Reply on RC2

Abstract

Land surface evapotranspiration (ET) is a major source of moisture for the global hydrologic cycle. Though the influence of the land surface is well documented, moisture tracking analysis has often relied on offline tracking approaches that require simplifying assumptions and can bias results. Additionally, the contribution of the ET components (transpiration (T), canopy evaporation (C), and ground evaporation (E)) individually to precipitation is not well understood, inhibiting our understanding of moisture teleconnections in both the current and future climate. Here we use the Community Earth System Model version 1.2 with online numerical water tracers to examine the contribution of local and remote land surface ET, including the contribution from each individual ET component, to precipitation across North America. We find the role of the land surface and the individual ET components varies considerably across the continent and across seasons. Much of northern and northeastern North America receives up to 80% of summertime precipitation from land surface ET, and over 50 % of that moisture originates from transpiration alone. Local moisture recycling constitutes an essential source of precipitation across much of the southern and western regions of North America, while remote land surface moisture supplies most of the land-based precipitation across northern and eastern North America. Though the greatest contribution of remotely sourced land ET occurs in the north and east, we find the primary sources of North American land surface moisture shifts seasonally. The results highlight regions that are especially sensitive to land cover and hydrologic changes in local and upwind areas, providing key insights for drought prediction and water resource management.