2012/9/19

熱帯積雲対流に及ぼす大気大規模循環の効果
熱帯降雨観測衛星および気候モデルデータ
解析研究から
東京大学大気海洋研究所
高薮 縁
協力： 廣田渚郎、重尚一、W.‐K. Tao
渡部雅弘、木本昌秀

09/19/2012神戸大セミナー

Effects of the large‐scale circulation on
tropical cumulus convection
Yukari N. Takayabu
Atmosphere Ocean Research Institute (AORI)
the Univ. Tokyo
Collaborators:
Nagio Hirota (U. Tokyo)
Shoichi Shige (Kyoto Univ)
Wei‐Kuo Tao (NASA/GSFC)
Masahiro Watanabe (U. Tokyo)
Masahide Kimoto(U. Tokyo)
09/19/2012神戸大セミナー

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目次• 自由対流圏の湿度依存性に関する観測研究からの示唆• TRMM衛星観測に見られる熱帯降雨の２レ
ジーム：deepとshallow(ここではcongestus)• CMIP3, CMIP5 気候モデルにおける対流パラメタリゼーションの湿度依存性‐‐double ITCZ問題との関連• CRM研究からの示唆
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Tropical clouds are under the influences of SST andlarge‐scale circulation
Warm SST destabilize the tropicalatmosphere  cumulus
convection starts to stabilize

TRMM

CbConvective
warm rainhigh SST

Large-scale subsidence generates
trade inversion and suppresses
the deep convection (historicalview) Recent studies (e.g. Bretherton
et al. 2004) indicate theimportance of the freeStratocumulus
tropospheric humidity for deep& cumulus
convection
low SST

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TOGA-COARE revealed the tri-modality of the tropical convection

Abundance of cumulus
congestus

Johnson et al. 1999
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Effects of subsidence observed with the MJO

TBB

Cloud Top Temperaturein TOGA‐COARE period

Three‐steps‐wise development ofconvections is observed inassociation with MJO.
Relative Humidity

Pressure

In the shallow‐convection stage,
mid‐troposphere is very dry,indicating strong subsidence as apart of the MJO structure.

Kikuchi and Takayabu (2004, GRL)

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Time3

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Similarity of lifecycles in various organized convection systems

Mapes et al. (2006, DAO)

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Lag‐correlations btwn WV mixing ratio and GMS IR TBB
865 sondes launced over ocean from R/V Mirai, R/V Kaiyo, and R/V Natsushima

Takayabu, Yokomori et al. (2006, JMSJ)
Significance of mid‐level humidity as a precursor of deep convection is suggested,consistent with Brown and Zhang (1997), Sherwood (1999), Bretherton et al. (2004), etc.
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Brown and Zhang (1997)

Numaguti et al. (1995) and Yoneyama et al. (1995) suggested the mid‐level dry
intrusion associated with an MJO significantly suppressed the deep convection.
Consistently, in the drought period (Nov.12‐21) of TOGA‐COARE IOP, significant
difference in RH is found in the mid‐to‐upper troposphere above 700hPa. (Brownand Zhang, 1997)
09/19/2012神戸大セミナー

Bretherton et al. 2004

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Re‐boost effect on the effective buoyancy
with latent heating of freezing (Zipser, 2003)

09/19/2012神戸大セミナー• Discreteness of tropical convection• Rareness of undiluted convection

Takayabu, Y. N., S. Shige, W.‐K. Tao, and N. Hirota, 2010, J. Clim.

SHALLOW AND DEEP LATENT HEATING MODES OVER
TROPICAL OCEANS OBSERVED WITH TRMM PR SLH DATA

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Tropical Rainfall Measuring Mission
TRMM PR Single Orbit Rain Observation
8 Dec 1997 16:41-18:13

presented by NASDA (JAXA)

Swath width: ~220km Orbits: ~16 times/day

TRMM: Tropical Rainfall Measuring Mission
TMI
TRMM Microwave
Imager(Precipitation, Sfcwnd,SST, Precipitable water)
10,19,21,37,85 GHz

LISLighteningImaging Sensor

VIRS

CERES

Visible Infrared Scanner(Clouds)
0.63, 1.6, 3.75,
10.8, 12.0 μｍ

Clouds and Earth
Radiation Energy System(Broadband Radiation)
0.3-5, 8-12,0.3-50 μｍ

