The Arctic System
Reanalysis: Motivation, Development, and Performance
David H. Bromwich
Ohio State University
28 Feb, 12:30, in NCWCP Auditorium
Abstract:
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.