The Influence of Interacting Modes of Climate Variability on North American Precipitation and Temperature

Seasonal precipitation and temperature anomalies in North America are influenced by multiple climate patterns depending on region and season. Here we present an observational analysis of four of the leading modes of climate variability that influence North American climate: El Niño – Southern Oscillation (ENSO), the Atlantic Multidecadal Oscillation (AMO), Pacific – North American (PNA) Pattern, and the Northern Annular Mode (NAM). Many studies have analyzed the role of climate patterns on precipitation and temperature variability over North America, however, there is still ambiguity as to how these large-scale patterns interact to affect the general circulation and regional climate of North America. Making sense of this variability can provide information for decision makers responsible for planning in our agricultural, natural resource, industrial, and urban environments. In this study, we use the Climate Research Unit (CRU) TS v4.00 monthly precipitation and temperature data to determine which single climate mode has the largest regional influence on precipitation and temperature for the boreal winter and summer seasons. We then identify the most common combination of modes in operation and their influence on North American temperature and precipitation. Additionally, as global climate change becomes increasingly influential, we present an analysis using the NCAR CESM1 global climate model to explore the combined influence of ENSO and the AMO on North American climate under historical conditions as well as the end-of-century RCP 8.5 global warming scenario.