Red – Flag Workshop Micro – Climate Modelling and Observations Alan Gadian and Ralph Burton

1. Red – Flag Workshop Micro – Climate Modelling and Observations Alan Gadian and Ralph Burton (NCAS/ICAS, Leeds) Red-Flag Workshop 14th December 2011

2. Contents:- • Weather Research and Forecasting Model (WRF). • 2. Application to this case. • Examples of recent work. • Modelling. • 5. External assessor. • 6. Summary. Red-Flag Workshop. 14th December 2011

3. 1. Weather Research and Forecasting Model (WRF) • Used for research and operational forecasting (adopted by Met. Agencies of China, India, Korea, USA, .... ) • Approximately a third of the world’s population get their weather forecast from WRF • Developed by NCAR, NOAA, AFWA, NRL, etc. etc. • Open source and supported for almost all countries • Used for: • Atmospheric physics / parameterisation research • Case-studies • Real-time NWP • Global simulations • Idealised simulations (convection, orographic flow, etc. ) • Data assimilation Red-Flag Workshop. 14th December 2011

4. Courtesy NCAR/MMM • Advantages of WRF: • Easy to learn how to use • Easy to set up new cases • Initialisation data easy to acquire • Written in Fortran/Fortran90 • Wide community support • Free! Red-Flag Workshop. 14th December 2011

5. Warnings: WRF is not perfect • Difficult to determine a priori which combination of boundary layer scheme and land-surface scheme works “best” [ Burton et al. in prep. ] • Sensitivity to microphysics scheme Gallus, W.A. et al. (2008): “Inter-comparison of simulations using 5 WRF microphysics schemes with dual-polarization data for a German squall line”, Adv. Geosci., 16, 109-116 N.B. more schemes added since 2008 • Sensitivity to land-use characterisation [ Pielke, R.A. (2001): “Influence of the spatial distribution of vegetation and soils on the prediction of cumulus convective rainfall”, Rev. Geophys., 39, 2, 151-177 • Sensitivity to all other schemes: not recorded, but known to exist Red-Flag Workshop. 14th December 2011

6. WRF: The advantages:- • Huge number of users and well tested. • It is Eulerian rather than semi-Lagrangian, which although slower than other models, but therein lies its advantage for research work, as it has many conserving properties, is much more flexible, and more suitable for detailed studies. • Two way nesting. Convection and wave motions generated in the inner domains are transmitted to the outer domains, such that the larger scale flow includes the effects of the upscaling of energy. Most atmospheric forecast models are one way nesting (i.e. the flow in the inner domains does not impact on the outer domains). WRF can be run in both one way and two way nested schemes. This is important in this case, to assess any feedback on the outer regions. • Flexible domains (see next slide). • All the explicit convection and flow characteristics can be described in the inner two local domains. • The outer domain of the model is driven by global fields from large scale atmospheric data sets such as those produced by the US National Centers for Environmental Prediction (NCEP) or European Centre for Medium Range Weather Forecasts (ECMWF). Red-Flag Workshop. 14th December 2011

7. Examples of WRF validation I: explicit convection. Observations WRF Weisman et al. 2008: “Experiences with 0-36h explicit convective forecasts with the WRF-ARW model”. Good job of replicating the frequency, longevity, and propagational characteristics of the precipitation episodes. Red-Flag Workshop. 14th December 2011

8. Examples of WRF validation II: large climate-scale runs. NCAR Nested Regional Climate Model (NRCM) from www.nrcm.ucar.edu Red-Flag Workshop. 14th December 2011

9. Application to this case. The four, two way nested domains; with resolutions of ~250m (inner domain) to ~ 30km (outer domain). The model is driven by global data fields) Red-Flag Workshop. 14th December 2011

10. 3. Examples of current work • Antarctic Peninsula airflow • Land based renewables consortia project • Arran Student Summer School • 4. Current simulations on the effect of removing the • Hornisgrinde Ridge (Black Forest). Red-Flag Workshop. 14th December 2011

11. 3.1. OFCAP (Orographic Flow on the Antarctic Peninsula) (Tor Smith) Daily WRF forecasts for Jan. 2011: deciding when to fly Red-Flag Workshop. 14th December 2011

12. 3. 2 Land-based Renewables Project: downscaling ERA40 data to determine the effect of climate change on crops (willow, miscanthus). Test case for Dec. 1961-Feb. 1962 Inner domain (#3 of 3) – 1km resolution Modelled distribution of wind speeds Dec. 1961 – Feb 1962 for 6 AWS sites in Yorkshire, ~6km apart. N.B. different distributions. Outer domain windspeeds during Feb. 1962 storm (9km resolution). 110,000 houses damaged in Sheffield. WRF captures storm very well. Storm seen in tail of distributions Red-Flag Workshop. 14th December 2011

