Improvement of Air Quality 

Improvement of Air Quality 

in Hong Kong in Hong Kong 

by Using MM5 Coupled w

by Using MM5 Coupled w

Huang J.P., Fung J.C.H., Huang J.P., Fung J.C.H., 

Zhang Y., Zhang Y.,

Lau A.K.H., Kwok R. and Lo J.F.L. Lau A.K.H., Kwok R. and Lo J.F.L.

Hong Kong University of Science and Tech

Hong Kong University of Science and Tech

North Carolina State University North Carolina State University
z The objective of this research is to b

understand and predict the atmosph(in particular, within the Planetary BLayer ~ 1 to 2 km) and air quality othe Pearl River Delta.

z Different dispersion models (SAQ

CMAQ) has been used in this study

Objective
Features of Pearl River De

Features of Pearl River De

From HK

H

H

S

S

Guang Zhou Guang Zhou

Macau

z Located in Southern Chinaz 41,700 km

2 in size, 50 million in population

z Major cities: Hong Kong, Shen Zhen, Guang Zhou anz Rapid economic and industrial growth; high air pollu
Meteorological Features of P

Meteorological Features of 

z Complex terrain, coastal, and land-use chz Sub-tropic climate

– Synoptic scale: Meiyu, Typhoon, Monsoon– Local scale: Land-sea breeze, Urban heat isl

Monthly number of days with ( Visibility reporting < 

Days / month

Visibility Report (11/1976 
Aerosol Optical Depth - Column sum of aerosol co
Number of non Number of non-comp

comp

hourly AQO ( hourly AQO (red) (from 

(from 

Yuen Long Yuen Long

O3 problem problem

Tsuen Wan

Sham Shui Po

Tung Chung

Central/Western Central/Western
O3 problem in HK: epis

problem in HK: epis

major contributors to air pollution episodes: major contributors to air pollution episodes: O3

O3 : the biggest contributor : the biggest contributor 
Sea breeze circulat

Sea breeze circulat
Land-sea breeze circulation c

sea breeze circulation c
Meteorological Model

Create Physical Atmosphere

Solve full set of atmospheric 

equations for evolution of wind, 

temperature, pressure and moisture 

content, etc. 

(MM5 v3.6)

Atmospheric Chemistry Mode

Chemical reactions of various chemical spe

and solve the advection-diffusion equation

(SAQM)

Emission

Anthropogen

(EMS

PATH Model Syst

PATH

Pollutants in the ollutants in the Atmosphere and their tmosphere and their Tr

r

Hong Kong ong Kong (HKEPD, 1997) (HKEPD, 1997)
Domain c Domain configurations of onfigurations of MM

26 sigma levels (mm515 sigma levels (SAQ
MM5 Model Configurations MM5 Model Configurations

40.5km, 13.5km 4.

Cumulus Grell PBL MRF Moisture Simple ice Radiation RRTM 

3⁄4 MM5 v3.63⁄4 4 nested Domains: 

3⁄4 40.5 km (115x75), 13.5km (85x73) , 4.5km (85x7

3⁄4 2-ways nesting3⁄4 26 full sigma levels (~10 levels below 1km)

3⁄4 Physical parameterization schemes

(for the unresolved scales)
MM5 Model Configurations 

3⁄4 Up-to-date fine resolution 

(as fine as 30 m) is applied to 

and PRD (i.e. both D3 and D4)

3⁄4 Initial and Boundary Con

NCEP Global Final Analyses 

(http://dss.ucar.edu/datasets/ds0
Rapid development over PRD during the 

Rapid development over PRD during the 

1993 

1993 

Land use

map
1994 USGS 

Percentage of each land-use classification 

innermost domain:

Urban area: increase from 0.5% to 12.9%Cropland: decrease from 45.6% to 22.7%
Land Surface Model 

Land Surface Model 

 NOAH community land-surface soil hyd

which was jointly developed by the 

3⁄4

National Centers for Environmental Prediction (N

3⁄4

Oregon State University

3⁄4 the U.S. Air Force 

3⁄4 the Office of Hydrology 

 Coupled mode; the scheme is fully intera MM5 simulations of surface radiation, p

near-surface winds, humidity, and tempethe external forcing for the land surface

 The Noah-LSM provides surface sensible 

heat flux and skin temperature as lower condition to MM5

 Heat and moisture fluxes are then proces

scheme and transported to the atmosphe

Refinements in Noah Refinements in Noah

-LSM ex

LSM ex

Green vegetation fraction definition

3⁄4 Problems caused by interpolating the 18km AVHR

domains (4.5km, 1.5km)

