Comparison of Different El Niño and La Niña Events
Details of Calculations
For each dataset, a plot of anomalies (mean- climatology) is created for ENSO events within the time-period of the dataset. The months start in July before the peak of the event and end in June after the event. Events are selected using the ONI (or Nino 3.4 for years before the ONI is defined). In general, we tried to use matching events for different variables. In addition, the composite, or overall average of the anomalies for all events is created and plotted. Finally, the standard deviation of the anomalies is calculated and plotted so users can see where events tend to differ.
Events are defined by the DJF values of the NOAA Oceanic Nino Index (ONI) for a year. Plots have that value in the title so users can compare stronger to weaker events.
DatasetsThe set of datasets we used are as follows:
- ECMWF Reanalysis v5 (ERA5): 1940-near present
- Ocean Reanalysis System 5 (ORAS5): 1958-near present
- NCEP Global Ocean Data Assimilation System (GODAS): 1981-near present
- NClimGrid Observed Dataset: 1895-near present
- NOAA Extended Reconstructed SST V5: 1854-near present
- Permanent Service for Mean Sea Level (PSMSL) Tidal Gauge Data: varies. As early as 1807-2022
One of the main issues with the anomaly plots is there is a strong trend in some variables such as 2m Temperature. This makes anomalies look warmer the later the event and can mask ENSO response to the climate at the time of the event.
Future AdditionsAs we have the resources, we plan to add the following.
- Water year to date anomalies for some variables (e.g. Oct-end month)
- Seasons in addition to months (3-month seasons).
- Composites of events before 1940, either using the 20CRV3 or some of the longer datasets such as NOAA ERSST.
- More dataset types such as biological datasets.