A Climatology of Precipitation Efficiency for the Central Appalachian Mountains Region

Precipitation efficiency is commonly defined as the ratio of the amount of precipitation at ground level to the amount of precipitable water in the column of the atmosphere above. The value represents the fraction of available water vapor in the atmosphere that is translated into precipitation reaching the surface. Although relatively under-studied, precipitation efficiency is an important element of any hydroclimate, and variability or change in precipitation efficiency spatially or temporally has significant consequences to physical and social systems. Daily data were used to construct a seasonal climatology of precipitation efficiency for the central Appalachian Mountains region of the eastern United States for the period 1982 through 2012. The spatial variability in median precipitation efficiency across the region is presented and related to the region's physiography. Time series analyses of precipitation efficiency are presented to highlight both (1) the inter-annual variability for the purpose of identifying any large scale climate system controllers and (2) any trends that may signal a recent change in the regional climate for the purpose of engaging concerns over both future drought and increasingly extreme precipitation events.