The Arctic System Reanalysis: Motivation, Development, and Performance

David H. Bromwich
Ohio State University
  28 Feb, 12:30, in NCWCP Auditorium

The Arctic System Reanalysis (ASR) is a multi-agency, university-led retrospective analysis (reanalysis) of the greater Arctic, approximately defined as extending poleward from the headwaters of the major northward flowing rivers. ASR blends atmospheric observations, satellite data, and output from the polar-optimized version of the Weather Research and Forecasting (WRF) model using the WRF 3-D variational data assimilation system in cycling mode. With the Arctic’s vital link to global climate change, this physically-consistent, comprehensive integration of the regional climate and synoptic meteorology of the Arctic for 2000-2012 provides a high resolution depiction in space (15 km horizontal resolution with 71-vertical levels) and time (3h) of the atmosphere-sea ice-land surface system. A comparison with approximately 4500 surface observations illustrates that ASR reproduces the near-surface atmospheric variables with high skill. A broad-scale analysis of precipitation and site-specific comparisons of incoming radiative fluxes demonstrates substantial improvement over previous versions of ASR. ASR’s high-resolution depiction of topography and detailed land surface, including weekly-updated vegetation and realistic sea-ice characteristics (fractional sea-ice, thickness, and snow cover), allows fine-scale processes between the surface and atmosphere to be well captured. In particular, case studies of mesoscale processes (e.g., polar lows, tip jets, etc.) show ASR’s improved skill in atmospheric circulation and near-surface wind events throughout the Arctic. ASR’s gridded output may be used as boundary conditions in atmospheric/coupled models, verification of regional processes throughout the Arctic, and improved siting for future observation networks. Finally, ASR permits a reconstruction of the Arctic system's rapid change since the beginning of the 21st century, thus complementing global reanalyses. Currently completed through 2012, continued production will bring this data set up to date by mid-2017.