1. Interannual variability of transport via the Asian Summer Monsoon
Giorgio S. Taverna1, W. Feng1, R. Pope1,M. Chipperfield1 and P. Forster1
1 Institute for Climate and Atmospheric Science, University of Leeds, UK
EGU Assembly 2017
24th April 2017
EU StratoCLim project

2. Outline Background → Asian Summer Monsoon transport
→ EU Stratoclim Campaign
→ TOMCAT 3D off-line chemistry transport model (CTM)
Methodology
→ Simulations using artificial tracers
Results
→ Accumulation over Monsoon region
→ Vertical structure of the transport
→ Interannual variability of the tracers over the ASM anticyclone
Conclusions and future work

3. Asian Monsoon as a pathway to the UTLS
Background
Asian Monsoon as a pathway to the UTLS
Several works both observational and modelling have proven the ASM circulation to be an effective pathway for climate relevant species to enter the UTLS.
CO, August 2005
JA 2005 average MLS CO, 100 hPa c
CO mixing ratio distribution from WACCM on August 2005 at 100 hPA ( Pan et al., 2016).
Horizontal structures of July–August 2005 average MLS carbon monoxide and water vapour, at 100 hPa . NCEP horizontal wind fields are shown as vectors (Park et al., 2007)
CO, 6 July at 380 K level
JA 2005 average MLS H20, 100 hPa
CLaMS CTM CO mixing ratio ( Ploeger et al., 2015).

4. EU Stratoclim Campaign 2016-2017
Background
EU Stratoclim Campaign
New in-situ has been obtained in the Asian Monsoon Area by a campaign based in Greece in 2016 with a high altitude research aircraft carrying an innovative and comprehensive payload.
The next phase of the campaign is planned to start in August 2017 from Katmandu (Nepal) and should last 8 weeks, with about 10 measurement flights.
M55 Geophysica aircraft (image courtesy of Ralf Weigel)

5. The Asian monsoon anticyclone
Background
The Asian monsoon anticyclone
The Asian summer monsoon (ASM) circulation develops a strong anticyclonic vortex in the UTLS spanning from East Asia to the Middle East.
The anticyclone is a region of persistent enhanced pollution in the upper troposphere during boreal summer.
The Asian Monsoon circulation(courtesy of Yong Wang, FZJ Jüelich)

6. The Tropical Upper Troposphere Lower Stratosphere (UTLS) region
Background
The Tropical Upper Troposphere Lower Stratosphere (UTLS) region
Region of the atmosphere between 13 and 22 km (Gettelman et al., 2011).
Simplified structure of the UTLS. The dashed line represents the level of zero radiative heating (LZRH). The grey band is the Tropical Tropopause Layer (TTL) and (a) indicates the deep convection outflows (Fueglistaler et al., 2009).

7. Background
TOMCAT Off-Line CTM
Three-dimensional (3D) off-line chemical transport model (CTM) flexible vertical coordinate which can use both σ-p and σ-θ levels.
The model uses winds and temperatures from meteorological ECMWF re-analyses to specify the large-scale atmospheric transport and temperatures.
Simplified chemistry schemes used here.
Variable horizontal resolutions: 2.8o x 2.8o (moderate), 1o x 1o (high), 60 vertical levels from 1000 hPa to 0.1 hPa.

8. Background
High resolution CO simulations for the StratoClim campaign : Greece 2016
1st flight
Filaments of Western part of the anticyclone at the southern edge of the flight path
TOMCAT - Criogenically Operated Lader Diode (COLD) data 1st flight comparison

9. Simulations using artificial and real tracers
Methodology
Simulations using artificial and real tracers
A moderate horizontal simulation (2.8o x 2.8o ) was run which included CO25, CO50 and two artificial tracers, TR5 and TR50, with parameterized loss rates and lifetimes.
Computationally inexpensive and fast: appropriate for long runs
ERA-interim updrafts used as convection scheme
CO25, CO50, TR5 and TR50 tracers have lifetime of 25, 50, 5 and 100 days, respectively.
CO25 and CO50 use realistic monthly and spatially varying estimates of the surface CO emissions, along with specified idealised loss rates.

10. Accumulation over the Monsoon region :1985-2000
Results
Accumulation over the Monsoon region :
Simulations show maxima values over the monsoon region for both idealized CO25 and CO50 for JJAS at 150 hPa over the period
surface
surface
CO25
CO50
150 hPa
150 hPa

11. Accumulation over the Monsoon region:1985-2000
Results
Accumulation over the Monsoon region:
TR5 and TR50 are constrained at the surface with a constant 100 ppbv mixing ratio between 32N-49N.
surface
surface
TR5
TR50
150 hPa
150 hPa

12. Vertical structure of CO25 , 1985-2000
Results
Vertical structure of CO25 ,
The vertical cross sections E show that CO25 in the ASM region is enhanced throughout the troposphere up to 390 K.
area

13. Vertical structure of TR5 1985-2000
Results
Vertical structure of TR
The vertical cross sections of TR5 show that the westerly circulation associated with the anticyclonic circulation (green solid contours)acts as barrier for the vertical transport. Associated (fast) transport appears only around 30N
area

14. Interannual variability of the tracers over the anticyclone
Results
Interannual variability of the tracers over the anticyclone
The transport in the anticyclone shows variability at several time scales
These plots show example of interannual variability of CO25 at 150 hPa

15. Interannual variability of the tracers over the anticyclone
Results
Interannual variability of the tracers over the anticyclone
The interannual variability of the JJAS anomalies of the tracers has been calculated at 100,150 and 200 hPa levels in the core of the anticyclone
area

16. Interannual variability of the tracers over the anticyclone
Results
Interannual variability of the tracers over the anticyclone
The interannual variability of the JJAS anomaly of CO25 over the the core of the anticyclone doesn’t appear to be strongly related to the strength of the ASM, defined as rainfall intensity anomalies.
Flood years
Drought years
Core of the anticyclone at 150 hPa

17. Interannual variability of the tracers over the anticyclone
Results
Interannual variability of the tracers over the anticyclone
The interannual variability of the JJAS anomaly of artificial tracer TR5 over the core of the anticyclone shows same “chaotic” relation at 100, 150 and 200 hPa as for CO25.
Flood years
Drought years
Core of the anticyclone

18. Conclusions and future works
The model results show peaks of the mixing ratio in the ASM anticyclone for CO25, CO50 in JJAS while for artificial TR5 and TR50 tracers the confinement is less evident.
No clear correlation is found between the JJAS rainfall intensity anomalies over all-India and accumulation anomalies at 100,150 and 200 hPa
Further investigations will be done to try to correlate the interannual variability of the transport with El Nino, La Nina’s features and large volcanic eruptions.
More appropriate emission of artificial tracers will be set to discern the different transport mechanisms.
The model data will be compared with satellite and StratoClim data, when available.