Transport of halogenated VSLS from the Indian Ocean to the stratosphere through the Asian monsoon circula:on

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Priscilla Brooks
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1 Transport of halogenated VSLS from the Indian Ocean to the stratosphere through the Asian monsoon circula:on Alina Fiehn Helmke Hepach, Elliot Atlas (RSMAS), Birgit Quack, Susann Tegtmeier, Krüger (UiO) ACAM Workshop,

Measured bromoform (CHBr3) concentra@on in the surface oceans (Ziska et al.

2 Asian monsoon transport to the stratosphere Tropospheric pollu:on JJA Oceanic halogen containing very short lived substances (VSLS, life:me <0.5 a)? Measured bromoform (CHBr3) in the surface oceans (Ziska et al. 2013, ACP) HCN from ACE satellite (Randel et al. 2010, Science) Are oceanic VSLS entrained via the Asian monsoon circula:on? 2

3 Suggested VSLS transport Stratosphere Tropical Tropopause Layer (TTL) How much Halogen loading reaches the stratosphere? Troposphere LiYing by deep Asian monsoon transport How fast is the transport? Ocean VSLS emissions VSLS emissions CHBr 3 CH 2 Br 2 CHCHBr 3 I 3 CH 2 Br 2 CH 3 I 17 d 150 d d d 150 d 3.5 d How much is emiued? 3

4 OASIS cruise Bromoform (CHBr3) emissions July and August 2014 West Indian Ocean Trace gas measured in air and water every 3 h Emissions calculated F = k ΔC Strong source region for VSLS. Elevated at coasts, banks and in upwelling regions 4

FLEXPART Lagrangian transport model with convec@on scheme Input: 6 hourly ERA- Interim fields Forward or backward trajectories Output every 6 hours for 3

5 FLEXPART Lagrangian transport model with scheme Input: 6 hourly ERA- Interim fields Forward or backward trajectories Output every 6 hours for 3 months Simula:ons Stohl et al Bromoform emissions from OASIS cruise 10,000 forward trajectories from measurement sites Atmospheric life@me profile for emiued VSLS 2. General transport from Indian Ocean Forward trajectories from 1 x1 grid over West Indian Ocean surface 1404 trajectories released every day in July Source regions of monsoon an:cyclone Backward trajectories from 1 x1 grid at 17 km 27,000 trajectories released on July 31 st,

ERA Interim input Geopoten@al anomaly and horizontal winds at 100

July 2014 down up Strong an@cyclone in July at 100 hpa Upward

6 ERA Interim input anomaly and horizontal winds at 100 hpa velocity and July 2014 anomaly at 100 hpa July 2014 down up Strong in July at 100 hpa Upward movement above Bay of Bengal, Tibetan Plateau, Southeast Asia, and China 6

7 1. Simula:on: OASIS OASIS transport regimes Subtropical westerlies Monsoon Tropical 10 day forward trajectories 7

8 1. Simula:on: OASIS Entrainment of bromoform at 17km Subtropical westerlies Monsoon Tropical Low efficiency of transport (0-1%) High efficiency of transport ( 2%) Highest efficiency of transport ( 3%) More than in the Equatorial Atlan@c (1 %) but less than in the West Pacific (3-10 %, Tegtmeier et al. 2012). 8

2. Simula:on: Indian Ocean Entrainment of air

forward trajectories from the Indian Ocean

convec@on 20 day forward trajectories Main

9 2. Simula:on: Indian Ocean Entrainment of air masses Release from the sea surface 10 day forward trajectories from the Indian Ocean Stratospheric entrainment at 17 km oumlow 7.2 % Trajectory distribu@on at 17 km July 2014 convec@on 20 day forward trajectories Main entrance region to the stratosphere is above India, Bangladesh, and Myanmar. Median age: 35 days 9

3. Simula:on: An:cyclone An@cyclone at 17 km

10 3. Simula:on: An:cyclone at 17 km Release at 17 km 10 day backward trajectories Boundary layer source regions July 2014 July 2014 Time needed from boundary layer to 17 km 70% from boundary layer. 48% origin from oceanic boundary layer, 52% from land. Median age: 25 days 10

11 3. Simula:on: An:cyclone Oceanic source regions Oceanic boundary layer source region, July 2014 entrainment from Bay of Bengal and West Pacific is even greater than from Tropical West Indian Ocean. 11

12 Conclusions Tropical Indian Ocean is a strong source region for VSLS. Monsoon transport is fast enough for VSLS from the Indian Ocean to reach the stratosphere. 50% of the tropospheric air masses in the an@cyclone have oceanic boundary layer source region. Expected high entrainment from Bay of Bengal during Asian monsoon season. 12

13 temperature

14 Indian Ocean transport Month of release Run Reach 17 km Median age [d] June % 28.5 June % June % 14

15 source regions Month in 2014 Boundary layer Land Ocean Arabic Sea Bay of Bengal West Pacific Middle America July August September

16 Emissions and entrainment Campaign Ocean Mean CHBr 3 emissions (pmol m - 2 h - 1 ) Mean CHBr 3 entrainment OASIS West Indian nmol 2-3 % TransBrom Open West Pacific nmol 3-10 % SHIVA Coastal West Pacific nmol 5-10 % DRIVE Northeast Atlan@c nmol 2 % MSM 18-3 Equatorial Atlan@c nmol 1 % 16

CLaMS simulations of transport of young air masses to the top of the Asian monsoon anticyclone and beyond

Mitglied der Helmholtz-Gemeinschaft CLaMS simulations of transport of young air masses to the top of the Asian monsoon anticyclone and beyond Bärbel Vogel, Rolf Müller, Gebhard Günther, Reinhold Spang,