31 January 2020
El-Nino is the warming phase of the climate oscillation stretching over South Pacific. It comes back on South American Coasts with characteristic periods of 2.2, 3.6, 5.8 years. It is accompagnied by a reinforcement of the East-West circulation in the upper troposphere, leading to atmospheric angular momentum increase. Angular momentum balance implies that the Earth rotation decelerates or that the length-of-day increases. During the winter 2015-2016 (summer in southern hemisphere) El-Nino is so strong that it impresses directly the seasonal variation of the length-of-day, causing an anomaly of about 0.5 ms.
This is evidenced by the following plot: observed length-of-day variations (with respect to 86400 s TAI) - the red curve - is compared with the atmospheric angular momentum changes reconstructd from meteorological data - the blue curve.
Link
http://hpiers.obspm.fr/eop-pc/analy... is a daily update of this comparison
Christian Bizouard, IERS Earth Orientation Center