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Yoshi-Yuki Hayashi Yukiko Yamada Yoshiyuki Takahashi Masaki Ishiwatari Mayumi Yoshioka

On the varieties of forced and spontaneously generated tropical precipitation patterns: some expectations and results. Yoshi-Yuki Hayashi Yukiko Yamada Yoshiyuki Takahashi Masaki Ishiwatari Mayumi Yoshioka Wataru Ohfuchi Takeaki Sampe Kensuke Nakajima

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Yoshi-Yuki Hayashi Yukiko Yamada Yoshiyuki Takahashi Masaki Ishiwatari Mayumi Yoshioka

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  1. On the varieties offorced and spontaneously generatedtropical precipitation patterns:some expectations and results Yoshi-Yuki Hayashi Yukiko Yamada Yoshiyuki Takahashi Masaki Ishiwatari Mayumi Yoshioka Wataru Ohfuchi Takeaki Sampe Kensuke Nakajima 1)Hokkaido University, 2)University of Tokyo, 3)Kyushu Universtiy, 4)ESC/JAMSTEC shosuke@gfd-dennou.org 2005-04-20 Reading, U.K.

  2. Contents • equatorial disturbances • From Hayashi & Sumi 1986 + Numaguti & Hayashi 1991 • Classical image: wave-CISK, WISHE • eastward vs. westward • advection or wave • planeary scale modulation? • steady response to SST anomaly • Hosaka et al 1998 vs. Hoskins & Neele 2000

  3. equatorial disturbances

  4. Hayashi and Sumi 1986Numaguti and Hayashi 1991a,b 20 years ago … • aqua planet condition • the first global NWP model of Japan Met. Agency • run at the Univ. of Tokyo • T42L12 • cumulus parameterization • Kuo (Hayashi & Sumi 1986) • Kuo and Adjustment (Numaguti & Hayashi 1991a, b) Hayashi & Sumi 1986 JMSJ64 451

  5. Hayashi and Sumi 1986 • super (cloud) clusters: eastward moving feature with a scale of a few grids • wave number one modulation (30 day oscillation): inhomogeneous distribution of super clusters • double ITCZ Hayashi & Sumi 1986 JMSJ64 451

  6. super cloud clusters: spurious or real • since their scale is at the edge of the model resolution, • they were, at the beginning, regarded as computational noise. • Nakazawa 1986, equatorial OLR x-t diagram • with the time resolution higher than those plotted before, • gives some reality; many eastward features are identified • within one active ISV phase Nakazawa 1986 JMSJ64 777

  7. super cloud clusters in the model: Kelvin wave-CISK • Kuo scheme is regarded to be wave-CISK friendly • Composite structure resembles those expected for Kelvin wave-CISK Numaguti & Hayashi 1991 JMSJ69 541

  8. no wind feedback (zonal mean ) wave number one modulation (30 day oscillation): WISHE, frictional convergence? • An experiment without surface wind feedback (longitudinally uniform evaporation) • show little evidence of wave number one modulation Kuo Adjustment Numaguti & Hayashi 1991 JMSJ69 563 with wind feedback • However, Lee et al (2003) argues that frictional convergence is important.

  9. A simple way of thinking from old days: near the grid scale • equatorial wave-CISK • with an asymmetric feedback • where heating occurs only when • low level vertical wind is positive • tends to present • only Kelvin coherent (non dispersive) • wave packet. • (Lau and Peng 1987) equatorial wave (no feedback) positive only CISK feedback Kelvin wave with single upward region linear CISK feedback Kelvin and westward gravity wave packet http://www.gfd-dennou.org/arch/ape/wavecisk

  10. A simple way of thinking from old days: near the grid scale • Hence, super cloud clusters may be regarded as a realization of • Kelvin wave-CISK. • Size of super cloud clusters is larger than covering several cloud • clusters. • according to the prediction of growth rate of wave-CISK theory, • it must be the smallest size in the range where dynamics of • convective cloud system (mesoscale dynamics) does not interfare. • Because of the limitation of model resolution and representation of • moist process, grid scale convection in a model can represent as • super cloud clusters (Kelvin wave-CISK) propagating eastward • convective system advected westward mainly by the background • wind (cloud clusters) • A model may represent both or either of them. • A higher resolution model may represent envelope eastward • super cloud cluster and internal cloud clusters.

  11. AGU for APE cumulus comparison (T39L48) eml ias kuo kuo-sc Adjust non

  12. Takayabu (1998), Wheeler and Kiladis (1999) • signals corresponding to westward gravity waves are identified. • So do some models

  13. AGU for APE cumulus comparison (T39L48) eml ias kuo kuo-sc Adjust non

  14. AGU for APE cumulus comparison (T39L48) Qobs eml ias kuo kuo-sc Adjust non

  15. AGU for APE cumulus comparison (T39L48) Qobs • Three types of grid scale precipitation • basically westward propagating + some eastward • basically eastward propagating modulated by westward moving envelop • both eastward and westward convective areas are similar • appearance

  16. AGU for APE cumulus comparison (T39L48) Qobs eml ias kuo kuo-sc Adjust non

  17. model comparison AGUforAPE(eml) GSFC CSIRO K1JAPAN LASG MGO UKMOn48 NCAR UKMOn96