13. 3. 3 NCAS Arran Student Summer School WRF is run daily and a 60-hour forecast is produced. A range of WRF products are given to the students, including: Surface winds and temperatures, Goat Fell Isle of Arran Hill Walk Is it safe to walk up Goat Fell? (2010 – 30m/s winds – dangerous conditions, WRF was vital) Daily forecast of various met. products for Student Field Centre: “Virtual AWS” Red-Flag Workshop. 14th December 2011

14. 3.4. Role of orography in the generation of convection: case study, 20th July 2007 Fig 2A in briefing doc. Real orography lifts the warm, moist air Surface winds and θe 1140Z development of convective cell (shown by outflow.) Fig 2B in briefing doc. Removing orography no lifting, and no develop- ment of convective cell. Surface winds and θe 1140Z Red-Flag Workshop. 14th December 2011 From V. Smith, PhD thesis, 2010

15. 4. Modelling I. • An understanding of the potential impacts of the change in the local orography on the local mircro-climate is required. In particular, any changes to the local air flow, cloud formation and precipitation is required to determine if there is likely to be any adverse impact on the specialised species living within the WHS. Any climatological assessment for the site must therefore include a detailed representation of the local orography and the significant seasonal and interannual variation in the regional climate. . • It is proposed to assess the environmental change in the surface orography and surface properties by excavation of peaks in the Nimba hills to retrieve iron ore by: • using the Weather Research Forecasting Model (WRF) which is a world leading research code. • using a code that can be used to model convection and that can upscale and downscale the important processes that effect the regional climate; • an examination of the regional rainfall probability distribution and the effects on the local climate region climate, over an annual basis, including both the dry and wet season (i.e. consideration of seasonal variations); • modelling the before-and-after changes for existing climate conditions, one El-Niño, one La Niña and two “normal” years, and compare the results (i.e. a consideration of the significant interannual variability which is known to exist); • and production of a flexible and open access modelling tool that can be used at a later date to assess further different scenarios as required. Red-Flag Workshop. 14th December 2011

16. 4. Modelling II. • For the basic model configuration, assuming all the model set up had been agreed and the computer hardware had been set up, the computing would take approximately 6 months to complete. • The deliverables would be an agreed list of meteorological output variables such as rainfall probability distributions, number of days with rainfall, rainfall maximum and minimums, convective activity, cloud base data (which can be produced for domains 1, 2 and 3). • These data would be analysed by meteorologists and atmospheric scientists to assess the impact on the local micro-climate of the proposed mining excavations. These data would need to link to the ecologists overseeing any potential impacts to biodiversity etc. Red-Flag Workshop. 14th December 2011

17. 5. External Assessor:- We suggest that Dr Greg Holland, NCAR, be the external Reviewer. Dr Holland was director of the NCAR Earth System Laboratory, (NESL), and is now leading a large project on regional climate modelling. He is a leading international figure in Earth System Modelling, and was until recently Head of the Meso-scale and Micro-scale Modelling (MMM) division at NCAR. He is a member of the WMO Expert Committee on Hurricanes and Climate Change, a senior researcher in the Willis Research Network and chair of the NCAR Regional Climate Prediction Program. Red-Flag Workshop. 14th December 2011

18. Summary • WRF is a state-of-the-art numerical weather prediction problem. • The PIs have extensive experience of its use, from climate-scale • runs to high-resolution case studies. • PIs have worked on orographic flows, convection, and African • meteorology. • Computer time required is approximately 6 months on ~256 processor • machine. • This will allow a suite of 8 before-and-after runs. Years to be determined. • Which met. variables are required? - Red-Flag Workshop. 14th December 2011

19. DATA --- NIMBA Weather station Red-Flag Workshop. 14th December 2011

20. SAMS DATA SUPPLIED • History of observations • The first observations date back to 1979 with the parameter rainfall. In 1993, the observation of other parameters began. This year has seen the opening year of the Station. From then until 2006 the observations are daily observed at 08h, 12h and 18h. • Inventory data • The following parameters were recorded: • The rainfall makes up most of the information available with records of missing data at certain times of the series 1979-2006 (no record from 1986-1992!). • The minimum daily temperatures are available from August 1993 to September 1999 with series sometimes discontinuous. • The maximum daily temperatures are available on the August 1993-May 2004 with discontinuities. • The relative humidity, cloudiness, wind to 12 (of 16 Pink direction and speed in meters per second) and evaporation are available intermittently for the period August 1993 to December 2006. Red-Flag Workshop. 14th December 2011