The Precipitating Cloud Population of the Madden –

Julian Oscillation over the Indian and West Pacific Oceans

Hannah C. Barnes

Dynamics Seminar

24 January 2013, University of Washington, Seattle, Washington

What is the Madden-Julian Oscillation?

Madden and Julian 1972

• Episodic convective burst• Along equator• Indian Ocean -> dateline• 30-90 day period• Boreal Winter• Deep baroclinic circulation

MJO in Indian and West Pacific Oceans

Wheeler and Hendon Index (2004)

•EOF analysis of 200 and 850 hPa zonal winds and OLR

•Two PC time series • 8 phases • Significant MJO

1

2

3

4

5

6

7

8OLR and 850 hPa Winds

Importance of the MJO

Lin et al. 2006

MJO and Pacific Northwest

Precipitation rate anomalies

More precipitation, floods when convection near

dateline

Floods in Western Washington (Bond and Vecchi 2003)

MJO StructureConvectively coupled Kelvin and Rossby waves

Eastward ~ 5 ms-1

Air-sea interaction

Rossby Wave Kelvin WaveRui and Wang 1990

Houze et al. 1980

MESOSCALE CONVECTIVE SYSTEMS (MCSs)

Tropical Cloud Population

Importance of Cloud

Population

• Models unrealistic without including shallow convection (Zhang and Song 2009)

• MJO sensitive to deep and shallow heating (Haertel et al. 2008)

Entire population

No shallow

Satelliteobs.

Zhang and Song 2009

Objectives

• Variability of precipitating clouds in MJO using TRMM Precipitation Radar

• Associated humidity and wind shear

TRMM Satellite Instrumentation

Kummerow et al, 1998

λ= 2 cmImportant! PR measures 3D structure of radar echoes

Data and Methodology• TRMM PR

• 2A23 (rain type classification)

• 2A25 (attenuated corrected reflectivity)

• ERA-interim reanalysis

• 1999 – 2011, October – February, Wheeler and Hendon Index > 1

• Bootstrapping

TRMM orbit

Geographic Regions

Central Indian Ocean Southeast West Pacific

Identify each contiguous 3D echo objectseen by TRMM PR

Convective component Stratiform component

Extreme characteristicContiguous 3D volume ofconvective echo > 30 dBZ

Top height > 8 km

“Deep convective core (DCC)” Horizontal area > 800 km2

“Wide convective core (WCC)”

Extreme characteristicContiguous stratiform echo

with horizontal area > 50 000 km2

“Broad stratiform region (BSR)”

TRMM PR Identification

“Isolated shallow echo (ISE)”Echo top > 1 km below freezing level and separate from deeper convection

Houze et al, 2007, Romatschke et al. 2010, Rasmussen and Houze 2011, Zuluaga and Houze 2013

Central Indian Ocean (CIO) Analysis

The MJO in the CIOTransition to Active 1

2

3

4

5

6

7

8

Active

Transition to Suppressed

Suppressed

Isolated Shallow Echoes

90E60E10S

0

10N

%

Frequency (%)

MJO Phase

20 samples (blue), average (black), and 99% confidence interval (red)

Deep Convective Cores

MJO Phase

%

Frequency (%)20 samples (blue), average (black), and 99% confidence interval (red)

0.025

Broad Stratiform Regions

%

MJO Phase

Frequency (%)20 samples (blue), average (black), and 99% confidence interval (red)

MJO Precipitating Cloud Population

250

• All cloud types vary significantly • ISE suppressed, 2 phases after active• DCC, WCC, and BSR simultaneous active

• Areal variability - BSR dominate• Number variability

• ISE dominate• WCC > DCC > BSR

x10^4ISE DCCWCC BSR

%

MJO PhaseMJO Phase

x104

Large-Scale Relative Humidity

MJO Phase

Frequency (%)

Relative Humidity (%)

