangdong Natural Science Foundation (Grant No. 2018A030310023). RC acknowledges the support of the Fundamental Research Funds for the Central Universities. SH also acknowledges the support of the high-performance grid computing platform of Sun Yat-sen University.
- Chen H, Ding Y, He J (2007) The structure and variation of tropical easterly jet and its relationship with the monsoon rainfall in Asia and Africa. Chin J Atmos Sci 31:926–936Google Scholar
- Kalnay E, Kanamitsu M, Kistler R et al (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471. https://doi.org/10.1175/1520-0477(1996)077%3c0437:TNYRP%3e2.0.CO;2 CrossRefGoogle Scholar
- Koteswaram P (1958) The easterly jet stream in the tropics. Tellus 10:43–57. https://doi.org/10.1111/j.2153-3490.1958.tb01984.x CrossRefGoogle Scholar
- Krishnamurti TN, Bhalme HN (1976) Oscillations of a monsoon system. Part I. Observational aspects. J Atmos Sci 33:1937–1954. https://doi.org/10.1175/1520-0469(1976)033%3c1937:OOAMSP%3e2.0.CO;2 CrossRefGoogle Scholar
- Zhu Y, Yang X (2003) Relationships between Pacific decadal oscillation (PDO) and climate variability in China. Acta Meteorol Sin 61:641–654Google Scholar