URBAN POLLUTION MODELING IN WINTER JAPAN EXPERIENCE Toshimasa
Ohara (Shizuoka University) Yuki Otsuka (Shizuoka University) Seiji
Sugata (National Inst. for Environ. Studies) Tatsuko Morikawa
(Petroleum Energy Center )
Slide 2
Background High wintertime concentrations of aerosol particles
are serious atmospheric environment problem in Japan, especially in
the Tokyo Metropolitan Area (TMA). Trends of air quality in Tokyo
Significant improvement Small improvement In the past three
decades, the urban air pollution in Japan has gradually improved
due to a series of emission control. Still however, the TMA
experiences unacceptable air quality with high levels of particle
matter during winter.
Slide 3
Objectives To clarify the mechanism of urban pollution
formation in the TMA, an intensive field study was conducted in
December 1999 covering the TMA by the Japan Clean Air Program
(JCAP)*. These observations were successful in detecting typical
episodes of urban pollution in the TMA during winter. * Japan Clean
Air Program (JCAP), which was launched in 1997 by the Petroleum
Energy Center, in collaboration with automobile and oil industries
in Japan. This presentation focused on the current application
results of regional three-dimensional model to the JCAP field
campaign in December 1999 in order to analyze the formation
mechanism of the heavy air pollution of the aerosol particles and
those precursors in winter in the TMA.
Slide 4
Characteristics of urban pollution in the TMA (1)Complicated
meteorology by terrain complexities The terrain complexities
generate complex local wind circulation such as land/sea and
mountain/valley flows, and these wind circulation system play a
significant role for the urban air quality. (2)Trans-boundary
pollution The trans-boundary pollution from Asian countries
influence urban pollution. (3)Major emission is automobile Major
emission source is related in automobiles likewise in many
mega-cities in the world.
Slide 5
Topography around the TMA Characteristic of the urban pollution
in the TMA (1) The terrain complexities generate complex local wind
circulation such as land/sea and mountain/valley flows, and these
wind circulation system play a significant role for the urban air
quality. Mizuno and Kondo, 1992 Ohara and Uno, 1997 Tokyo Tsukuba
Meso-front Calm Meso-front Strong inversion layer Kanto Plain
Slide 6
Characteristic of the urban pollution in the TMA (2) The
trans-boundary pollution from Asian countries influence urban
pollution. Annual spatial distribution for surface sulfate (g/m 3 )
Average surface aerosols in spring, 2001 Ammonium Nitrate EC
OC
Slide 7
Characteristic of the urban pollution in the TMA (3) Major
source is the automotive emission likewise in many mega-cities in
the world. Emission map around the TMA NOx59% SO 2 25% NMVOC40%
CO90% EC90% OC95% Contribution of emissions related in automobiles
Line sources from automobile emissions
Slide 8
2. JCAP field campaign in winter, 1999
Slide 9
Overview of observations Surface observations Upper
Observations To clarify the mechanism of urban pollution formation
in the TMA, an intensive field study, including aircraft flights
and continuous surface measurements of aerosol mass at 18 sites,
was conducted in December 1999 covering the TMA by the JCAP.
Intensive study days: 7 to 11, December
Slide 10
Time variations for surface NO 2 0600 JST 1200 JST 1800 JST
2100 JST 1500 JST0900 JST 09 December, 1999 10 December, 1999 (a)
Meso-front type (b) Wide stagnation type Meso-front Two typical
pattern of severe pollution (a) Meso-front type Northern part of
the front Stagnation and inversion layer Heavy pollution. Southern
part of the front Strong wind Clean (b) Wide stagnation type Over
the wide area of TMA Weak wind Heavy pollution
Slide 11
Typical heavy pollution episodes 2100 JST 10 Dec., 1999 1800
JST 9 Dec., 1999 airflow SPM airflow Heavy pollution in the wide
area Meso-front Polluted Calm Clean Y K O 1 O 2 F Y K O F Y K O F
Aerosol composition South Front North (a) Meso-front type (b) Wide
stagnation type 75 m height
Slide 12
3. Model and simulation conditions
Slide 13
To simulate the urban pollution in the TMA (1) Complicated
meteorology by terrain complexities Coupled model of RAMS and CMAQ
with horizontal and vertical nesting (2) Trans-boundary pollution
Three nested grids ( East Asia + Japanese Island + TMA ) (3) Major
emission is automobile Emission inventory for automobile source
developed by the JCAP
Slide 14
Model Domains Top of vertical level : 10 km Simulation period :
December 6 to 11, 1999 Evaluation area Tokyo Metropolitan Area
(TMA) Central Japan (Gird2)Kanto Plain (Grid3)East Asia (Grid1)
Height above S.L. (m) 66(x)58(y)20(z) 50(x)50(y)20(z)
40(x)50(y)26(z) 44.8 km (x, y) 11.2 km (x, y) 5.6 km (x, y) 100 m
100 m 20 m
Slide 15
Simulation model Regional Met. Model (CSU-RAMS 4.3) ECMWF Met.
data FDDA Input Parameters SST, Topography 3-D High Frequency Met.
