HOSIP Research Project, Gate 3 12/17/2008

1. HOSIP Research Project, Gate 312/17/2008 Snow Model Intercomparison Project Phase 2 Victor Koren, Hydrology Group

2. Outline • Overview of the project • Project goals • Evaluation • Milestones and Deliverables • Research Future plans

3. Overview

4. Project Background • Collaborative project involving international team of snow modeling scientists from: • France, Japan, Canada, US, UK, Switzerland, Sweden, Finland, Russia, China, Germany, Portugal • Continuation of initial SnowMIP 1 project that started in 2000 and concluded in 2002

5. Project Goals • Address the need for advanced Snow modeling capabilities in a wide range of geographic areas and ecosystems. • Evaluate snow processes including: • Accumulation and melt in forested areas • Enable RFCs to gain thorough understanding of the effects of forest cover on snow accumulation and ablation • Promote collaboration between academic institutions and internationalresearchers in the field of snow science • Gain further understanding on snow science models to determine potential benefits, identify gaps in snow model techniques and make recommendations for future improvements

6. Evaluation

7. Project Contributors • Victor Koren, HSMB Scientist • Mike Smith, HSMB Hydrology Group Lead • Eric Anderson

8. Research Approach & Techniques • Use the Noah energy budget model and NWS Snow17 temperature index parameterization in the project • Made minor changes to the models to mimic canopy effects • Generate snow accumulation/ablation results for all SnowMIP2 pared (forested and open) sites using Noah and Snow17 models • Prepare simulation results and submit to the SnowMIP2 organizing committee • Present preliminary results at the IUGG conference and discuss the project progress with attending SnowMIP2 participants • Interact with the committee in analysis of results and preparation of overall summary, prepare journal paper and presentations, and consult with NCEP scientists on findings and recommendations.

9. Deliverables & Milestones

10. Critical Success Factors • Timely distribution of all SnowMIP 2 results to participants for analysis (release of SnowMIP 1 results was delayed somewhat) • Full attendance and participation of SnowMIP 2 participants at IUGG meeting to discuss results

11. Findings & Recommendations • Assessment of individual model performances indicates there is no universal ‘best’ model or subset of ‘better’ models • When all models are considered collectively, it is harder to model SWE at forested sites than open sites • A model that performs well for one year at an open site is more likely to perform well in the subsequent year. However, at forest sites there is more variability in relative model performance between years • A good performance by a model at a forest site is unlikely to guarantee a good model performance by the same model at an open site (and vice versa) • Conversely, and contrary to experience in some previous land surface model intercomparisons, the multi-model mean does not perform consistently better than the individual models

12. Findings & Recommendations, cont. • Parameterization tools and physic improvements for Snow17 (e.g., use of simulated snow depth, wind effect, a priori parameters, MODs combined with NOHRSC, etc.) will be important in river runoff prediction for an extended time period • It is critical to perform more rigorous tests, including data sensitivity, of energy models, particularly the NOHRSC model • Forest effect is significant for snowmelt timing at very dense forest canopy. There is a need to develop simple parameterizations of forest canopy effects on snow ablation/accumulation

13. Future Plans • Improve and evaluate Snow-17 a priori parameters: • Via existing HOSIP project "Lumped and Distributed Model Parameterization" • Leverage CONUS-wide simulations from NCEP-OHD project • Prepare recommendation for a new HOSIP project on an improvement of Snow-17 physics