1. Ozone variations over the Northern subtropical region revealed by ozonesonde observations in Hanoi Shin-Ya Ogino, Masatomo Fujiwara, Masato Shiotani, Fumio Hasebe, Jun Matsumoto, Thuy Ha Hoang and Nguyen Thi Tan Thanh
Introduction (1)
Latitudinal distribution
of ozonesonde stations
緯度帯別オゾンゾンデ観測点数
Important to observe 3-dimensional distribution and its temporal variation on the global basis
No continuous ozonesonde observation so far over the Indochina Peninsula
Hanoi, Vietnam (20N, 105E)

2. Introduction (2) EQ 20N 15 30 成層圏 Jet NP
Hanoi, Vietnam (20N)
Located near the northern edge of TTL
Suitable for observation of the mass exchange.
Expected seasonal variation in UTLS from north-south shift of zonal mean field
Summer: northward shift  Low amount of ozone
Winter: southward shift High amount of ozone EQ
20N 15 30
成層圏
Jet NP
troposphere
Stratosphere
UTLS
Hanoi

3. Observation and data SOWER Observation at Hanoi Monthly observation
From Sep 2004, for ～8 years
Once or twice/month
Campaign observation
Every winter from 2004/2005
One of the SHADOZ stations
Also used
Aura/MLS Ozone
NCEP Reanalysis 2
OLR

4. 7-year mean seasonal variation of ozone mixing ratio
1) UTLS region: Minimum in winter
2) Ozone increase in pre-monsoon season

5. Seasonal variation: difference between UT and LS
18km
14km

6. Winter (Jan) MLS O3 & Back trajectory Height, U, V, OLR LS
Above tropopause UT
Below tropopause

7. Late spring (May) MLS O3 & Back trajectory Height, U, V, OLR LS
Above tropopause UT
Below tropopause

8. Summer (Jul) MLS O3 & Back trajectory Height, U, V, OLR LS
Above tropopause UT
Below tropopause

9. Meridional distribution
Tongue-shape extension
above the tropopause
Intrusion from
mid-lat stratosphere
below the tropopause

10. Summary
Continuous ozonesonde observations in Hanoi, Vietnam for about 8 years
Described ozone variations in UTLS region (14―20 km)
Seasonal variation in ozone
Winter min and spring-summer max
Different from that expected from north-south shift of zonal mean structure
Both in winter and summer, monsoon-related horizontal transport by the Rossby response to the convective heating
In spring-summer, different processes dominate above and below the tropopause
Above tropopause: tongue-shape extension due to anti-cyclonic monsoon flow
Below tropopause: Intrusion from the mid-lat stratosphere by tropopause folding