Data Set Chemical Transport Model (CMAQ) Emission Data NOx, SO 2,
CO, NH 3, EC, OC, NMVOC (including biogenic) Boundary
Concentrations Initial Concentrations Gases, Aerosols Grid 1:
Carmichael & Streets (2001) etc. Grid 2, 3 : JCAP
Slide 16
Description of meteorological model CSU-RAMS Ver.4.3 Colorado
State University - Regional Atmospheric Modeling System) Map
projection: Polar-stereographic Vertical coordinate system: z
terrain-following Non-hydrostatic Cloud: Kuo-type scheme Surface
layer: Louis scheme Vertical diffusivity: Mellor & Yamada
scheme (2.5level) Four-dimensional data assimilation: ECMWF Data
Sets (Analysis, Lon.-Lat.=0.5deg, t=6 hours) Two-way nesting
Slide 17
Description of Chemical Transport Model Models-3/CMAQ Models-3
Community Multiscale Air Quality) developed by Byun and Ching
(1999) of U.S. EPA Advection with piece-wise parabolic method (PPM)
Vertical diffusion with K-theory parameterization Deposition flux
as bottom boundary condition for the vertical diffusion Mass
conservation adjustment scheme Horizontal diffusion with scale
dependent diffusivity Carbon Bond 4 (CB-4) chemistry mechanism with
isoprene chemistry QSSA gas-phase reaction solver Emissions
injected in the vertical diffusion module Aqueous-phase reactions
and convective cloud mixing Modal approach aerosol size
distribution and dynamics One-way nesting
4. Results and discussion 4-1 Comparison with observations 4-2
Vertical SPM structure 4-3 Aerosol composition 4-4 OC formation
processes
Slide 20
Observation model Comparison with observations (Meteorological
fields) 12/9 1800 JST 12/10 2100 JST Thin regularly spaced: model
Thicker: observation RAMS with the data nudging using ECMWF
reanalysis data set could reproduce well the meteorological fields
in the TMA through the field campaign. However, it was difficult to
simulate exactly the wind field, for example, the location of
meso-front and the strong stagnant air condition. Calm Meso-front
Calm
Slide 21
Comparison with observations (Air quality) CMAQ with RAMS could
reproduce reasonably well the temporal variations of the observed
concentrations of the aerosol particles and their precursor
gases.
Slide 22
Comparison with observations (SPM distribution) 2000 JST 10
Dec. 1800 JST 9 Dec. ModelObservation Model (1) CMAQ with RAMS
could reproduce reasonably well the observed spatial distribution.
(2) However, the model failed to simulate accurately the high
concentration area and also the simulated concentration tends to be
low. This situation may be explained by Lack of reproduction of the
meteorological field simulated by the RAMS Underestimation of
anthropogenic emissions (3) Especially, it was very important to
reproduce the details of meteorological fields by a meteorological
model.
Slide 23
Comparison with observations (Average particle composition for
two-day period) North (inland) Observation Model South sea The
model can calculate only the fine particles, sulfate, nitrate,
ammonium, EC, and OC. For five fine components, modeled
compositions are almost similar to observations. Model tends to
underestimate the observed concentrations for components except EC.
Contribution of EC and OC to the total particles is very high.
Slide 24
Spatial distribution of SPM L1L1 L2L2 2000 JST 10 Dec. 1800 JST
9 Dec. North Inland South Sea N-S vertical section along the line
LHorizontal (surface) North Inland South Sea PollutedClean Polluted
air mass 50 km 250 m Very shallow by the surface inversion layer.
Flight observation: below 300 m Polluted air mass 100 km 900 m
Flight observation: below 900 m Modeled depth of vertical polluted
layer accorded with the flight observations. Modeled meso-front (a)
Meso-front type (b) Wide stagnation type
Slide 25
Average fine particle composition (for two-day period) Surface
Column (below 2000 m height) Average in a whole domain 34% 17.8%
9.1% 6.4% 15.9% 49.3% 16.1% 19.6% 18.2% 12.0% EC (%)OC (%)SO 4 2-
(%)NO 3 - (%)NH 4 + (%) (1) Percentage of Carbonaceous particles
(EC+OC) is 50% at surface. They mainly caused by the primary fine
particles emitted from automobiles in the TMA. (2) NO 3 - and NH 4
+ percentages around the TMA is higher than that in the TMA.
Slide 26
Average composition of fine particles at surface in the TMA
(for two-day period) (1) Modeled composition is agreement with the
observations except the ratio of EC and OC. (2) At surface, the
total carbonaceous particles content (EC+OC) reaches to 66%. (3) At
aloft, the contributions of carbonaceous particles decrease with
the altitude because the effect of surface emissions is smaller;
instead, the contribution for NO 3 - and SO 4 2- increase because
they are secondary particles.
Slide 27
Average OC components (for two-day period) Primary OC
Anthropogenic Secondary OC Biogenic Secondary OC (POC) (ASOC)
(BSOC) OC g/m 3 At surface, 80% Small fraction (almost 5%) Higher
in the mountainous area; 15% ; important component of OC in this
area despite the low reactivity in winter. TMA
Slide 28
Conclusions (1)RAMS can reproduce qualitatively the
meteorological fields. However, it is difficult to simulate the
exact wind field, for example, the location of meso-front and the
strong stagnation. (2)CMAQ with RAMS can reproduce reasonably well
the particles and gases. However, the model fails to simulate
accurately the high concentration because of lack of RAMS
performance. (3)The local wind systems play an important role in
controlling the formation of heavy particle pollution. Particularly
important factors are the meso-front and the strong stagnant air
condition. (4)The urban aerosol particles near surface in the TMA
are dominated by EC and primary OC. (5)The secondary biogenic
organic carbon is an important OC component despite the low
reactivity in winter.
Slide 29
Next steps Improvement of model performance Important tasks are
To reproduce the details of meteorological field by a meso-scale
meteorological model. To improve the emission inventory, especially
for carbonaceous particles from automobiles. To estimate
uncalculated particles, for example, chloride and coarse particles.
Sharing lots of results and experiences of urban modeling in many
cities over the world in order to improve the urban air
quality