El Niño Southern Oscillation (ENSO) - warm (El Niño) and cold (La Niña) years are based on a +/- 0.5°C threshold of the November thru March average Niño 3.4 region (5°N-5°S, 120°-170°W) sea-surface temperature anomaly (based on the 1981-2010 base period). Neutral years are when when the average Niño 3.4 anomaly is -0.5°C > 0 < 0.5°C.
Select period based on La Niña, El Niño, Neutral - Selecting this option will filter the season/year selection box to show only the selected ENSO years. For example, if La Niña is selected, the season/years that will be avilable to plot will be La Niña years. This is useful if you want to compare snow depth for specific years based on ENSO.