Lecture 5: Monsoon circulations in the UTLS

• Dynamics and transport in the Asian monsoon anticyclone• chemical variability linked to the monsoon• instability and eddy shedding• transport to stratosphere• eruption of Mt. Nabro in June 2011
• Water isotopes in the UTLS

anomalous chemistry
clouds/aerosols
transport to stratospherepersistent anticyclone
deep convective
transport

HadleycellWalkercellDynamical Background
Cyclone at the surface, anticyclone in the upper troposphere
one-day‘snapshot’
July 10, 2003

anticyclone
uppertroposphere

Randel and Park, 2006, J. Geophys.
Res.
Hoskins and Rodwell, 1995
Highwood and Hoskins, 1998

cyclonelowertropospherePark et al., 2009, J. Geophys. Res.

Anticyclones in the Upper Troposphere
geopotential height and winds 100 hPa

anticyclones

Note thatthe anticyclone
does not lie
on top of thedeep convection

Convection (heating)heating

Matsuno-Gill Solution
Park et al., 2007, J. Geophys. Res.

Anticyclonic circulation extends into lower stratospherebalanced dynamical structure

cold tropopause
and lower
stratosphere

Upper troposphere
coldH

tropopause

warm
Lower troposphereLwarm
troposphere

Randel and Park, JGR, 2006

Confinement within the anticyclone:
idealized transport experiments• initialize 2400
particles inside
anticyclone• advect withobserved winds
for 20 days

• test differentpressure levels

Randel and Park, 2006, J. Geophys. Res.

transport
simulation
at 150 hPa

day 0

day 10large fraction
remain inside
anticyclone

Randel and Park, 2006, J. Geophys. Res.

day 20tests at different pressure levels show that confinement
mainly occurs over altitudes with strongest winds

Randel and Park, 2006, J. Geophys. Res.

Frequent tropopause-level cirrus clouds in monsoon region

CALIPSO cloud fraction near 16 km

CALIPSO satellite lidar cloud observations

20 km

15 km

July 14, 2010Tibet

Monsoon aerosol layer near 16 km

16 km

SAGE II measurements 1999-2005
Thomason and Vernier, ACP, 2013

CALIPSO measurements
Vernier et al , GRL, 2011
Narrow layer
near tropopausestrong chemical influence on summer UTLS

MLS 100 hPa
carbon monoxide (CO)variability
linked tomonsoon
convection

Park et al, JGR, 20082007, 2009

ACE Fourier Transform Spectrometer

ACE occultations, 2004-2006

All observations for June-AugustLow latitudes: 4 samples / year
Randel et al., 2012, J. Geophys. Res.

ACE measurements JJA 2004-2006

ACE CO(16.5 km)

MLS CO (100 hPa)max

ACE HCN (16.5 km)

High CO and HCN are
associated with the Asianmonsoon anticyclone
Park et al., 2007, J. Geophys. Res.

Park et al., 2008, Atmos. Chem. Phys.

ACE-FTS CO Profiles

all profiles 10°-40° N

inside vs. outside
Inside anticyclone

outsideenhancement
inside theanticyclone
up to ~20 km

other tropospheric tracers

= 2

=5

=1.5

=0.5
lifetime inmonths

C2H2 measurements from ACE-FTS satellite
photochemical lifetime ~ 2 weeks

evidence of relatively rapidtransport to the UTLS

C2H2/CO ratio ~ measure of photochemical age

C2H2/CO20

relatively young air
inside theanticyclone,
up to ~17 km

1510

olderyounger

Aircraftmeasurements

Enhanced CH4
within anticyclone

ACP, 2011
acetylene C2H2

benzene C6H6

Age of air estimated from short-lived hydrocarbons

Result: air is relatively young: ~5-12 days

Baker et al, ACP, 2011

chemical transport models can simulate observed large-scale behaviorMLS observations

MOZART simulation

Park et al, JGR, 2009

simulation for one day
100 hPa

MLS observations

MOZART simulation

Park et al, JGR, 2009

Vertical structure of CO from model simulation

dynamical ‘edge’ ofanticyclone

Questions:• How sharp is the ‘chemical edge’?
• When and where does air ‘escape’ the anticyclone?

Transport pathways derived fromobservations and models
confinement by anticyclone+ transport to stratosphere

Transport above 200 hPa
by convection / circulation

convective transport(main outflow near 200 hPa)

Park et al, JGR, 20082007, 2009surface emission(India and Southeast Asia)

Key points:•Asian monsoon anticyclone is dynamical response to monsoon convection (heating)•Climatological feature every year ~June-September•cold tropopause, frequent clouds, aerosol layer•Strong chemical anomalies inside anticyclone, due to: Rapid transport from surface (evidenced by short-lived chemical species) Circulation traps air inside anticyclone

What happens
to the outflow
from deep
convection?

