1. Initial Experiments on Simulation of Windshear and Significant Convection Events using Aviation Model (AVM) Wai-Kin Wong 1, C.S. Lau 2 and P.W. Chan 1 1- Hong Kong Observatory 2- Hong Kong Polytechnic University CMOS 2012 / General NWP-WAF Part 2 29 May 2012 (1E3.2 ID 5345 16:45-17:00H)

2. Operational Mesoscale NWP System in HKO 2 Meso-NHM - 10 km horizontal res. - 585x405x50 7.3 - 42.2 N; 89.9-146.6E model top: 22.7 km - 72 hour forecast - 3-hourly update RAPIDS-NHM - 2 km res., 305x305x60 - 19.5 - 25.0 N; 111.2 - 117.1 E - model top: 20.3 km - 15 hour forecast - hourly update Atmospheric Integrated Rapid-cycle (AIR) Forecast Model System based on JMA Non-Hydrostatic Model (NHM) and 3DVAR

3. Development of Aviation Model (AVM) Sub-kilometre resolution NWP to enhance support in aerodrome forecasts and development: Wind and windshear forecast guidance Windshear alerting service Headwind changes encountered by aircrafts under terrain-induced and sea- breeze windshear conditions Forecast techniques on: Significant convection Visibility

4. Pearl River Delta (PRD) domain dx = 600 m Forecast range = 9 hr HK Airport (HKA) domain dx = 200 m Forecast range = 6-9 hr HK Airport (HKA) domain dx = 200 m Forecast range = 6-9 hr HK International Airport  Target completion time for PRD+HKA = 1 hour  Update frequency = 1 hr  Initial and boundary conditions: RAPIDS-NHM (dx=2km)

5. Feasibility Study WRF-ARW (ver. 3.2.1) and JMA-NHM for PRD and HKA domains Estimate computation requirement for running AVM in real-time basis Numerical experiments sea-breeze convergence terrain-induced windshear significant convection low visibility (fog) Performance of two models are similar and WRF-ARW has higher code running efficiency

6. WRF T+4h forecast Sea-breeze simulation NHM forecast

7. Headwind profile “simulator” (PRD-AVM) - Simulated headwind change / windshear “encountered” by the flight during descending

8. Headwind profile simulator (HKA-AVM)

9. WRF T+6 h Forecast Terrain-induced windshear 2009-12-26 21 UTC LIDAR NHM Forecast Surface AWS HKIA

10. Headwind profile simulator (PRD-AVM) - Terrain-induced windshear

11. Headwind profile simulator (HKA-AVM) - Terrain-induced windshear

12. Significant convection PRD-AVM WRF T+4 h forecast NHM T+4 h forecast N.B. model forecast at a time lag of about 1.5 hr on the passage of squall line Late evening thunderstorms and organized convections developed inland and passed over HK (8-9 September 2010)

13. Widespread convection blocking airspace and traffic near HKIA on 18 September 2011 Rapid development of convection over airspace to the south Radar seq. 06:00-16:00 HKT Please refer to 3B2.4

14. 09-18 02:00 UTC 02:30 UTC 03:00 UTC 03:30 UTC 04:00 UTC 04:30 UTC05:30 UTC05:00 UTC Simulated maximum reflectivity for model run at 2011-09-17 23:00 UTC

15. Selecting optimal physics scheme and parameters to simulate sea-breeze convergence and low-level windshear near take-off/landing zone

16. Expt.Model Physics Original (a)CAM LW and SW radiation scheme (b)Eta similarity (used in Eta Model) based on Monin-Obukhov with Zilitinkevich thermal roughness length and standard similarity functions from look-up tables (c)Mellor-Yamada-Janjic PBL (d)“simple” diffusion (gradient term taken along coordinate surfaces) for turbulence and mixing (e)Eddy coefficient option (km_opt) using 2d deformation – horizontal diffusion from horizontal deformation, vertical from PBL scheme Test3 (a)RRTMG LW and SW radiation process (b)MM5 similarity surface layer based on Monin-Obukhov with Carslon-Boland viscous sub-layer and standard similarity functions from look-up tables (c)LES PBL using model computed momentum flux u*, heat flux and moisture flux (d)“full” diffusion treatment (gradients using full-metric terms) (e)km_opt using 3d prognostic equation of TKE (1.5 order TKE closure) “Optimal” physics options (for sea-breeze simulation)

17. And the effect of model tuning Original “Test3”

18. On-going development Sensitivity tests on the physics options and new version of WRF codes Data assimilation techniques to ingest high resolution observations (surface AWS and LIDARs etc).

19. Thank you very much