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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

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monsoon

Dynamical Background

Dynamical Background

anticycloneupper

troposphere

cyclonelower

troposphere

Cyclone at the surface, anticyclone in the upper troposphere

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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

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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

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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

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Earth Jupiter

Persistent anticyclone(Great Red Spot)

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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

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MLS climatology

MLS CO (Jul-Aug) 100 hPa

MLS O3 (Jul-Aug) 100 hPa

anticyclone high CO

low ozone

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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?)

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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

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Asian monsoon

N. American monsoon

HDO enrichmentfrom deep

convection

Water vaporisotopologue HDOfrom ACE-FTS data

MLS H2O

Note differencesbetween Asian and

N. American monsoon

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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

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ACE JJA climatology

monsoonmaximum

minimum for air with recent ocean contact

tropicalminimum

transport tostratosphere via monsoon

Randel et al, Science, 2010

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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?

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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)

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Thank you

ASM-STEworkshop

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Extra slides

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from Larry Thomason and Jean-Paul Vernier

SAGE II satellite observations (cloud cleared; likely due to aerosols)

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WACCM simulation

of HCN

- climatological sources

- parameterized ocean sink

ACEobservations

WACCMmodel

Tracers are simulated well by chemistry transport model

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observations MOZART model

Park et al, JGR, 2009

One day

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CO max over deep convection

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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)

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15 km

CALIPSO satellite lidar cloud observations

Tibet