1. A Northwest Consortium for Regional Climate Modelling
Cliff Mass
Department of Atmospheric Sciences
University of Washington

2. Society needs reliable information on the regional implications of climate change
Infrastructure decisions are being made now for assets that will last well into the current century when the impact of GW will be substantial
Adaptation planning
Motivation for mitigation efforts

3. Bottom Line of the Talk
There is only one viable method for producing the required regional climate predictions: dynamical downscaling of global climate models But to do this right, there is much that is required.

4. Requirements
The use of large numbers of global model simulations (GCMs) to explore initial condition, model, and physics uncertainty.
Filtering to remove GCMs unable to simulate realistically the current climate
Use of sufficient resolution in the regional climate models (minimum km grid spacing) to get realistic NW circulations
Use of an appropriate nested domain structure of the regional simulations (MUST include the Rockies with sufficient resolution)
Must have sophisticated post-processing to reduce biases and get reliable probabilities.

5. Two Sobering Facts
No one in the NW has done such downscaling right yet
Too few GCM’s applied to dynamical downscaling
Primitive post-processing
Statistical downscaling
Getting the wrong answers from inadequate efforts can be either useless or costly for society. No answer is better than the wrong answer.

6. Why haven’t we done it correctly?
Lack of computer resources and personnel
Too few GCM runs available, so uncertainty has not been explored.
Lack of filtering of unrealistic GCMs
Deficiencies of regional climate models (e.g., snow in NOAH Land Surface Model)
Lack of familiarity of some climate groups with mesoscale meteorology of the region

7. And we have not even talked about another essential component of regional climate prediction
Coupling the regional climate simulations with:
Hydrological models
Air quality models
Coastal ocean models
Fire models and others

8. The Challenge: Can We Do This Right, Together?
Combine regional resources and personnel so that together we can do what one group cannot accomplish alone.
There is a precedent for such combination of resources: the Northwest Modeling Consortium.

9. Many of the technical issues are very similar….

10. Dynamical Downscaling Not Statistical Downscaling
Only fully dynamical downscaling can hope to simulate the non-linearities and complexities of the future climate response.
Examples:
Location and distribution of precipitation changes as stability changes.
Onshore flow and coastal marine clouds enhanced by greater onshore pressure gradients
Albedo feedbacks as snow melts.

11. Echam-5 versus WRF

13. Removing Unrealistic GCMs
The quality of the available (CMIP-5) GCMs vary, with some unable to produce a realistic simulation of the contemporary climate over the western U.S.
These must be removed from consideration for downscaling work.

16. Dozens of downscaled GCM runs not 1-3
There is substantial uncertainty in the GCM simulations and a handful of simulations can not get a handle on the inherent uncertainties.
Sources: physics uncertainty, initial state uncertainty, emission uncertainty, and many more.
GCMs produce a wide variety of local solutions

18. Initial Condition Uncertainy
Dr. Clara Deser of NCAR showed that simply by varying the start times of simulations of the same GCM can produce very different regional results decades hence.

21. Sufficient resolution and proper domains

22. Over the Northwest, the simulations must have a grid spacing of a least km grid spacing Based on over 10 years of twice-daily simulations at km at the University of Washington, with objective verification

24. 150 km versus 12 km

25. 36-km

26. 12-km

27. The Proper Domain Structure is Crucial
GCMs have insufficient resolution to define key regional weather features (e.g., major terrain features), resulting in large simulation errors that make their results unreliable for local decision making.
Regional climate simulation must have enough resolution (~50km) on a large enough grid to get the Rockies right—or cold air spills over the Northwest from the cold interior

28. Cold Waves Under Global Warming
PCM
Cold
Wave
Under
Global
Warming
12 Feb 1990

29. Seattle 2050

31. PCM and ECHAM-5 Driving Small Domain MM5: Crazy Cold Waves

32. Sophisticated post-processing
Remove systematic bias based on contemporary periods.
Weight ensemble of climate simulations based on their quality.
Produce calibrated probabilistic guidance.

33. Use Bayesian Model Averaging, calibrated on a contemporary period, to produce probabilistic regional climate predictions.

34. Proven approach for weather forecasting

35. Integration of ancillary physics/applications (e
Integration of ancillary physics/applications (e.g, hydro, coastal ocean, air quality) to create a total environmental modeling system

37. The Northwest Climate Modeling Consortium: A Proposal
Combine resources of regional government entities, state and Federal agencies, foundations, academic institutions, tribes, and other to create the most robust climate predictions possible.
Similar to the NW modeling consortium, decisions could be make by contributing stakeholders

38. Tasks
Acquire or secure sufficient computer resources for regional climate downscaling and to run additional GCM simulations.
Develop GCM filtering approaches.
Acquire CMIP-5 (6) GCM runs and run/acquire additional simulations.
Run large numbers of regional climate simulations

40. Tasks Run applications models (e.g., hydro)
Optimally post-process and combine regional climate simulations to provide robust probabilistic guidance

41. The tasks will be distributed over several groups according to resources/ability
The University of Washington is the largest group and is willing to take on management responsibilities.

42. Products
Model grids and custom products will be available to supporting stakeholders and their designees.
Grids can also be made available to regional climate impacts group (Oregon State, UW CIG, etc.)

43. The END