Initial Experiments on Simulation of Windshear and Significant Convection Events using Aviation Model (AVM)Wai-Kin Wong1, C.S. Lau2 and P.W. Chan1

1- Hong Kong Observatory2- Hong Kong Polytechnic University

CMOS 2012 / General NWP-WAF Part 2

29 May 2012 (1E3.2 ID 5345 16:45-17:00H)

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 Systembased on JMA Non-Hydrostatic Model (NHM) and 3DVAR

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

Pearl River Delta (PRD) domain dx = 600 mForecast range = 9 hr

HK Airport (HKA) domain dx = 200 mForecast range = 6-9 hr

HK Airport (HKA) domain dx = 200 mForecast 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)

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

WRF T+4h forecast

Sea-breeze simulation

NHM forecast

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

Headwind profile simulator (HKA-AVM)

WRF T+6 h Forecast

Terrain-induced windshear2009-12-26 21 UTC

LIDAR

NHM Forecast

Surface AWS

HKIA

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

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

Significant convectionPRD-AVM WRF T+4 h forecast

NHM T+4 h forecastN.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)

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

09-18 02:00 UTC 02:30 UTC 03:00 UTC 03:30 UTC

04:00 UTC 04:30 UTC 05:30 UTC05:00 UTC

Simulated maximum reflectivity for model run at 2011-09-17 23:00 UTC

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

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)

And the effect of model tuning

Original “Test3”

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).

Thank you very much