AIR POLLUTION – MONITORING MODELLING AND HEALTH

30
Air Pollution – Monitoring, Modelling and Health
wind coming from the south-east. Figure 15(b) shows that until 1300LT, the time with the
highest solar radiation, the maximum quantity of O 3 is formed. At this time, wind is divided
in three main convergences which divide the plume of O 3 into two different small plumes.
Two O 3 maxima are formed at this time on 7th Feb, 140 ppb and 150 ppb, for the northern
and north-western parts of the city, respectively. Then, until 1400LT the wind direction is
the same wind direction than at 1300LT. However the wind speed is very strong (two times
stronger than at 1300LT), which pushes rapidly the O 3 plume to go up to the north and
north-west of the city. Fig .15(c) shows that at 1500LT the plumes leave the basin of HCMC
through the north and north-west. The O 3 concentrations remain low in the city. Then, at
2000LT the wind direction is the same wind direction than at 1000LT. At 2000LT, there is not
solar radiation coming to the earth which prevents O 3 production and promotes the
destruction of O 3 , especially in the north-western part of the city.
QT
QT
TD
TD
TN
TS
ZO
TN
TS
ZO
DO
D2
DO
D2
HB
HB
BC
BC
(a)
(b)
QT
QT
TD
TD
TN
TS
ZO
TN
TS
ZO
DO
D2
DO
D2
HB
HB
BC
BC
(c)
(d)
Fig. 15. Map of O 3 concentrations (ppb) at ground level in the domain of 34 km x 30 km, at
10LT00 (upper left panel), 1300LT (upper right panel), 1500LT (lower left panel) and
2000LT (lower right panel), 7th Feb 2006 and measurement stations. The different colours
are the O 3 levels.