This map shows the historical probability (given in percentile) of seasonal average monthly temperature falling within the upper (hot), middle (normal), or bottom (cold) one-third ("tercile") of the 1961 to present historical distribution in Zambia given the state of ENSO (El Niño, Neutral, La Niña) during the previous season (e.g. Jan-Mar temperature against Oct-Dec ENSO state).
Here, the ENSO state for each season is defined according to the Oceanic Niño Index (ONI). It is using Sea Surface Temperature (SST) anomalies, based on centered 30-year base periods updated every 5 years, in the geographical box (170˚W, 5˚S, 120˚W, 5˚N). A season is considered El Niño (La Niña) if it is part of at least 5 consecutive overlapping 3-month long seasons where the ONI is above 0.5˚C (below -0.5˚C). Use the controls on the page to select the season, rainfall tercile category of interest, and ENSO state. The analysis reproduces, using same SST dataset, the following definition from NOAA.
Clicking on the map will then display, for the selected point, yearly seasonal temperature averages time series. The colors of the bars depict what ENSO phase it was that year, and the horizontal lines show the historical terciles limits. This allows to quickly picture what years fell into what ENSO Phase and into what Temperature Tercile category.
NB: This is not a forecast. It is based just on historical observations of temperature and SST. However, it would be a good tool for exploring the effect of different ENSO phases on seasonal rainfall.
Reference for ENSO phases definition: V. E. Kousky and R. W. Higgins, 2007: An Alert Classification System for Monitoring and Assessing the ENSO Cycle. Wea. Forecasting, 22, 353–371. doi: http://dx.doi.org/10.1175/WAF987.1
Observations
Monthly Temperature: Reconstructed temperature (minimum and maximum) over land areas on a 0.0375˚ x 0.0375˚ lat/lon grid from Zambia Meteorological Department. Minimum and maximum temperature time series (1961 to 2020) were generated by combining quality-controlled station observations with down-scaled climate reanalysis product.
Sea Surface Temperature: Extended Reconstructed Sea Surface Temperatures (ERSST), at 2˚ spatial resolution, beginning January 1854 from NOAA NCDC.
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