PR

Precipitation Radar(Precipitation Profiles)
13.8GHz7

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TRMM降雨観測

PR Swath width: 215km (245km) Orbits: ~16 times/day

TRMM PR による3次元降雨観測
Tropical Cyclone
PAM
8 Dec 1997

Horizontal Cross Section of Rain at 2.0km

3-D Rain Structure

JAXA EORC 提供

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降雨の日変化

降雨特性：降雨量/発雷比

Takayabu, 2006

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Apparent Heat Source (Yanai et al. 1973)
Q1 sDs s  v  s  
Dt tp QR  L(c  e)    s' v'  s'  'pwhere s  CpT  gz dry static energy: grid mean, ' : deviation from the grid mean

• 3D Q1‐QR data from the SLH database are used:generated in TRMM2A25 original resolution and gridded
into monthly, 0.5degx0.5deg: L3LH, Dec.1997‐Nov.2007
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Shige et al. (2004)

http://www.eorc.jaxa.jp/TRMM/lh/index.html

Data: TRMM Spectral Latent Heating (SLH)
Shige et al. 2004, JAMC

TRMM PR2A25 orbital data
Rain TypePrecip. Top Height
Melt-Lvl Precip.
Sfc Precip.

Rain-LH tables

GCEM

total

Estimate LH Data
StratConv

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TRMM SLH Q1‐QR

ALL 98‐07 20N‐20S

Altitudes (km)Ocean

LandTotal~8km

Organized

Stratiform~5km~2km：
warm rain
RTH~4km
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K/dayConvective(Takayabu et al. 2010)

Warm convective rainor cumulus congestus

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10‐year mean Q1‐QR JJA 98‐07
Deep Organized Systems

7.5km

Cumulus Congestus

2.0km

09/19/2012神戸大セミナー(Takayabu et al. 2010)

10‐year mean Q1‐QR & SST JJA 98‐07
Deep Organized Systems

7.5km

25℃

Cumulus Congestus

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2.0km(Takayabu et al. 2010)12

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10‐year mean Q1‐QR & ω500 JJA 98‐07
Deep Organized Systems

7.5km

Cumulus Congestus

2.0km

09/19/2012神戸大セミナー(Takayabu et al. 2010)

Cond‐Mean Q1‐QR & RH vs 500hPa 30N30S 9804
Q1‐QR

RH
22-23℃

24-25℃

26-27℃

28-29℃

In order to separate the effects of large‐scale circulation from those of SST, plots are
separated in terms of SST. It was shown that similar significant dryness in the mid‐
09/19/2012神戸大セミナー
to‐lower
troposphere is found in the subsidence region irrespective of the SST.

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TRMM SLH Q1‐QR, JRA25 winds, RH
SON98‐05 10S

09/19/2012神戸大セミナー(Takayabu et al. 2010, modified)Unconditional mean Q1‐QR vs. SST 97‐05 30N‐30S
7.5km heating
Deep rain

JJA

JJA

88

Q1-QR (K/day)

Q1-QR (K/day)

2.0km heating
cumulus congestus
64264
200
1618 20 22 24 26 28 30 32SST1618 20 22 24 26 28 30 32

SST

While congestus responds linearly to SST, which means obedient tothe low‐level instability, deep rain is controlled by another factor.

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From the TRMM SLH Analysis• Distinct two regimes of convective heating with
TRMM‐PR based Q1‐QR; a cumulus congestus
rain with a peak at ~2km, and with a peak fordeep organized rain at ~8km.
• Under large‐scale subsidence, cumulus
congestus rain dominates over ocean, but notover land.
• Congestus rain responds linearly to SST, while
deep organized convection is effectively
suppressed by large‐scale subsidence, probably
through the entrainment of free tropospheric
dry air.
09/19/2012神戸大セミナー

Hirota, N., Y. N. Takayabu, M. Watanabe, and M. Kimoto, 2011
J. Climate

PRECIPITATION REPRODUCIBILITY OVER TROPICALOCEANS AND ITS RELATIONSHIP TO THE DOUBLEITCZ PROBLEM IN CMIP3 AND MIROC5* CLIMATE
MODELS*MIROC5: U.TOKYO/JAMSTEC/NIES NEW MODEL FOR CMIP5

