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Western Tropical Indian Ocean (WTIO) SST index

The WTIO SST anomaly index is an indicator of the surface temperatures in a cross-equatorial region spanning the western tropical Indian Ocean. It is one half of the Dipole Mode Index, an indicator of the east-west gradient in sea surface temperatures in the Indian Ocean. It is calculated with SSTs in the box 50°E - 70°E, 10°S - 10°N.

Data source

The index is calculated using the Reynolds OIv2 SST analysis, made available through the IRI Data Library, and is updated weekly (last update 14 Nov 2009).   get series (netcdf 24kB) »  get error (netcdf 24kB) »

Calculation

The anomaly is calculated relative to a climatological seasonal cycle based on the years 1982-2005. The weekly series was linearly interpolated to a daily series to calculate the climatological seasonal cycle with daily resolution. The leap day (29 February) was treated as a special case and linearly interpolated between the climatology of 28 February and 1 March. Spatial averaging of the gridded analysis was weighted by surface area. The standard deviation of the index over the period 1982-2005 is indicated on the plot.

Uncertainty

The uncertainty in the estimate of the index is shown in gray, surrounding the zero x-axis, and is based on the uncertainty estimate of the analysis. For the surface indices, it is generally small compared to the value of the index.    more details »