3⁄4 Landuse based green vegetation is used in the inner 

3⁄4 PRD located in subtropics, seasonal variation is very 

Landuse based Sea value = 
Refinements in Noah Refinements in Noah

-LSM ex

LSM ex

1. Up-to-date landuse map for PRD 2. Better green vegetation fraction in in3. Enhancements of urban landuse trea

Noah-LSM 

3⁄4 Simply modifying the values of physical p

urban landuse – albedo, roughness length, properties and evaporation 

4. Modification of MRF PBL scheme 

3⁄4 Better methods for computation of free con

turbulence, PBL height and surface heat fl(Liu Y., F. Chen, T. Warner, S. Swerdlin, J. Bowers, and S. Halvorson, 2


200

200
Surface Observation

backgr

sea breeze

Refined LSM D

Surface wind verificationvalid at 2003/10/31 2pm
Comparison of velocity Comparison of velocity

TC

TC

MM5-STD

MM5-LSM
Results Results

Urban heat island
Surface Temperature from M

20031031 2am (mid-night

HK

GuangZhou
8:00pm 

Temperature variant: T - m

Surface Temperature from MODIS

20031031 2am (mid-night)

NEW
8:00pm 

Temperature variant: T - m

Surface Temperature from MODIS

20031031 2am (mid-night)

OLD
Temperature Profiles Comparison Temperature Profiles Comparison
Surfa
Surfa
Surfa
Surfa
Surfa
Surfa

D

1993 landuse
D

2004 landuse
Meteorological Model

Create Physical Atmosphere

Solve full set of atmospheric 

equations for evolution of wind, 

temperature, pressure and moisture 

content, etc. 

(MM5 v3.6)

Atmospheric Chemistry Model

Chemical reactions of various chemical species

and solve the advection-diffusion equations

(SAQM)

Emission

Anthropogen

(EMS

PATH Model Syst
Introduction of PATH: E

Introduction of PATH: E

EMS-95: The US Emission Modeling Sy3⁄4 Point sources

(power plants and industrial sources)

3⁄4 Mobile sources

(road vehicles, railways and aircrafts)

3⁄4 Area sources

(domestic and commercial fuel combus

3⁄4 Shipping sources

(marine traffics) 

3⁄4 Biogenic sources

(vegetation)
Typical ground level emission r

NOx 

VOC
NOx 

Typical ground level emission 

VOC
Meteorological Model

Create Physical Atmosphere

Solve full set of atmospheric 

equations for evolution of wind, 

temperature, pressure and moisture 

content, etc. 

(MM5 v3.6)

Atmospheric Chemistry Model

Chemical reactions of various chemical species

and solve the advection-diffusion equations

(SAQM)

Emission

Anthropogen

(EMS

PATH Model Syst
SAQM Model Configur

3⁄4 SAQM: the 

SARMAP 

Air 

Quality 

Mod

modified for its application to PATH in H

3⁄4 4-nested domains: 40.5, 13.5, 4.5, 1.5 km 

cells for each domain;

3⁄4 CB-IV chemical mechanism is used;

diffusion: horizontal-briggs; vertical-eddies;horizontal advection: 4th order Botts scheme;

3⁄4 78 thermal-kinetic reactions, 11 photolyt

56 reactive species,

31 output species (15 for gas and 16 for p
An O3 episode: episode: (22-24 Octob

24 Octob
Model resu

Model resu

SAQM simulation: standard MM5

SAQM simulation: MM5-LSM
CMAQ simulation: standard MM5

CMAQ simulation: MM5-LSM
Summary and Concl

Summary and Concl

 The simulations of MM5 with NOAH LS

better agreement with meteorological obsuch as surface winds and temperature p850 hpa, etc., than those of MM5-STD, in with observations;

 The surface ozone simulations have been 

terms of the peak ozone and spatial patteMM5/NOAH LSM is used to generate mfields for air quality models;

 However, the impact of MM5/NOAH LS

modeling is still under investigation. 
Acknowledgements Acknowledgements

 Thank the Hong Kong Enviro

Protection Department for the of PATH model and air qualitthe Hong Kong Observatory fof meteorological data.