mesoscale convective systems in the initiation of the mjo
DESCRIPTION
Mesoscale Convective Systems in the Initiation of the MJO. Jian Yuan and Robert A. Houze University of Washington. CloudSat/CALIPSO Science Team Meeting Montreal, Quebec, Canada, 16 June 2011. The Madden-Julian Oscillation (MJO): Play important roles in weather and climate - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/1.jpg)
Mesoscale Convective Systems in the Initiation of the MJO
Jian Yuan and Robert A. HouzeUniversity of Washington
CloudSat/CALIPSO Science Team Meeting Montreal, Quebec, Canada, 16 June 2011
![Page 2: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/2.jpg)
The Madden-Julian Oscillation (MJO):
• Play important roles in weather and climate
• Current prediction skill, especially for the initial phase of MJO is very limited
• Cumulus parameterizations in GCMs is the primary limiting factor in MJO simulation and prediction.
(Zhang et al. 2010, DYNAMO)
(Courtesy of US CLIVAR MJO Working Group)
![Page 3: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/3.jpg)
MJO initiation processes
Feedbacks between:
•Clouds•Radiative heating•Convection•Precipitation •Ocean
are a key to understanding the MJO.
Fundamental processes related to MCSs that are crucial to understand MJO:
•the diabatic heating structure•convective sensitivity to environmental moisture•cloud microphysics•convective organization
Courtesy of Zhang et al. 2009, DYNAMO After Stephens et al. 2004, “Humidistat Feedback”
![Page 4: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/4.jpg)
MCSs including both raining and anvil components are identified using A-Train
instruments
Yuan and Houze 2010
![Page 5: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/5.jpg)
MODIS TB11 + AMSR-E (Yuan and Houze 2010)
combined to find“cold centers” & “raining areas”
Use 260 K threshold
Locate 1st closed contour
Use 1 mm/h threshold for rain rate
Associate pixels with nearest cold center
Use 6 mm/h threshold for heavy rain
![Page 6: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/6.jpg)
MCS Criteria (Yuan and Houze, 2010)
Systems whose largest raining cores have
• Area > 2000 km2
• Min TB11 ≤ 220 K
Must have one dominant core
• with intense cells, and• accounting for >70% rain area56% all tropical rain
![Page 7: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/7.jpg)
MCSs are further divided to two groups :
1.Separated (40 % rain fall)
1.Connected (>=3 MCSs share the same rain feature, 16% rain fall)• Separated MCS: Frequently found over all
convective zones, especially continents
• Connected MCS: more organized convection, primarily found over warm ocean area
![Page 8: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/8.jpg)
MODIS/AMSR-E/CloudSat
identifies MCSs obtains the global distribution of MCSs
investigates variability of MCSs in MJO
(EIO:-15-15oN;75-100oE; Composite of 8 phases; Wheeler and Hendon 2004)
![Page 9: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/9.jpg)
More Connected MCSs observed in MJO
active phases
OLR
![Page 10: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/10.jpg)
Deeper MCSs observed in pre-onset, initial and active phases
![Page 11: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/11.jpg)
Low level Θe likely determines the Tb_min
(“hot tower” hypothesis)
Phase 1-3
Phase 5-7
Climatology of EIO:
•T150 hp ≈ 205 K
•Θe150 hp≈ 352.6 K
![Page 12: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/12.jpg)
Moisture effects need to be better understood
Deeper MCSs
Deeper MCSs
Less MCSs; less
organized
More MCSs; more
organized
![Page 13: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/13.jpg)
Summary and Conclusions
A-Train instruments make it possible to identify MCSs (raining + anvil components) globally
MJO pre-onset phase active phases over EIO:
Deeper MCSs & Warmer low level Θe (both)
Less More MCSs
Relatively Less More organized MCSs
Drier Moister middle troposphere
![Page 14: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/14.jpg)
End
![Page 15: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/15.jpg)
MJO activities viewed in OLR
![Page 16: Mesoscale Convective Systems in the Initiation of the MJO](https://reader035.vdocuments.us/reader035/viewer/2022062809/568157c9550346895dc553e2/html5/thumbnails/16.jpg)
MCSs Over the Whole Tropics: oceanic conditions favor larger systems
Smallest 25% (<12,000 km2)
Largest 25% (>40,000 km2)
“Superclusters”