ANALYSIS OF INFLUENCE OF METEOROLOGICAL CONDITIONS ON
SUMMER OZONE LEVELS OVER CENTRAL KANTO AREA
関東地方におけるオゾン濃度と気象条件の関連分析
Background➢ Both NOx and NMHCs emission are decreasing, but ground O3 concentration is increasing. It is believed that is due
to increase of trans-boundary from East Asia, particularly in spring (Ohara, 2007).
➢ However, in summer, it is not clear yet how steady the increasing trend is.
500

8040050040y = 1.0358x + 40.682
R2 = 0.4742

3090 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05
Year02005199719951993

1991

2019891001985

Annual average pollutants during 1990 2005 in the Tokyo area

1987

201050

2003

20060

2001

30Maximum ozone

70

1999

40

300

NMHC (ppbC)

Ozone and NOx (ppb)

60OzoneNOx
NMHCO3 concentration (ppb)

70

Years

Long term changes in daily maximum O3
concentrations in summer in Tokyo area

Seasonal variation of ozone (Ohara, 2007)

Investigate the factors that affect O3 levels is very helpful for better
understanding variations in ozone concentrations in summer

Objectives of research➢ Apply multiple-scale numerical model for assessing environment issues➢ Investigate the effect of meteorological conditions on O3 levels in summer over the central Kanto area
➢ Analyze formation process of high O3 levels in summer over the central Kanto area

Methodology➢ Numerical simulation using the MM5/CMAQ modelling system➢ Statistical analysis using a multiple regression analysis

Description of a numerical model
Analysis area andconfiguration

MM5 model

EMISSION DATA (2000)

The Fifth-Generation NCAR / Penn
State Mesoscale Model
Calculating
wind, temperature, pressure, etc.

Prepared by Central Research Institute ofElectric Power Industry, Tokyo, Japan
IncludingCO2, NOX, VOC, SO2, NH3, etc.

FDDA
NCAR Met. Data:
T, U, P, RH, SST,
Topography ,Land Use, etc.

Hour emission data at 14:00 JST (mole/s/grid)

CMAQ model (EPA, USA)
Table 1： Analysis size domains and grid
resolution

The Community Multi-scale Air Quality modelingSize (X[km]x Y[km])Grid number

resolution
(km)

D1

450x54051x61x23

9D2

216x26173x88x23

3

D3

99x120100x121x23

1

Initial andboundary
conditionstransport

chemistry

depositions

cloud,
precipitation
aerosols

JCAP

Chemical/physicalprocesses:
MM5/CMAQ Default

SpeciesICsNE
BCs W
SO3
28282528

NO
2.0
2.0
2.0
2.0NO2
4.0
4.0
4.0
4.0

ALD
1.8
1.8
1.8
2.0

FORM
2.2
2.2
2.2
2.4

ETH
1.4
1.4
1.4
3.2

OLE
1.6
1.6
1.6
4.2

Default (USA)

TOL
14.4
14.4
14.4
11.4

XYL
0.6
0.6
0.6
0.7

ISO
0.5
0.5
0.5
0.5

PAR
74.3
74.3
74.3
82.7

Air quality
concentration
O3, NOx, CO..

Model evaluation (for Nerima, Tokyo)
NerimaNerima450Wind Direction (degree)

Wind Speed (m/s))

108642360
270
18090008/4

8/5

8/6

8/4

8/5

8/6
LocalNerimaTime (JST)15012034

Ozone (ppb)

Temperature (℃)

38

Local NerimaTime (JST)3026229060
30

180
8/4

8/5

8/6

8/4

Local Time (JST)

8/5

Local Time (JST)8/6

 Statistical measures
Variables

Mean Bias

Mean Error

Root Mean Squared
Error

Correlation
CoefficientWind speed (m.s-1)

0.8

0.9

1.0

0.6

Wind direction(degree)

-6.0

35.6

56.2

0.6

Temperature (oC)

1.6

1.7

1.9

0.9

Ozone (ppb)

4.7

13.8

17.0

0.9

Investigating relationship between
the meteorological conditions and O3 levels in summer
 Urban heat island (UHI) - O3 concentration

