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 1)Hokkaido University, 2)University of Tokyo, 3)Kyushu Universtiy, 4)ESC/JAMSTEC Reading, U.K.

Contents equatorial disturbances –From Hayashi & Sumi 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

equatorial disturbances

Hayashi and Sumi 1986 Numaguti and Hayashi 1991a,b 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 JMSJ years ago …

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 and Sumi 1986 Hayashi & Sumi 1986 JMSJ

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 JMSJ

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

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

equatorial wave (no feedback) 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) linear CISK feedback positive only CISK feedback Kelvin and westward gravity wave packet Kelvin wave with single upward region 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. A simple way of thinking from old days: near the grid scale

AGU for APE cumulus comparison (T39L48) emlias kuo-sc kuo Adjustnon

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

AGU for APE cumulus comparison (T39L48) emlias kuo-sc kuo Adjustnon

AGU for APE cumulus comparison (T39L48) Qobs emlias kuo-sc kuo Adjustnon

Three types of grid scale precipitation 1. basically westward propagating + some eastward 2. basically eastward propagating modulated by westward moving envelop 3.both eastward and westward convective areas are similar appearance AGU for APE cumulus comparison (T39L48) Qobs

emlias kuo-sc kuo Adjustnon

AGUforAPE(eml) CSIRO GSFC K1JAPANLASGMGO NCAR UKMOn48 UKMOn96 model comparison

AGUforAPE(eml) CSIRO GSFC K1JAPANLASGMGO NCAR UKMOn48 UKMOn96 model comparison

radiative cooling weighted in the upper layer radiative cooling weighted in the lower layer westward gravity waves seem to be also coupled with convection. Heating profile (CISKy condition) and waves by a simple AGCM5.3 model (Kuo)

radiative cooling weighted in the upper layer radiative cooling weighted in the lower layer westward gravity waves also coupled Heating profile (CISKy condition) and waves by a simple AGCM5.3 model (adjustment)

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

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

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.

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

steady response to SST anomaly

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

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 Set up of Hosaka et al. 1998

surface pressure response of Hosaka et al 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

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. pressure precipitation Initial development of SST response exemplified by 128 ensemble mean Toyoda et al 2000 Nagare Multi Mdeia Nakajima et al 2004 JMSJ

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.

GSFC AGUforAPE K1JapanLASG NCAR UKMO96 model comparison: precipitation anomaly (3Keq)

AGUforAPE GSFC K1Japan LASG NCARUKMO96 model comparison: surface pressure anomaly (3Keq)

AGU for APE cumulus comparison (T39L48) 3Keq emlias kuo-sc kuo Adjustnon

AGU for APE cumulus comparison (T39L48) flat3Keq emlias kuo-sc kuo Adjustnon

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

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

AGU for APE zonal mean precipitation (T39L48) emlias kuo-sc kuo Adjustnon

AGUforAPE GSFC K1Japan LASG NCARUKMO96 model comparison: zonal mean precipitation

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