3D trajectories
initialized at 200 hPa
in regions ofdeep convection
OLR < 160 K+ 10 days
confinement
within anticyclone+ 20 days
from Hella Garney

Comparison of trajectory calculations with MLS CO climatology
Colors: MLS COclimatology

Black contours: trajectory calculations

Three-dimensional diabatic trajectories

Transport upand down!

Note: this is work in progress, and not well understood yetMonsoon circulation is inherently unstable

Hsu and Plumb 2000 JAS‘eddy shedding’ frommonsoon circulation

time-independent
divergence forcing

Anticyclone viewed in potential vorticity
relatively low PV

JGR 2013

PV in monsoon region at 360 K

May 1 – September 30, 2006

Day 1 = May 132 June 162 July 1
93 Aug 1
123 Sept 1

Garny and Randel, 2013, J. Geophys. Res.

32

Dynamical variability echoed in tracers
PV at 360 K

CO from Aura MLS

June 10

June 10

June 12June 12June 14June 14

Garney and Randel, 2013, JGR

Another example
PV at 360 K

CO from Aura MLS

August 28

August 28

August 30

August 30

September 1

September 1

Garny and Randel, 2013, J. Geophys. Res.

Transport to the stratosphere via the monsoon anticyclone••

HCN – biomass burning tracer
Minimum in tropics (ocean sink)
Long lived in free atmospheremonsoon
maximumtropicalminimumtransport tostratosphere
via monsoon

minimum for air withrecent ocean contact
35

JJA
WACCM
simulationof HCN- climatologicalemission sources

ACE- parameterized
ocean sink

WACCM

Seasonal cycleof HCN
from ACE-FTS

maxima persist instratosphere becauseof long HCN lifetime

Africa andS. America
biomassburning

HCN ‘tape recorder’ from ACE-FTS measurements

JGR, 2013

boreal summer maxima from
Asian monsoon circulation

Key points:•Trajectory studies valuable for understanding fate of convective outflow•Fundamental instability of anticyclone: eddy shedding•HCN provides evidence for monsoon transport to stratosphere

39

Eruption of Mt. Nabro

June 13, 2011

Eritria, Africa

Red Sea

Nabro eruption
June 14, 2011

SO2 plume from Nabro

SO2 plume from Nabro

SO2 plume from Nabro

SO2 plume from NabroPrimary eruption was to middle / upper troposphere (~10-16 km)(and small amount to stratosphere, above 18 km)

westward movementfor 17.5 km and above

trajectories forJune 13-16

trajectories overlaid
with GOME SO2Bourassa et al, 2012

Stratospheric aerosols from OSIRIS satelliteNabroeruption
June 13-14

Bourassa et al, 2012

June 21

July 1

July 6

July 11x

Bourassa et al, 2012

July 16

July 21

July 26

July 31OSIRIS aerosol extinction

eruption June 13

Interpretation:•Nabro SO2 plume in upper troposphere, transported aroundmonsoon circulation to eastern side.
•Transport to stratosphere through monsoon circulation (and convection?)•Confined to anticyclone, converted to stratosphericsulfate aerosol ~ 1 month•Further evidence of transport to lower stratosphere via monsoon(Nabro in right place at right time)
June 17

July 6

SO2Bourassa et al., 2012, ScienceJuly 1734 daysafter eruption

Bourassa et al., 2012, Science

Nabro aerosols
20 km
15 km

Ongoing research:•What are the contributions of different chemical source regions
to the upper troposphere? Is reactive chemistry important?
How much reactive nitrogen is in the anticyclone?
•When and where does air escape the anticyclone? Are there
sharp gradients across edges?
•What is the role of deep convection vs. large-scale upward
circulation to the stratosphere? How important arediurnal variations in convection?
•What is the nature of the tropopause aerosol layer? Does it
influence UTLS clouds?

Extra slides

200 hPa streamfunction JJA
JAS 1995

observations

diabatic heating from reanalyses

reasonableagreement

linear model with heating

Result: heating from convection
mainly forces monsoon anticyclone

July 1: 18 days after eruption

Also enhanced water vapor in monsoon regions
North Americanmonsoon
Asianmonsoon

white contours: deep convection

Anticyclone viewed in potential vorticity

Garny and Randel, 2013, J. Geophys. Res.

57

PV in monsoon region at 360 K

May 1 – September 30, 2006

Day 1 = May 1
32 June 162 July 1
93 Aug 1
123 Sept 1

Garny and Randel, 2013, J. Geophys. Res.

58

Global variations of Water Vapor Isotopes
from ACE-FTS satellite data

Water vapor isotopes: H2O16, HDO, H2O18, H2O17

Key point: heavier isotopes are preferentiallydepleted as water changes phasevalues often expressedin delta notation:‘per mil’What do we expect to see for water isotopes in the stratosphere?

