Latitude - longitude gridding

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All of the fields displayed as Lat-Long maps are fields of gridded monthly means. The same gridding routine is used for all fields.

The monthly means at the array locations are gridded to 1° in latitude and 1° in longitude using the following method.

  1. Anomalies are computed at the nominal TAO / TRITON array coordinates by subtracting climatological averages from the monthly means after bilinearly interpolating the climatology field in latitude and longitude to the array coordinates.
  2. The anomalies are linearly interpolated, first in latitude, and then in longitude, to a 1 deg by 1 deg grid.
  3. The interpolated anomaly field is smoothed by passing a gappy running mean filter over the data twice. This is equivalent to convolution with a triangle filter (which is approximately equivalent to a Hanning filter). This smoothing is done first in the zonal direction, and then in the meridional direction. Triangle filter widths are 21 deg in the zonal direction, and 5 deg in the meridional direction.
  4. Finally, this gridded and smoothed anomaly field is added to the climatology to produce the gridded monthly mean field, after bilinearly interpolating the original climatology to the 1 deg by 1 deg grid.

This gridding method was developed by Dr. William S. Kessler, Dr. Michael J. McPhaden, and Dai McClurg, all at PMEL/NOAA. For more examples of Lat Lon Maps, see the TAO / TRITON Data Display page.