Solid lines = active, dashed = suppressed

Number

8 1 2-3

4

ISE DCC WCC BSR

MJO Phase

Large-Scale 1000-750 hPa Shear

ms-1

Frequency (%) ISE DCC WCC BSR

Number

Shading = shear

magnitude

Strong Low-Level Shear Favors Development with Locally Stronger

Surface Convergence

Houze et al. 1989

Convective CoreStratiform Region

Strong Low-Level Shear Favors Development with Locally Stronger

Surface Convergence

CC

Houze et al. 1989

MJO Phase

Large-Scale 750-200 hPa Shear

ms-1

Frequency (%) ISE DCC WCC BSR

Shading = shear

magnitude

Very Strong Upper-Level Shear Separates Stratiform from

Convective Moisture

Houze et al. 1989

Houze et al. 1989

Very Strong Upper-Level Shear Separates Stratiform from

Convective Moisture

Houze et al. 1989

Very Strong Upper-Level Shear Separates Stratiform from

Convective Moisture

Precipitating Cloud Population and Large-Scale Atmospheric Conditions

Pre Active Active Post Active

Phase 1 2 3 4

DCC Peak Decrease

WCC, BSR Increase Peak Decrease

Mid-Level Relative

Humidity

Sharp Increase

Slower Increase Peak Decrease

Low-Level Shear Increase Peak

Upper-Level Shear Increase Peak

Southeast West Pacific (SEWP) Analysis

MJO in the SEWP1

2

3

4

5

6

7

8

Transition to Active

Active

Transition to Suppressed

Suppressed

Isolated Shallow Echoes

%

10N

10S

140E

0

170E

MJO Phase

Frequency (%)20 samples (blue), average (black), and 99% confidence interval (red)

Deep Convective Cores

%MJO Phase

Frequency20 samples (blue), average (black), and 99% confidence interval (red)

Broad Stratiform Regions

%

MJO Phase

Frequency (%)20 samples (blue), average (black), and 99% confidence interval (red)

MJO Precipitating Cloud Population• All cloud types significantly vary

• ISE suppressed, 3 phases before active • BSR one phase before DCC and WCC

• Areal variability - BSR dominate• Number variability

• ISE dominate

• DCC > WCC > BSRArea Number Number

MJO Phase

x10^4ISE DCCWCC BSR

%

MJO Phase

Large-Scale Relative Humidity

MJO Phase

Frequency (%)

Relative Humidity (%)

Number

Solid lines = active, dashed = suppressed

4-56-7

ISE DCC WCC BSR

Large-Scale 1000-750 hPa ShearFrequency (%)

ms-1

MJO Phase

ISE DCC WCC BSR

Number

Shading = shear

magnitude

Large-Scale 750-200 hPa Shear

ms-1

MJO Phase

Frequency (%)

ISE DCC WCC BSR

Shading = shear

magnitude

Precipitating Cloud Population and Large-Scale Atmospheric Conditions

Pre Active Active Post Active

Phases 5 6 7 8DCC, WCC Increase Peak Decrease

BSR Increase Peak DecreaseMid-Level

Relative Humidity

Increase Peak Decrease

Low-Level Shear Increase Peak DecreaseUpper-Level

Shear Increase Peak Decrease

Conclusions Precipitating Cloud Population

• Precipitating cloud population varies significantly• Areal variability – BSR dominate• Number variability

• ISE dominate• DCC & WCC > BSR

Central Indian Ocean Southeast West Pacific Ocean

ISE Suppressed, after active

Suppressed, before active

BSR Active Active

DCC and WCC Active, with BSR Active, one phase after BSR

Conclusions:Precipitating Cloud Population and

Large-Scale Atmosphere

DCC WCC BSR

Mid-Level Relative Humidity

Relatively Moist Moist Moist

Low-Level Shear Relatively Strong Strong Strong

Upper-Level Shear -- -- Moderate

• RH leads then positive feedback with the deep convection• Strong low-level shear -> strong surface convergence• Very strong upper-level shear -> stratiform torn from convective

source

Future Work

• Kinematics and microphysics • 11 rain events, Zuluaga and Houze (2013)• Compare kinematics to TOGA COARE • Expand with microphysical data• Relate storm structure to large-scale

• Modeling???

(Kingsmill and Houze 1999a)

Acknowledgements• Bob Houze

• Committee

• Rob Wood and Mike Wallace

• Beth Tully

• Houze group

• 626 Officemates

• Grads 2010

• Family

• Funding• DOE DE-SC0001164 / ER-64752 and DE-SC0008452• DYNAMO – NSF AGS-1059611• PMM-NASA Grant NNX10AH70.