2. Arctic System Reanalysis David H. Bromwich 1,2 and Keith M. Hines 1 1- Polar Meteorology Group Byrd Polar Research Center The Ohio State University Columbus, Ohio 2- Department of Geography Atmospheric Sciences Program, The Ohio State University, Columbus, Ohio.

3. Why do we need an Arctic System Reanalysis (ASR)? 1.Rapid climate change appears to be happening in the Arctic. A more comprehensive picture of the coupled atmosphere/land surface/ ocean interactions is needed. 2. Global reanalyses encounter many problems at high latitudes. The ASR would use the best available description for Arctic processes and would enhance the existing database of Arctic observations. The ASR will be produced at improved temporal resolution and much higher spatial resolution. 3. The ASR would provide fields for which direct observation are sparse or problematic (precipitation, radiation, cloud,...) at higher resolution than from existing reanalyses. 4. The system-oriented approach would provide a community focus including at least the atmosphere, land surface and sea ice communities. 5. The ASR would provide a convenient synthesis of Arctic field programs (SHEBA, LAII/ATLAS, ARM,...)

4. Great Opportunity now for ASR 1. Utilize the data storage and knowledge gained from recent reanalyses (ERA- 40, NARR) and recently compiled Polar Pathfinder products 2. SEARCH and upcoming International Polar Year (2007) Preliminary components for ASR are needed during current window of opportunity 1. Improved cloud clearing for TOVS retrievals 2. Detailed evaluation of ERA-40 and NCEP's NARR 3. Prepare polar-optimized, high resolution mesoscale model NOAA seed funding: An Initiation of Arctic Reanalysis Activity in SEARCH by Co-Investigators: Bromwich, Serreze, Tilley and Walsh to lay the groundwork for ASR

5. Seed Funding Tasks Task 1. Evaluation of ERA-40 and NCEP's NARR for the Arctic While these are the current state-of-the-art reanalyses, they each have strengths and weaknesses. The strengths can be used to set benchmarks for ASR. Documenting the weaknesses will point to those attributes that are most in need of improvement. Task 2. Enhancement of WRF for Arctic applications A great deal of knowledge has been gained from the earlier reanalyses and with operational forecasts and research simulations with Polar MM5. This knowledge must be harnessed and used to develop Polar WRF. Then Polar WRF must be properly tested in the Arctic. Task 3. Incorporation of non-atmospheric components into ASR The prior reanalyses have been primarily atmospheric, thus the ASR is the vanguard of the coupled approach. The Arctic provides a viable opportunity for the inclusion of other system components such as the land surface and sea ice, and ultimately the ocean. The interdisciplinary SEARCH project is the ideal framework. Task 4. Preliminary data assimilation activities The sensitivities of assimilated fields to the input of different types of polar data will be evaluated and documented. It is important that the input data include previously unused data such as some high-latitude Canadian rawinsondes, some Russian NP observations, and VTPR and TOVS information. Also, GPS occultation soundings and MODIS observations need to be examined.

6. Issues for ASR Raised at High-Latitude NWP Workshop in Fairbanks, Alaska October 2003 Spatial resolution 20-30 km Southern margin at 45 N Time period?... 1957-present? Land surface data assimilation Better land surface data for Asia Treatment of sea ice including snow cover Mixed-phase clouds and supercooled water Diamond dust Very stable boundary layer Horizontal pressure gradient near steep terrain Upper boundary condition Assimilate radiances or retrievals into the WRF 3DVAR? Computational needs International participation Funding Distribution of tasks

7. Lessons from Polar MM5 A. The Pennsylvania State University (PSU)-National Center for Atmospheric Research (NCAR) Fifth-generation Mesoscale Model (MM5) has been adapted for polar applications (1) Real-time forecasting for Antarctica (AMPS) (2) Forecasting for the Arctic Rivers (RIMS) Project (3) Contemporary climate studies (4) Paleoclimate studies B. Polar Modifications to MM5 (1) Revised cloud / radiation interaction (2) Modified explicit ice phase microphysics (3) Optimized turbulence (boundary layer) parameterization (4) Implementation of a sea ice surface type (5) Improved treatment of heat transfer through snow/ice surfaces (6) Improved upper boundary treatment C. Future Modifications for Polar MM5 (1) Improved treatment of horizontal pressure gradient force (2) Additional testing and development of upper boundary treatments (3) Improved snow/ice albedo parameterization D. Future after Polar MM5?

8. RIMS Surface Temperature at Barrow (71.3 N, 156.78 W, elev = 4m) 147101316192225281471013 -35 -30 -25 -20 -15 -10 -5 0 5 o C Observation PMM5 forecast April 2003 May 2003

9. RIMS Surface Wind Speed at Barrow (71.3 N, 156.78 W, elev = 4m) 147101316192225281471013 -2 0 2 4 6 8 10 12 14 16 m/s OBS PMM5 forecast April 2003 May 2003

10. WRF will be the base atmospheric model for ASR http://wrf-model.org/ The Weather Research and Forecasting Model is in production by multiple agencies and development groups. The "next generation" model after MM5, ETA, etc. will provide an advanced mesoscale forecast and assimilation system. WRF, a community model, will provide closer ties between research and applications. Up to 1 km resolution Portable, efficient, parallel-friendly Currently in development. Version 1.3 is available to public.

11. Projected Timeline for WRF Project

12. WRF Development Teams

13. 1 10 100 km Cumulus Parameterization Resolved Convection LES PBL Parameterization Two Stream Radiation 3-D Radiation Model Physics in High Resolution NWP Physics “No Man’s Land”

14. ASR has the Potential to be a Flagship Activity under SEARCH A. A multi-disciplinary approach for monitoring the Arctic environment B. Provides a 50-yr context for current climate change C. Can monitor future climate change D. Major resources will be required to prepare for the ASR and to execute it. E. Now is the ideal time to undertake the ASR.