Brewer, 1949

Answer: preferential depletion ofheavier isotopes, as air
is slowly dehydrated on
passing the cold point tropopause
Very small HDO/H2OBut observations show a different story:
persistent increase in TTL region, heavy stratosphere
past observations‘heavystratosphere’

RayleighMoyer et al 1997
Hanisco et al 2007
Fueglistaler et al, 2009

But observations show a different story:
persistent increase in TTL region, heavy stratosphere
past observationstransport of ice inovershooting deep convection ?
‘heavystratosphere’

RayleighMoyer et al 1997
Hanisco et al 2007
Fueglistaler et al, 2009

ACE-FTS water isotopologues
FTS measurements: 2.2 – 13.3 μm
5+ years of data (Feb. 2004 – present)~ 3,500 occultations /year
All major isotopologues of water and methane
Resolution: ~300 km horizontal, 3 km vertical

ACE occultations, 2004-2009

Data presented here:~20,000 occultations(entire V2.2 dataset 2004-2009)
3-month seasonal averages DJF, …
(~ global coverage)
Randel et al 2012

Low latitudes: 4 samples / year

ACE-FTS dD profiles show similarities to previous measurements
persistent increase in TTL region, heavy stratosphere

Nassar et al, JGR 2008

Climatologies
for March-May

H2O

Global behavior derived from ACE-FTSdDHDO

Note HDO ~ 10,000 times
smaller than H2Overy difficult measurement!

increase due
to methaneoxidation

max depletion near
global tropopause

Seasonal variation of dD

TTL minimum
below tropopause
minimum in winterhemisphere

PDF of ACE-FTS in the tropics

Rayleighcurves

vertical coordinate
is H2O; similar behavior
for altitude coordinateTropical seasonal structure (15o N-S)

ACE verticalresolution

cold point
tropopause••

minimum below tropopause
strongest depletion in February

Randel et al., 2012, J. Geophys. Sci.

Tape recorder and seasonal cycle in H2O, HDO

H2O

Note:
only 4 monthsof data per year

HDO

Randel et al., 2012, J. Geophys. Sci.

H2OdDseasonal minimum below tropopause(convection, not temperature)
Randel et al., 2012, J. Geophys. Sci.

monsoonsignallittle evidence oftape recorder in dD

MIPAS satellite observations

H2O
Note these results arevery different fromPayne et al 2007
analysis of MIPAS data

this is very different
from ACE-FTS resultsdD
verticalresolution
6-8 km?

dD – corrections for methane oxidation
Conservation of H:

Conservation of D:(H2 + H2O + 2*CH4) = const.

(HD + HDO + CH3D) = const.

Observations + models:

D HDO = - D HD – D CH3D= -4.5 * 10-4 (CH4 – CH4entry)

D H2O ~ -2.0 * (CH4 – CH4entry)

CH4from
ACE

CH4entry

aircraft observations
McCarthy et al,2004, JGR

dD – corrected for methane effects

using ACE CH4

Seasonal cycle of methane-corrected dD

monsoonsignal75

Longitudinal structure and ACE-FTS sampling
14.5 km

DJFJJAclimatologicaldeepconvection

dD at 16.5 km

isotopically depletedair close to
deep convection

DJFMAMJJASONDistinct behavior of Asian, NA summer monsoon regions

Very different dD

Similar H2O patterns
over Asian, NA monsoons

Persistent behavior:vertical profiles overAsian, NA monsoons
for different years

Relevant physics: depth of overshooting
convection, into unsaturated stratosphere(e.g. Dessler and Sherwood, 2004)

Clouds andthermodynamic
profiles overmonsoons

Asia monsoon

N. America monsoon
highersaturation
over Asianmonsoon

cloudfraction

Caveat:CALIPSO misses
late afternoon
deep convection

Asian monsoon signal in HCN

monsoon signal in dD(comes mainly from N America)
ACE dD JJA

isotopesignalmainly fromN. America

Asianmonsoon
maximum
Randel and Park, 2006, J. Geophys. Res.

HCN maximum
from Asian monsoon

Key points:• Isotopic increase of water vapor above TTL is supported in ACE data
- convective overshooting and/or mixing from extratropics ?
• Significant spatial structure to global seasonal cycle of dD- spatial variability tied to convection- convection has different effects in different places(tied to background thermodynamic structure)• Strong enhancement associated with N America summer convection.
- persistent signal, leads to NH-SH asymmetry in stratosphere• Curious lack of tape recorder signal in dD

Things we don’t understand:• What causes the seasonal variation in tropical dD?
(max. depletion during NH winter)• Why is there a shift in max. TTL depletion towards winter hemisphere?
(is this related to ACE-FTS sampling?)• How does tropical variability couple with monsoon signal, so that
there is little vertical propagation in the tropics(lack of ‘tape recorder’)?

Mechanisms for the increase of dD above tropopause:
1) Convective ice lofting

Simulation by Max Bolot, LMD

2) Mixing from extratropics

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