  18. model comparison AGUforAPE(eml) GSFC CSIRO K1JAPAN LASG MGO UKMOn48 NCAR UKMOn96

  19. Heating profile (CISKy condition) and waves by a simple AGCM5.3 model (Kuo) • westward gravity waves seem to be also coupled • with convection. radiative cooling weighted in the lower layer radiative cooling weighted in the upper layer http://www.gfd-dennou.org/arch/ape/agcm5/mradl/kuo-mradlA-xteq.html

  20. Heating profile (CISKy condition) and waves by a simple AGCM5.3 model (adjustment) • westward gravity waves also coupled radiative cooling weighted in the lower layer radiative cooling weighted in the upper layer http://www.gfd-dennou.org/arch/ape/agcm5/mradl/mradlA-xteq.html

  21. Planetary scale modulation • Eastward propagating low frequency large scale modulation does not • seem to appear very frequently • Super cloud clusters vs. planetary scale modulation

  22. AGU for APE (T159L48, none) flat Large scale modulation

  23. Planetary scale modulation • Super cloud clusters vs. planetary scale modulation. • How do we recognize them? These may be considered as higher resolution version of super clusters, wave-CISK like features, rather than a planetary scale modulation.

  24. Planetary scale modulation • How about those? FRCGC K1JAPAN AGUforAPE T159 non flat • This must be different from super cloud clusters

  25. steady response to SST anomaly

  26. Hosaka el al 1998 JMSJ • precipitation increase to the east of SST anomaly • Neal & Hoskins 2001 ASL(3keq) • precipitation decrease both to the east and west

  27. Set up of Hosaka et al. 1998 • AGCM5.3 GFD Dennou Club • by Numaguti • from JMA NWP model • prototype of • CCSR/NIES model • SIMPLE • simple radaitive process • three bands for • dry atmosphere • one band for • water vaper • no cloud, no rain • T42L16 • 4K (3.6K on the grid) SST • anomaly • Hosaka et al 1998 JMSJ 76 289

  28. surface pressure response of Hosaka et al. 1998 • To the east • wide extension of low pressure anomaly • associated with Kelvin wave like response • To the west • narrow extension of low pressure anomaly • associated with Rossby wave like response, and • high pressure anomaly Hosaka et al 1998 JMSJ 76 289

  29. Initial development of SST response exemplified by 128 ensemble mean • To the east • Precipitation decreases as (moist) downwelling Kelvin wave front arrives, and then • precipitation increases because of Ekman convergence toward the equatorial • low pressure associated with the Kelvin wave. • To the west • Precipitation continues to decrease after the arrival of • Rossby wave, since Ekman flow is diverging near the equator. • Toyoda et al 2000 Nagare Multi Mdeia • http://www.nagare.or.jp/mm/99/toyoda/ • Nakajima et al 2004 JMSJ 82 1483 precipitation pressure

  30. precipitation response to the east of SST anomaly • Precipitation to the east of the SST anomaly increases because of • the Ekman convergence associated with the low pressure anomaly • caused by the warm Kelvin wave response extending from • the convection center (SST anomaly region). • Hence, if the equatorial low pressure anomaly is week compared • to the off-equatorial latitudes, • precipitation may not increase. • Equatorial surface pressure may not be low enough when • condensation heating is top heavy so that • second baroclinic mode is more intense. • Realistic models which include sophisticated moist processes • and radiation feedbacks cause top heavy profile • compared to simple AGCM5.3.

  31. model comparison: precipitation anomaly (3Keq) GSFC AGUforAPE K1Japan LASG NCAR UKMO96

  32. model comparison: surface pressure anomaly (3Keq) GSFC AGUforAPE LASG K1Japan NCAR UKMO96

  33. AGU for APE cumulus comparison (T39L48) 3Keq eml ias kuo kuo-sc Adjust non

  34. AGU for APE cumulus comparison (T39L48) flat3Keq eml ias kuo kuo-sc Adjust non

  35. AGCM5.3 (simple model, T42L16) 3Keq flat3Keq Qobs3Keq H1998

  36. AGCM5.3 (simple model, T42L16) 3Keq flat3Keq Qobs3Keq H1998

  37. AGU for APE zonal mean precipitation (T39L48) eml ias kuo kuo-sc Adjust non

  38. model comparison: zonal mean precipitation GSFC AGUforAPE LASG K1Japan NCAR UKMO96

  39. Some confessions • Aqua planet is not easy to understand. • It seems that I do not dislike wave-CISK as a crude theory of • instability caused by wave-wave interaction coupled by • condensation heating. • in other word, I do not have any good simple device to describe • what is going on in the model. • Hayashi and Sumi (1986) is not very robust, rather fragile. • However, according to late Numaguti, you can tune most of the • parameterizations to reproduce eastward coherent motion of • grid scale activities. • But its tuning does not seem to be easy. • Integration period of those old GCM runs of Hayashi & Sumi (1986) • or Numaguti & Hayashi (1991) is too short to confirm robustness of • planetary scale modulatio. Figures of AGUforAPE are available from http://www.gfd-dennou.org/arch/ape/

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