+ Best Practices in Regional Climate Modeling Dr. Michel d. S. Mesquita Bjerknes Centre for Climate Research, Uni Research

+ Quality assurance

+ Definition “…the maintenance of a desired level of quality in a service or product, especially by means of attention to every stage of the process of delivery or production” (Warner 2011, BAMS)

+ Lack of quality assurance Not enough training and experience Disregard or lack of care when considering an appropriate model setup and selection of parameterization schemes “demands for quick results” Warner (2011, BAMS) Are models being “used wisely”?

+ Warner’s 14 Steps to Success

+ Warner’s recommendations: ① Define the scientific or practical objective of your study ② Identify and develop a physical understanding of the atmospheric processes that must be simulated ③ Analyze all available observations ④ Prepare an experimental design plan Warner (2011, BAMS)

+ Warner’s recommendations: ⑤ Define the appropriate horizontal and vertical resolutions of the model ⑥ “Avoid the tendency to prematurely run the model, before the above-listed steps have been completed” Warner (2011, BAMS)

+ Remember this: “…the sooner that the model is run, the longer a study will take” One should avoid “the temptation to run the model before thoroughly understanding the prevailing meteorology…” Warner (2011, BAMS)

+ Warner’s recommendations: ⑦ Allow for spin up of the physical processes ⑧ Test the domain size Warner (2011, BAMS)

+ Warner’s recommendations: ⑨ Review the literature and prepare sensitivity studies ⑩ Understand that there are limitations to any model simulation 11 Prepare a verification plan Warner (2011, BAMS)

+ Warner’s recommendations: 12 Be well organized and keep a journal or log. Keep also your computer scripts and key model output files 13 Make use of good coding practices 14 Try to use open-source software Warner (2011, BAMS)

+ Activity (15 minutes) Activity (15 minutes)

+ WRF Project You have received funding to develop an early warning system for your country with respect to tropical storms Activity: Using Warner’s 14-step approach, discuss with your group how you could prepare and create such a system. NASA satellite image of tropical storm Nate. Masters, J. (2011) Tropical storms and hurricane roundup. URL:

+ Designing a Numerical Experiment: Best Practices Designing a Numerical Experiment: Best Practices

+ Domain Size How large does the domain need to be? It will depend on the application Simulations for a few days: Initial Conditions Simulations for a few months, or years: Boundary Conditions Domain sizes should not be too small: no less than 100x100 points Where should the lateral boundaries be placed? Avoid steep topography Away from the region of interest Wang, W. (NCAR), URL:

+ Warner (2011)

+ Vertical resolution How many vertical levels should be used? At least 30 or more levels Vertical grid distance should not be larger than 1000 m If finer horizontal grid size is used, consider increasing the vertical resolution Wang, W. (NCAR), URL:

+

+ Nests Warner (2011)

+ Nests When should nests be used? Input data resolution is coarse Save computing resources Remember: The nest domain size should not be too small The nest boundary should be kept away from the coarse domain boundary, and steep topography. Wang, W. (NCAR), URL:

+ Input Data Familiarize yourself with your input data: how good are the data? Forecast data Reanalysis data Climate model data How frequent should the boundary conditions be? As frequent as possible Wang, W. (NCAR), URL:

+ Model Options Where should you start? What do other people have success with? Check the literature - references, papers Use simple options first: For example, Graupel may not be important if dx >> 10 km mixed layer ocean model may not be needed Use analyses from weather centers before trying to create your own dataset for both initial and lateral boundary conditions Wang, W. (NCAR), URL:

+ Be Pragmatic! Model results can be affected by many choices: Domain configuration, both horizontal and vertical Input data; Lateral boundary conditions. The model has limitations: Physics: biases, may not handle certain process well Wang, W. (NCAR), URL:

+ Thank you!