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Double ITCZ in climate models
Precipitation (color), SST (contour) [SON]TRMM

5 CMIP3 LS models• Systematic precipitation bias over the southeastern Pacifc(Mechoso et al. 1995; Szoeke and Xie 2008)• Double ITCZ appears even in AGCMs(Zhang et al. 2007; Chikira, 2010)• Mitigated by modification of convective parameterization
09/19/2012神戸大セミナー(Song and Zhang 2009, Chikira 2010)(Hirota et al., 2011)

Effects of SST and subsidence
Heating (color; TRMM SLH) stratified against ω500 (abscissa; JRA)
ascending⇔subsidence(Takayabu et al. 2010)
We have seen subsidence regions had very dry layer in the middle trop. (~600 hPa)
→ Entrainment of dry air reduces buoyancy of convection→ suppression of deep convection
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DOUBLE ITCZ IN CMIP3 MODELS

09/19/2012神戸大セミナー

熱帯海洋上の降雨分布とCMIP3, CMIP5モデルのダブルITCZ問題
 深い対流のSSTと環境場の湿度への感度
Precipitation distributions over the tropicaloceans and the double ITCZ problem in CMIP3and MIROC5 models are investigated, in termsof sensitivity of deep convection to SST andenvironmental humidity.

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TRMM

CMIP3 SST (contour) and Precipitation (color)

09/19/2012神戸大セミナー[mm/day](Hirota et al., 2011)

Observation

TRMM PR 2A25

CMIP3BCCR

GISS_E_R

CCCMA*IAP

CCCMA_t63*

INGV_ECHAM4

CNRM

INMCM3*CSIRO_0

MIROC_H

CSIRO_5

MIROC_M

GFDL_0MIUB*

GFDL_1

MPI_ECHAM5

GISS_AOMMRI*GISS_E_H(*flux adjustment)

For CMIP5

MIROC5

Precipitation distributions in CMIP3 models and new MIROC5 areevaluated against the TRMM Precipitation Radar data

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Taylor’s score for precip distribtion
for 30N‐30S

Double ITCZ ~ Taylor(2001)’s score for tropical precip.

Double ITCZ index

Among CMIP3 models, Taylor(2001)’s score for tropical (30N‐30S) annualprecipitation and the double ITCZ index have a significant negative correlation.
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Modified from Hirota et al. 2011 JC

CMIP3 High and Low Performance Models
in tropical precip. distribution(30N‐30S 0‐360E)
5 High Performance Models

High performance models
in terms of precipitation
distribution also behave
well with ITCZ structure,
for CMIP3 models.

5 Low Performance Models

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Diabatic Heating (Q1)sorted with RH600hPa
5 High Performance Models

CMIP3Convection in high performancemodels is more sensitive to the
mid‐to‐lower tropospheric relativehumidity. So that deep convection
is effectively suppressed when the(Hirota et al., 2011)
RH600 is low.

5 Low Performance Models

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dry←RH600[%]→humid

High PM – Low PM

dry←RH600[%]→humid

CMIP5 CASE

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Taylor’s score for tropical precip.: CMIP3 vs CMIP5(Taylor, 2001)(Hirota et al., 2012)

MIROC5Ref: TRMM

CMIP5

CMIP3

Average = 0.63

Average = 0.59

DI09/19/2012神戸大セミナー←Corr -0.8→ Taylor Score

DI ←Corr -0.2→ Taylor Score

CMIP5 for ITCZ distribution(Hirota et al., 2012)

No Double ITCZ

5 No Double ITCZ models

Double ITCZ

5 Double ITCZ models

CMIP5 models without double ITCZ problem
also tend to be sensitive to the mid‐to‐lower
tropospheric relative humidity, suggesting
the importance of free tropospheric
Suppressedentrainmentof the convection.
deep
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convection

NDI‐DI

dry←RH600[%]→humid

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EFFECT OF ENTRAINMENTS

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A‐S Cumulus parameterization
Spectral representation ofcumulus convection
Arakawa and Schubert (1974)

Treatment of entrainments• Arakawa and Schubert (1974):• Chikira and Sugiyama (2010):
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Chikira 2010b
Fraction of detrainments at yeta=0.55 to total

Cumulus congestus related detrainments increases
with the modified GRE entrainment scheme

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Precipitation, SST, and dp/dt500

MIROC5 with Chikira’s implementation of modified GR01 state‐dependent
entrainment to AS parameterization, shows a good performance. Deep
convection is largely suppressed with subsidence over moderately warm
SST regions.
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Precipitation Distributions in TRMM and MIROC‐AGCM
TRMM/HadISST

Atmospheric GCM experimentswith only entrainment
parameter is modified showthat entrainment is essential to
avoid the double ITCZ problem.

