Diagnosing Time Scales of Atmospheric Moisture Transport

Matthew Newman CIRES Climate Diagnostics Center, University of Colorado, and Physical Sciences Division/NOAA Earth System Research Laboratory, Boulder, Colorado George N. Kiladis and F. Martin Ralph Physical Sciences Division/NOAA Earth System Research Laboratory, Boulder, Colorado The climatological atmospheric moisture budget and the budget of “climate” (low-frequency) moisture anomalies and variance are determined from the 1968-2006 NCEP Reanalysis and ERA-40 datasets, for all four seasons. It is found that while the mean moisture budget is primarily a balance between moisture transport by the mean flow and mean moisture source/sinks, synoptic variability drives about half of the extratropical meridional mean moisture transport, with this transport particularly focused within “atmospheric rivers.” Additionally, the contribution to the total budget by transport by climate anomalies is generally weak except along the west coast of North America in winter. The relative importance of variations in wind and humidity to moisture transport by both the climatological basic state and synoptic and climate anomalies is also shown.