Description:
Top: Time series of the three-month running average of the standardized Central Equatorial Indian Ocean Index (CEI) -- monthly mean sea surface temperatures anomalies averaged over the region 0° - 15°S latitude, 50°E - 80°E longitude. The climatological base period for the anomalies is 1971-2000. Anomalies are standardized with respect to the period Dec 1981-present.
Middle: Time series of the three-month running average of the standardized North Tropical Atlantic Index (NATL) -- monthly mean sea surface temperature anomalies averaged over the region 10°N - 20°N latitude, 20°W - 80°W longitude. The climatological base period for the anomalies is 1971-2000. Anomalies are standardized with respect to the period Dec 1981-present.
Bottom: Time series of the three-month running average of the standardized NATL index (dotted line), three-month running average of the standardized NINO3 index (monthly mean SST anomalies averaged over the region 5°S - 5°N latitude, 150°W - 90°W longitude; dashed line), and the standardized difference between NATL and NINO3 (NATL minus NINO3; solid red line).
NCEP is
an acronym for the US National Centers for Environmental Prediction.