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)

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

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

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

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

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

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

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

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

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