The ENSO index is computed with preprocessed altimeter sea level maps, which are corrected for the annual, seasonal and 60-day signals. However, the sea level maps are not corrected for the long-term trend, which directly affects the final indicator.
In January 2020, the processing of the ENSO index has been updated so that the altimeter sea level maps are now corrected for the trend in each grid point. In addition, the reference period used to estimate the periodic signals has been upgraded and changed from 1993-2013 to 1993-2016. There is no change in the processing for SST maps.

Direct access to ENSO temporal series maps can be found here. Data are updated on a monthly basis.