CR 74:145-160 (2017)  -  DOI: https://doi.org/10.3354/cr01493

ABSTRACT: Hydroclimatic variability has increased in recent decades across the southeastern US, with more frequent droughts and heavy precipitation events. Among these extremes, past research reveals that there is much variety in the synoptic-scale circulation that controls warm-season precipitation. However, research has yet to examine the subtle variation between these circulation patterns and their influence on hydroclimate variability. This is particularly the case in the southern Appalachian Mountains, where topographic complexity mediates the relationship between large-scale circulation and precipitation characteristics. In this study, we use a self-organizing map to classify and spatially visualize synoptic-scale circulation patterns over the southeastern US from 1979 to 2014. The patterns identified in the self-organizing map are linked with daily precipitation characteristics in the region. Our results demonstrate that underlying topographic features have a marked influence on the hydroclimate, and this influence varies according to the configuration of circulation. Greater frequencies of light precipitation are observed across broad-scale regions of high elevation, to varying degrees, no matter which circulation pattern is present. In contrast, precipitation frequencies along interior valleys and leeward slopes are lower and largely limited to a subset of circulation patterns. This study demonstrates how shifts in the large-scale circulation are likely to alter the occurrence of different types of warm-season precipitation events across mountain catchments.

KEY WORDS: Hydroclimatic variability · Self-organizing maps · Southern Appalachian Mountains