Sea-height signal tracking the Indian Ocean climate pattern

This file contains an indicator for the Indian Ocean Dipole (IOD), based on satellite observations of sea surface height anomaly, measured by radar altimeter missions such as TOPEX/Poseidon, the Jason series, and Sentinel-6. The indicator values were calculated using NASA-SSH Simple Gridded Sea Surface Height from Standardized Reference Missions Only Version 1 https://podaac.jpl.nasa.gov/dataset/NASA_SSH_REF_SIMPLE_GRID_V1 . Indicator values were calculated using cyclostationary empirical orthogonal functions (CSEOFs; Kim et al., 2015) computed by decomposing the gridded sea surface height anomalies over the time period from 1993 to 2019. After removing the linear trend from each individual gridded location, three sets of regional CSEOFs were generated, one each for the El Nino-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) and (IOD). In each case, the dominant statistical mode represents the seasonal cycle. The second most dominant mode represents the variability explained by each respective indicator and is referred to as the “indicator mode”. The seasonal mode and indicator mode are then projected onto the along-track sea surface height anomalies to produce the indicator time series through the most current date. In this case, the IOD mode was used to produce the time series contained in this file. The file with the filename "NASA_SSH_IOD_INDICATOR.txt" is always the most up-to-date time series containing the most recent data.