The peak O3 - meteorological conditions
Daily maximum ozone (ppb)

75
70

34
33

Ozone
Temperature

3265

31

60

30

55

2950

28

45
40

2735

2630

25

Daily maximum temperature(oC)80

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05
YearTemp & Wind at 12:00 JSTOzone at 14:00 JST

The effect of urbanization on air pollution

Observed values (ppb)Long-term changes in daily maximum O3 in the Tokyo area anddaily maximum temperatures at Nerima (Tokyo) in the summer
706560555045O3  O3T TU U
 0.80  0.49 , O3TU

403530R  0.91,a) 1997a) 2-m Temperatureb) 1997-1987b) 10-m wind velocity
Simulated results of case1997 minus case 1987 at
12:00 JST.

a) Daytime average(7:00~18:00 JST)R 2  84.1

30

40506070
Values calculated by the regression equation (ppb)
The observed seasonally averaged daily maximum O3 for summer in theTokyo area plotted against those predicted by the regression equation

The areal percentage
of urban land-use➢ About 84.1% of the long-term variation of theThe results imply that:
averaged daily maximum ozone during 1985-2005 may
High stagnant
Increases inbe accounted for by changes in daily maximum
conditions
urbanization
temperature and averaged wind speedb) Nighttime average(19:00~24:00 JST)
Surface O3 of case 1997
minus case 1987.

Increasing ozone
levels in summer

Process analysis of ozone formation under different
weather conditions over the central Kanto Area
These physical and chemical processes which effect ion O 3 formation
can be described in mass conservation equations as follows:Cit         C     C     C 


i
i
i
K
K
K




  x uC i   y vCi   z wC i 
 ADV   x  x  x   y  y  y   z  z  z DIF

  Ci   Ci   Ci   Ci 
 CHEM  (1)
i  t  DDEP   t WDEP   t CLOUD   t  AEROSOLS

Where: C is the concentration of ozone; u, v, and w are the componentof the velocity vector; K is the eddy diffusivity; ADV is advection process;DIF is diffusion process; CHEM is the net rate of chemical production;
DDEP, WDEP, CLOUD, and AEROSOLS are rate of change ofconcentrations due to dry deposition, wet deposition, cloud, and aerosol,
respectively
 Using MM5/CMAQ model , authors quantify the contribution ofthe different physical and chemical processes to high O3 levelsADV
DIF
DDEP
CHEM
O3

50

1000

800

Height (m)0600b)O3CHEM
DDEPDIFADV

Flow chart of weather pattern classification; P1, P2, P3,and P4 are sea level pressures at Choshi, Maebashi,
Oshima and Onahama, respectively.

400100100

Pattern I-50ADV
DIF
DDEP
CHEM
O3

200

0-100-80 -60 -40 -20

1471013Local time (h)161922020

40

60

80

O3 (ppb); process rate (ppb/hr)

Diurnal variations of ozone concentrations and rate of change in O3
concentration due to different processes for Nerima, Tokyo in August,
2005: (a) within the first vertical layer of the model; and (b) within thelower atmosphere at 14:00 JST.
 Comparison of various weather patterns in August 2005: High O3
levels are controlled by three main weather patterns as shown in left sidefigure. Patterns I and II are regular summertime pressure patterns with afrequency of occurrence of 26% and 16%, respectively. Compared withPatterns I and II, Pattern III is an irregular pressure pattern in summer, andthe number of occurrence is small. The contribution of the different
components to O3 with various weather patterns are shown in bottom figure.

Process rate (ppb/hr)

Process rate (ppb/hr)

a)

500

Process rate (ppb/hr)

100

Pattern IIADVDIFDDEPCHEMO350

0-50-50-100-100

1

4

71013
Local time (h)

16

19

22

1

4

7

10
13
Local time (h)

16

1922

Diurnal variation of the rate of change in ground-level ozone concentrations due tothe different processes for the two weather patterns at Nerima, Tokyo.

➢ it can be suggested that the significant decrease in ozone removal dueto the chemical and advection processes under conditions of higherstagnation (Pattern II and III) is the most important reason for theenhanced levels of ozone in the central region of Tokyo.