Western Pacific Cloud Population as a Function of the Phase of the MJO

1. Western Pacific Cloud Population as a Function of the Phase of the MJO Hannah Barnes Robert A. Houze Jr. First Year Presentation University of Washington September 21, 2011

2. The Convectively Coupled Madden – Julian Oscillation (MJO) West East z Drying Moistening Suppressed Active Suppressed (Zhang, 2005)

3. Propagation of the MJO Convective Initiation: Indian Ocean (60E) Convective Propagation: Maritime Continent, Western Pacific 5 m/s Convective Dissipation: Dateline (180E) Upper tropospheric / dry mode: Circumnavigates ~30 m/s Period: 30 – 100 days (Zhang, 2005)

4. Significance of the MJO • Intraseasonal tropical variability • (Weickmann et al., 1985), (Lau and Chan, 1985) • Australian, South Asian, Indian Monsoon (Zhang, 2005) • Hurricane genesis in Pacific, Caribbean (Zhang, 2005) • ENSO • (Zhang, 2005) • United States primarily during Winter • (Zhou, 2011) • OND Precipitation varies west of Cascades • (Bond and Vecchi, 2003)

5. Suppressed Phases of the MJO 1 2 • Wheeler and Hendon, 2004 • EOF analysis • OLR, 850 and 200 hPa zonal winds • Real-Time Multivariate MJO Series 1 & 2 • (RMM1 & RMM2) • Large scale eastward propagation • Divided into 8 phases 3 4 Active 5 6 7 Suppressed 8

6. Extreme stratiform and convective variation with phase of the MJO • 10S – 10N, 140E – 170E • Oct – Feb: 1998 – 2011

7. The TRMM Satellite Ku-band Radar Low altitude, low inclination orbit

8. TRMM Satellite Instrumentation λ= 2 cm Important! PR measures 3D structure of radar echoes Kummerow et al, 1998

9. Oldconvection Vigorousconvection 100 km Subdivision of tropical precipitation into convective and stratiform components (Houze, 1997)

10. Vertical structure of a mesoscale system Storm motion (Houze et al. 1989)

11. Identify each contiguous 3D echo objectseen by TRMM PR Convective component Stratiform component Extreme characteristic Contiguous 3D volume ofconvective echo > 30 dBZ Extreme characteristic Contiguous stratiform echowith horizontal area > 50 000 km2 “Broad stratiform region” Top height > 8km “Deep convective core” Horizontal area >800 km2 “Wide convective core”

12. Large Precipitation Regions Vary More with the MJO than Small Stratiform rain fraction variance 1.7x greater (Morita et al., 2006) 30 dBZ height similar in active and suppressed stages (DeMott and Rutledge, 1998a) Also (Mapes and Houze, 1993) (Yuter and Houze, 1998) Stratiform Convective Figure 1. East-West structure of the rainfall rate anomaly of convective rain (broken: left ordinate) and stratiform rain (dotted: left ordinate), and OLR anomaly (solid: right ordinate, upside down). Abscissa is relative longitude. (Morita et al., 2006)

13. Deep Convective Cores--Small Variability 30 dBZ 8 km Phase 3 Phase 1 Phase 5 Phase 7

14. Deep Convective Cores--Small Variability Land Ocean Variance < 0.04 %

15. Broad Stratiform Regions—Large variation with phase of MJO 50,000 sqkm Phase 2 Phase 4 Phase 6 Phase 8

16. Broad Stratiform Percentage maximum in phases 5, 6 minimum in phases 2, 3 Land Ocean Variance < 1% Variance < 0.1 %

17. Variability Dominated by Broad Stratiform Regions in Western Pacific Ocean Land Mesoscale systems vary more than other convection

18. Lag Correlation of CloudRadar & Lidar Data Non-precipitating, shallow, and congestus theorized to precondition (Blade and Hartmann, 2003), (Benedict and Randall, 2007), (Lu and Wu, 2010), (Stephens and Wood, 2007) (Del Genio et al., 2011 Submitted)

19. Lower Tropospheric RH Constant, Convergence Maximum Phase 5, 6 850 hPa Phase 2 Phase 4 Phase 8 Phase 6

20. Mid - Upper Tropospheric RH Varies with MJO, Reduced Convergence 500 hPa Phase 2 Phase 4 Phase 8 Phase 6

21. Conclusions • Deep and wide convective cores exhibit small variability with phase of MJO • Broad stratiform regions maximum during active and minimum during suppressed phases •  Well organized, late stage mesoscale convective systems • RH modulated in mid-upper troposphere • Lower troposphere RH uniformly moist

23. Five radars on a tiny island Addu Atoll

24. Radar Supersite Approach Will document many aspects of the convective population * HUMIDITY DOPPLER Air motions DUAL WAVELENGTH Water vapor CM-WAVELENGTH Precipitation MM-WAVELENGTH Non-precipitating Cumulus MM-WAVELENGTH Anvil cloud POLARIMETRY Microphysics

25. Acknowledgements Professor Robert A Houze Jr. Stacy Brodzik Mesoscale Group Grads 10

26. Conclusions • Deep and wide convective cores exhibit small variability with phase of MJO • Broad stratiform regions maximum during active and minimum during suppressed phases •  Well organized, late stage mesoscale convective systems • RH modulated in mid-upper troposphere • Lower troposphere RH uniformly moist

27. Wide Convective Phase 2 Phase 4 800 sqkm 30 dBZ Phase 6 Phase 8

28. Wide Convective Variability Insignificant with MJO Phase Land Ocean Variance < 0.04 %

29. Tropical Convective Clouds • DEEP CONVECTION • Capped by tropopause • Least frequent • Most rainfall • Related to large-scale circulation • CUMULUS CONGESTUS • Capped by 0C • Most frequent • Only in tropics • Evaporation and detrainment moistens lower and mid-troposphere • SHALLOW CUMULUS • Capped by trade inversion • Related to local thermodynamics • Evaporation and detrainment moistens lower troposphere Johnson 1999

30. TRMM Precipitation Radar • Tropical Rainfall Measuring Mission • First weather radar in space • 1998 – present ; 35S to 35N • 3D climatology of tropical convection from • Logistics: • Ka band (2.17 cm, 18.5 GHz) • Active phased array • 247 km swath width • 5 km horizontal resolution • 0.25 km vertical resolution • Limitations: • Low sensitivity (~17 dBZ, 0.4 mm/hr) • Attenuated in heavy precipitation • Low resolution, misses small convection Kumerrow et al, 1998 • Version 6 products used: • 2A25 – Gridded attenuated corrected reflectivity (Iguchi et al., 2000a,b) • 2A23 – Convective / stratiform classification (Awaka et al, 1997; Awaka et al., 2009) • Version 7 recently released (increase convective by 7%)