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Arctic System Reanalysis

Arctic System Reanalysis. Aim: Integrate all available observations into a consistent framework, providing a vehicle for monitoring and diagnosing environmental change in the Arctic. The large variations of the past decade can then be placed into a broader perspective.

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Arctic System Reanalysis

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  1. Arctic System Reanalysis • Aim: Integrate all available observations into a consistent framework, providing a vehicle for monitoring and diagnosing environmental change in the Arctic. The large variations of the past decade can then be placed into a broader perspective. • A “system reanalysis”: atmosphere, sea ice, upper ocean, land hydrology • Early experiments based on the Polar MM5 model, with transitioning now underway to the NCEP Weather Research and Forecasting (WRF) system. • Lateral boundary forcing provided by a global reanalysis, ERA-40.

  2. Primary activities to date: • Parameterization experiments targeting Arctic processes -- surface parameterizations (sea ice, terrestrial Arctic) -- PBL (strongly stable) -- Arctic clouds, radiative interactions • Evaluation of global reanalyses (ERA-40, NCEP) over Arctic • Tests of different data assimilation strategies

  3. Precipitation over Iceland from Polar MM5 Observed annual mean precipitation (mm) derived from station data, contour interval = 200 mm Annual mean precipitation, 1991-2000 derived from polar MM5 V3.5 (cm). Contour interval = 20 cm. MM5 is driven at the boundaries by ECMWF operational analyses. Courtesy of D Bromwich, Ohio State University

  4. Arctic System Reanalysis experiment domains

  5. Some findings to date: • Accuracy of regional reanalysis depends more strongly on resolution than on choice of assimilation strategy • Data-driven increments in the Arctic are large (several ºC, mb) • TOVS data have major impact on global reanalysis (ERA-40) in Arctic

  6. January 1993, 500 hPa Height Difference for ERA40 with and without TOVS/HIRS Images courtesy Per Kallberg, European Centre for Medium-Range Weather Forecasts

  7. Near-term to long-term plans: • Diagnosis of North American regional reanalysis in Arctic • SHEBA year (1997-98) to be run as prototype with enhanced WRF • Optimum use of satellite data (e.g., TOVS) • Interface with future global reanalysis of NCEP • Integration of sea ice, terrestrial, upper ocean components • International partners, additional agency partners

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