Understanding Convective Coupling in Atmospheric Tropical ...
Transcript of Understanding Convective Coupling in Atmospheric Tropical ...
Science Review 12-14 May 2015 Boulder, Colorado
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
Juliana Dias
Understanding Convective Coupling in Atmospheric Tropical Waves
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
Why study convectively coupled tropical waves?
• tropical waves control local weather;
• larger scale tropical waves (such as MJO and ER) affect higher latitude weather;
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2 days
96 days
Westward & symmetric
modes
Eastward & symmetric
modes
our focus is on synoptic-to-planetary waves that are coupled to rainfall
How to diagnose convectively coupled tropical waves?
Kelvin waves
MJO Equatorial
Rossby waves
TRMM (obs)
Ref: Jaramillo, Dias and Kiladis (in prep.)
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
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2 days
96 days
Westward & symmetric
modes
Eastward & symmetric
modes
Kelvin waves
MJO Equatorial
Rossby waves
TRMM (obs)
How well do models resolve tropical waves?
Ref: Jaramillo, Dias and Kiladis (in prep.)
GISS CFSv2
ECGEM CAM4
CMIP5 (models)
CMIP5 representation of tropical waves is not uniform
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
Science Review • Boulder, CO • 12-14 May 2015 5
2 days
96 days
Westward & symmetric
modes
Eastward & symmetric
modes
CMIP5 representation of tropical waves is not uniform
Kelvin waves
MJO Equatorial
Rossby waves
TRMM (obs) GISS CFSv2
ECGEM CAM4
CMIP5 (models)
Why do models have a difficult time representing tropical waves?
Ref: Jaramillo, Dias and Kiladis (in prep.)
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
CMIP5 representation of tropical waves is not uniform Science Review • Boulder, CO • 12-14 May 2015 6
2 days
96 days
Westward & symmetric
modes
Eastward & symmetric
modes
Kelvin waves
MJO Equatorial
Rossby waves
TRMM (obs) GISS CFSv2
ECGEM CAM4
CMIP5 (models)
Why do we care about tropical waves?
• To better understand multiscale tropical-extratropical interactions
• To improve both weather and climate predictions
Ref: Jaramillo, Dias and Kiladis (in prep.)
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
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(1) How sensitive are synoptic scale waves to cumulus parametrizations and the basic flow?
Ref: Dias et al., 2013 JAS/ Dias and Kiladis, 2014 GRL
• Convective coupling induced by Betts-Miller types of cumulus parameterizations have different impacts synoptic scale tropical waves.
lon (°)
time (
days)
(b) MRG div
0 50 100 150 200 250 300 3500
5
10
15
-6 -4 -2 0 2 4 6x 10-3
time
(day
s)
(b)
0 30E 60E 90E 120E 150E 180 150W 120W 90W 60W 30W 00
5
10
15
20
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06
(a) KW amplitude
(b) MRG amplitude
Time (days)
longitude (deg)
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(a)
frequ
ency
(cpd
)
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(b)
-10 0 10
200
400
600
800
1000
(c)
pres
sure
(hP
a)
S0°
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(d)
frequ
ency
(cpd
)
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(e)
-10 0 10
200
400
600
800
1000
(f)
pres
sure
(hP
a)
S90° E
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(g)
frequ
ency
(cpd
)
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(h)
-10 0 10
200
400
600
800
1000
(i)
pres
sure
(hP
a)
S180°
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(j)
frequ
ency
(cpd
)
planetary zonal wavenumber-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(k)
planetary zonal wavenumber-10 0 10
200
400
600
800
1000
(l)
pres
sure
(hP
a)
S90° W
U (ms-1
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(a)
frequ
ency
(cpd
)
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(b)
-10 0 10
200
400
600
800
1000
(c)
pres
sure
(hP
a)
S0°
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(d)
frequ
ency
(cpd
)
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(e)
-10 0 10
200
400
600
800
1000
(f)
pres
sure
(hP
a)
S90° E
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(g)
frequ
ency
(cpd
)
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(h)
-10 0 10
200
400
600
800
1000
(i)
pres
sure
(hP
a)
S180°
-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
(j)
frequ
ency
(cpd
)
planetary zonal wavenumber-16 -12 -8 -4 0 4 8 12 16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8(k)
planetary zonal wavenumber-10 0 10
200
400
600
800
1000
(l)
pres
sure
(hP
a)
S90° W
U (ms-1
Zonal wind (ms-‐1) Zonal wave number
Freq
uency (cpd
) Freq
uency (cpd
)
Pressure (h
Pa)
Pressure (h
Pa)
• Wave scales are not too sensitive to vertical shear
moister drier
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(2) Are multi-scale interactions key to the existence and propagation of the MJO?
Ref: Dias, Tulich and Kiladis, 2011 JAS / Dias et al., 2012 GRL
• There is no systematic enhancement of synoptic scale variability within the MJO envelope
MJO1 … MJO100
cycl
es p
er d
ay
MJO events from 1979 to 2012
1.25d
20d
(a) Eastward power-‐spectrum
(b) Westward power-‐spectrum
Is there a paJern of higher frequency disturbances that is common to most MJO events?
10/01 10/10 10/20 11/01 11/10 11/20 12/01 12/10 12/20 01/01 01/10 01/20 02/01 02/10 02/20 03/01 03/10 03/200
1
2
3
4
10/01 10/10 10/20 11/01 11/10 11/20 12/01 12/10 12/20 01/01 01/10 01/20 02/01 02/10 02/20 03/01 03/10 03/200
1
2
3
4
(a) DYNAMO
(b) TOGA COAREOMI amplitude
MJO amplitu
de
Mme
MJO events
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
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(3) What defines the MJO? Zonal wind or Convection?
• OMI is a useful index for tracking the MJO
convective envelope, including its seasonal changes;
• OMI produces robust statistics of MJO
primary events; and • OMI is available at:
http://www.esrl.noaa.gov/psd/mjo/mjoindex/
Ref: Kiladis et al. 2014, MWR
• RMM and OMI are both bivariate MJO
indexes. RMM is primarily a zonal wind based index, and OMI is an OLR-only index.
Phase 2 Indian Ocean Phase 3 Phase 2 Indian Ocean Phase 3
RMM (zonal wind) OMI (OLR)
2015 2015
JAN FEB MAR APR JAN FEB MAR APR
Phase 7 Western Pacific Phase 6 Phase 7 Western Pacific Phase 6
Phase 1 W
H/Africa Ph
ase 8
(a) EOF1 Jan, 15
(b) EOF1 Jul, 15
OM
I EO
F pa
tter
ns
N O A A R E S E A R C H • E S R L • P H Y S I C A L S C I E N C E S D I V I S I O N
Summary and Conclusions
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(1) Both cumulus parameterization and basic flow impact tropical waves in different ways, highlighting differences in the physical processes underlying their convective coupling.
Is that why it is so difficult to represent tropical waves in models?
(2) Because the MJO does not organize higher frequency waves it is possible that model resolution is not critical to the MJO representation; MJO representation in models might be possible in a coarse resolution global model. (3) OLR based indexes are an important target for model development because they better track the MJO convective envelope. A model can have high MJO skill based on a circulation index without properly representing MJO rainfall.