CtlNoEnt

AS

09/19/2012神戸大セミナー(Hirota et al., 2012)

Message
To avoid the double ITCZ problem in climate models,a proper treatment of entrainment of thetropospheric air in the cumulus parameterization isessential.
# ただし、SSTバイアスの要因には、積雲のパラメタリゼーションに加えてもうひとつの要素があることが、
CMIP5の解析から示唆されている。 （解析中）
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Derbyshire, S. H. et al. 2004: Sensitivity of moist convection toenvironmental humidity. Q. J. R. Meteorol. Soc., 130, 3055‐3079.
Kuang, Z., and C. S. Bretherton, 2006: A mass‐flux scheme view of ahigh‐resolution simulation of a transition from shallow to deep
cumulus convection. J. Atmos. Sci., 63, 1895‐1909.
Khairoutdinov, M. and D. Randall, 2006: High‐resolution simulation ofshallow‐to‐deep convection transition over land. J. Atmos. Sci. 63,3421‐3436.
Del Genio, A. D., and J. Wu, 2010: The role of entrainment in thediurnal cycle of continental convection. J. Clim. 23, 2722‐2738.

WHAT HAVE BEEN SHOWN FROM CRM STUDIES

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Khairoutdinov and Randall 2006

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Kuang and Bretherton 2006
SAM （CSU)△x: 100m, L256
BOMEXの環境場
水平風のnudging なし
Day2ですでに15㎞高度まで浮力がある↓が、深い対流は抑制されている

shallowcongestus deep

09/19/2012神戸大セミナー

Kuang and Bretherton 2006

Day2.5以降、z>3kmの比湿に下駄：day5の比湿を与える→即座にdeep convectionが発生
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Kuang and Bretherton 2006
Cloudy mass flux
Shallow regime

deep regime

エントレインメント
大エントレインメント
大MSE

MSE
Shallow clouds の方がエントレインメント率が高い。ただ、Deep cloudsも0.125km‐1線を下回らない。Size dependencyの示唆。

09/19/2012神戸大セミナー

Khairoutdinov and Randall 2006

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Khairoutdinov and Randall 2006
CTL

自由大気の加湿一般風なし

Cold Pool なし

感度実験： この実験では、中層はすでに十分湿っていたので、湿度の上乗せにはさほど感度がないが、効果は見える。Cold Poolは大きなBoundary Layer thermalを作ることを通じて、entrainmentの小さい対流を可能にすると解釈。

09/19/2012神戸大セミナー

Del Genio and J. Wu 2010
LBA diurnal cycle
WRF dx: 125m, 600m
Congestus also creats
cold pools
KB06, KR06:
Cold pool convergencecreats larger eddies at
the gust front.

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Suggestion:
Implementation of theGregory(2001)
parameterization
requires a specificationof the initial convective
parcel updrafts speed
enhancement due todowndraft cold poolconvergence.

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CRM studiesから• 中層(>3km)の湿度が深い対流にもたらす効果を確認• エントレインメントのサイズ依存性：浅い雲の方が深い雲より大きい。雲のサイズが大きい方がentrainment小さい。
• ただし、深い（大きい）雲でもentrainmentが0.1を下回らない。
• Congestus（雄大積雲：水雲）でも、cold poolが形成される。
• Cold poolがより大きいplumeの生成を通じて深い対流をトリガーする効果の重要性が指摘された
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まとめ• From long‐term TRMM data, the effect of the large‐scale
subsidence was observationally indicated. It suppresses thedeep convection through drying the mid‐level troposphere,
thus generating cumulus congestus regime of precipitation.
• The “double ITCZ problem” in climate models is closely
linked to the sensitivity of the cumulus parameterization tothe tropospheric humidity.
• Above results are in concert with MIROC5 with the state‐
dependent entrainment rate (Chikira and Sugiyama 2010)• Significant role of cold pools for triggering the deep
convection has been suggested from CRM studies.
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