The impact of El Nino on Earth rotation from LAGEOS and LARES SLR observations

The El Nino Southern Oscillation (ENSO) is the most widely known global climatic phenomenon. It is characterized primarily by an increase of temperature above average of about two degrees of a portion of the Pacific Ocean, although the entire cycle of the phenomenon affects the entire planet. It is a climate effect with certain periodicity although not regular. In recent years the most significant ENSO events happened in 1997/98 and recently, in 2015/16. Due to thermal expansion, the sea level near the equatorial Pacific region changes and as a result, so does the inertial properties of Earth. Signs of this change can be observed on Earth’s center of mass and Earth orientation parameters (EOP). These observations are obtained from the combination results of the four space geodetic techniques contributing to the estimation of EOP and in particular, the continuous monitoring of Earth’s center of mass with satellite laser ranging (SLR) data. The latest measurement on the variation of the Earth length of day are reported. The analysis has been performed using the data of the most recent geodetic satellite LARES.