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Overview of the Asian monsoon anticycloneand influence on the UTLS
Bill RandelAtmospheric Chemistry DivisionNCAR Earth System Laboratory
Thanks to: Mijeong Park, Laura Pan, Louisa Emmons,
Doug Kinnison, MLS team, ACE team
What is the monsoon anticyclone, and why is it interesting?
• dominant circulation feature of NH summer UTLS
• forced by deep convection over India and Bay of Bengal
• associated with local maxima in trace constituents (water vapor, ozone, pollutants)
• active region for stratosphere- troposphere coupling
deep convection
monsooncirculationnear 16 km
monsooncirculationnear 16 km
carbon monoxidenear 16 km
MLS satellite data
Seasonal cycle of lower stratosphere H2O
summer monsoonmaximum
LH
Antarcticdehydration
HALOE instrument onUARS satellite 1992-2005
summertime lower stratospheremaxima linked to
Asia and North American monsoons
H H
L
Rosenlof et al 1997Jackson et al 1998Dethof et al 1999
Likely contribution to water vapor entering stratosphere:
Bannister et al, 2004; Gettelman et al, 2004; Park et al, 2004; Fu et al, 2006
Climatological precipitation in NH summer
6
monsoon
Dynamical Background
Dynamical Background
anticycloneupper
troposphere
cyclonelower
troposphere
Cyclone at the surface, anticyclone in the upper troposphere
7
atmosphere response to steady tropical heating (Gill, 1980)
longitude
imposed heating
latitude
symmetric Rossby gyreswest of heating
Kelvin waveeast of heating
Highwood and Hoskins (1998)
Upper troposphere
Lowertroposphere
anticyclones
cyclones
conv
div
idealized vertical structure
9
Convection, heating
Anticyclones in the UT
anticyclones
Convection (heating)
‘Gill-type’ Solution10
observations
Note thatthe anticyclonedoes not lieon top of thedeep convection
geopotential height and winds 100 hPa
Lower troposphere
Upper troposphere
H
L
cold
warm
Randel and Park, JGR, 2006
Dynamical Background
Anticyclonic circulation extends into lower stratosphere
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tropopause
warmtroposphere
cold lowerstratosphere
Cold, high tropopause linked to frequent cirrus
frequent cirrusnear tropopause
Cloud fraction near 16 km
13
Potential vorticity at 360 K (~12 km) AIRS water vapor at 360 K
Anticyclone is regionof low PV
July 10, 2003
High H2O confinedinside anticyclone
Confinement within the anticyclone:idealized transport experiments
• initialize 2400particles insideanticyclone
• advect withobserved windsfor 20 days
• test different pressure levels
Idealized transport simulation at 150 hPa
day 0
day 10
day 20large fractionremain insideanticyclone
Confinement within region of strongest winds
17
Earth Jupiter
Persistent anticyclone(Great Red Spot)
18
Transport linked to the anticyclone:
• Chemical structure observed by satellites
• Transport pathways diagnosed from MOZARTchemical transport model (Mijeong Park)
• Coupling with the stratosphere
MLS observations of CO
Global coverage ~ 1 day
~4 km layer centered near 16 km
enhanced CO mixing ratio in anticyclone
MLS CO (Jun/2/2005) 100 hPa
19
MLS climatology
MLS CO (Jul-Aug) 100 hPa
MLS O3 (Jul-Aug) 100 hPa
anticyclone high CO
low ozone
20
Synoptic variability
MLS CO (100 hPa) 100 hPa CO linked to monsoon convection
CO
OLRproxy for
convection
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Park et al, JGR, 2007
Transport pathways
CO surface emission
(India and South China)
convective transport
(main outflow near 200 hPa)
confinement by anticyclone(transport to
stratosphere?)
22
Transport above 200 hPaby large-scale circulation
(+overshooting convection?)
Diagnosed fromchemical transport modelPark et al, JGR, 2009
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Asian monsoon
N. American monsoon
MLS H2O
24
Asian monsoon
N. American monsoon
HDO enrichmentfrom deep
convection
Water vaporisotopologue HDOfrom ACE-FTS data
MLS H2O
Note differencesbetween Asian and
N. American monsoon
25
Anticyclonic circulationcontributes to large-scaletransport to/from tropics
Kanopka et al, ACP, 2010
MLSobservations
CLaMSsimulation
Also:
Dunkerton, 1995Chen, 1995
isentropic summerstrat-trop exchange linked to anticyclone
Hydrogen cyanide (HCN)
DJF JJA
tropical minimum:air with recentocean contact
ACE HCN 13.5 km ACE HCN 13.5 km
max mi
n
HCN source: biomass burning HCN lifetime: ~4 years in free atmosphere, but sink from contact with ocean
Observations fromACE-FTS satellite
Transport to the stratospherevia the monsoon anticyclone
27
ACE JJA climatology
monsoonmaximum
minimum for air with recent ocean contact
tropicalminimum
transport tostratosphere via monsoon
Randel et al, Science, 2010
28
Complementary perspectives of CO vs. HCN
CO lifetime ~2 months HCN lifetime ~4 years
tropicalminimum
notropical
minimum
Key points:
• Asian monsoon circulation provides effective vertical transport and chemical confinement in UTLS anticyclone (region of chronic pollution)
• CTM with climatological sources and large-scale meteorology shows reasonable agreement with satellite observations
• Observations of HCN suggest monsoon transport to stratosphere - especially effective for Asian pollution (SO2, NOx, other)
Key points:
• Asian monsoon circulation provides effective vertical transport and chemical confinement in UTLS anticyclone (region of chronic pollution)
• CTM with climatological sources and large-scale meteorology shows reasonable agreement with satellite observations
• Observations of HCN suggest monsoon transport to stratosphere - especially effective for Asian pollution (SO2, NOx, other)
Hofmann et al. 2009propose increases dueto Chinese SO2 increases
stratosphericaerosol
Outstanding issues:
• Very few aircraft/balloon measurements in anticyclone (so far)
• How important is convective overshooting vs. large-scale transport? How does the diurnal cycle influence convective transport?
•What is the detailed behavior of convective and cirrus clouds? Are aerosols observed? If so, what optical properties? (absorbing?) What is the radiation balance near the tropopause?
•What is the detailed structure across vortex edge? (e.g. filamentation?) What are important exchange mechanisms across edge?
• What active chemistry is occurring? Do aerosols nucleate and grow?
•What controls interannual variability? How will anticyclone evolve in a changing climate?
32
12 noon 3 pm 6 pm
Tibet plateau convectionin late afternoon
CALIPSO, Cloudsatobservations at 1:30
convective cloud statistics from3-hour geostationary (CLAUS) data
Blue = deep, high convective clouds
(Motivated from Jonathan Wright, Rong Fu)
33
Thank you
ASM-STEworkshop
34
Extra slides
35
from Larry Thomason and Jean-Paul Vernier
SAGE II satellite observations (cloud cleared; likely due to aerosols)
36
37
WACCM simulation
of HCN
- climatological sources
- parameterized ocean sink
ACEobservations
WACCMmodel
Tracers are simulated well by chemistry transport model
38
observations MOZART model
Park et al, JGR, 2009
One day
39
CO max over deep convection
40
215 hPa
Model vs. observations
Park et al, JGR , 2009
MLS water vaporMLS H2O (Jul-Aug) 100 hPa
MLS H2O (Jul-Aug) 216 hPa
max inside the anticyclone
max over deep convection
41Park et al, JGR, 2007
100 hPa
216 hPa
(level ofconvective
outflow)
42
15 km
CALIPSO satellite lidar cloud observations
Tibet