Are there two types of la Nina?

Abstract

In this study, the existence of two types of La Nina events is examined using observations and model output. We find that cold events in the central and eastern Pacific SST, are highly correlated unlike the corresponding warm events. When two types of La Nina are defined based on the same criteria for the types of warm events, the SST and precipitation patterns between the two types of La Nina are much less distinctive or less independent. In other words, there is a strong asymmetric character between warm and cold events. This asymmetric character is also examined in 20 climate models that participate in the CMIP3. Most climate models have difficulty in simulating independently the two types of El Nino and La Nina events; however, they simulate the two types of El Nino more independently than they simulate the two types of La Nina, supporting our observational arguments to some degree. Copyright 2011 by the American Geophysical Union.