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Deep moist atmospheric convection in a sub‐kilometer global simulation
Yoshiaki Miyamoto, Yoshiyuki Kajikawa, Ryuji Yoshida, Tsuyoshi Yamaura, Hisashi Yashiro, Hirofumi Tomita
(RIKEN AICS)
I. BackgroundII. Experimental SettingsIII. Methodology for
detection of convectionIV. ResultsV. Conclusion
戦略分野3メソ課題研究会 March 7th, 2014 @Kobe
I. BACKGROUND
Byers and Braham (1949)
※deep moist convection := ”Convection”
Convection
Convection• Element of cloudy disturbances• Transport heat and moisture
Horizontal scale (x) 〜100 km
hard to explicitly solve in global models(x〜101 – 102 km)
←cumulus parameterization
2000〜Model development +enhancement of computer power => x 〜 100 km→clouds are explicitly solved in global models Still coarser or comparable to obs.
Regional model (Weismann et al., 1997) : Change around Δx <= 4 km
~100 km
~100 kmHeat & Moisture
Byers and Braham (1949)
Objective:
Reveal the dependence of the simulated convection on resolution in global model by describing the global statistical characteristics.
Experimental design
model NICAM (Tomita and Satoh 2004, Satoh et al. 2008)
Initial state 3‐day integrated results of 1‐step coarser resolution
SST NCEP analysis + nudging (Reynolds weekly SST)
land Model adjusted produced by 5 year run
Cloud physics NSW6 (Tomita 2008)
Boundary layer turbulence MYNN (Nakanishi and Niino 2004, Noda et al. 2008)
Surface flux Louis (1979)
Long and short‐wave radiation MSTRNX (Sekiguchi and Nakajima 2008)
Cumulus parameterization ‐‐
integration period(12 h)Δx
※72 h integration before producing initial fields
Computational Cost
• Nodes used: 20480 (~160000 cores)
• Wall-clock time: 53 h
• Sustained performance: 7~8 %
• Storage: 200 TB
integration period(12 h)Δx
※72 h integration before producing initial fields
Δ14.0 km
Δ3.5 km
Δ0.87 km
Δ7.0 km
Δ1.7 km
Snap shot of OLR12‐h integrations
II. METHOD OF DETECTING CONVECTION1. Detect “convective grids” by ISCCP table
2. Determine “convective core” grids
(Rossow and Schiffer 1999)
Step 1/2: Detect convective grids by ISCCP table
Δx = 14 km
Step 2/2: determine convective core grids
a) ISCCP convective grids ( )
d) Convective grids ( ) := where vertically aved w is larger than those at surrounding 8 grids
b) Find grids ( ) at which all the surrounding 8 grids satisfy the ISCCP condition
c) Estimate horizontal gradient of vertical velocity averaged vertically in the troposphere
example(Δx=3.5 km)
w(troposphere mean)CI = 0.1 m s‐1w = 0.1 m s‐1
ISCCP convective gridConvection core grid
Δx = 3.5 km
Δx = 14 km
Δx = 7 km Δx = 1.7 km
w(troposphere mean)CI = 0.1 m s‐1w = 0.1 m s‐1
ISCCP convective gridConvection core grid
III. RESULTS Δ0.87 km
Composited structure of convection (GL13)
Convection core grid ※transform the coordinate into the cylindrical around the core gridmean of all the detected convectionsymmetric around the x axis
Composite of convection (vertical velocity)
Δx ≧ 3.5 km:– Convection is represented at 1
grid– Little dependence on resolution
Δx ≦ 1.7 km:– Convection is represented at
multiple grids– Intensify w/ resolution
Δ14.0 km Δ7.0 km Δ3.5 km Δ1.7 km Δ0.87 km
※transform the coordinate into the cylindrical around the core gridmean of all the detected convectionsymmetric around the x axisX axis is normalized by resolution
0 4 5 100
0.05
0.1
0.15
0.2
0.25
number of gird
frequ
ency
/tota
l num
ber
(b) distance between convection
14.07.03.51.70.8
0.8 1.7 3.5 7 14103
104
105
(a) number of convection
(km)
num
ber
Number and distance of convection
Δx ≧ 3.5 km:
– number: increase by factor of 4
Δx ≦ 1.7 km:
– number: decrease in increasing rate
– distance: 4 grids
– distance: 5 grids
Summary
Global simulation with a sub-kilometer resolution
Finding Convection features (structure, number, distance)
change between Δ3.5 km Δ1.7 km- Δx should be 2.0〜3.0 km to resolve convection in global models
1.7 km3.5 km
Thank you very much for your attention!
Miyamoto, Y., Y. Kajikawa, R. Yoshida, T. Yamaura, H. Yashiro and H. Tomita, 2013: Deep moist atmospheric convection in a sub-kilometer global simulation, Geophysical Research Letters, 40, 4922-4927.
Special thanks to Drs. H. Miura, S. Iga, S. Nishizawa, M. Satoh, our colleagues, and two anonymous reviewers for fruitful discussions. The authors are grateful to researchers and technical experts at RIKEN and FUJITSU for their kind help. The simulations were performed using the K computer at the RIKEN Advanced Institute for Computer Science.
SUPPLEMENT
What is the general characteristics of convection?
• Resolution dependence Weismann et al. (1997): dependence of squall line
(Klemp and Wilhelmson (1979) cloud model)- Characteristics changes Δx less than and
equal to 4 km
Jorgensen&LeMone (1989)
コア
の直
径(km)
存在頻度 (積算)
1
15
Is there any threshold of resolution in realistic conditions?
Weismann et al. (1997)
w’’ w’u’ qr
http://callofduty.wikia.com/wiki/File:Cumulonimbus.jpg
Jorgensen and LeMone (1989): 50% of convection (core) has horizontal scale less than 1 km
• Isolated convection
– Element of amospheric cloudy disturbances
– Transport of heat/moisture
What is the general characteristics of convection?
Model(NICAM, Tomita & Satoh 2004, Satoh et al. 2008)
Global cloud-system resolving model
Icosahedral grid
nohydrostatic DC
explicit cloud expression:
21
Miura et al. (2007)
解析範囲:130—190E, ‐15—15N
0 1 2 3 4 5
0.8 1.7
3.5 7
14 30
a r e a ( 1 0 - 6 k m 2 )
Delta x (km)
area icp cutoff (GL08-12 t=201208250600)
0
0.02
0.04
0.06
0.08 0.1
0.8 1.7
3.5 7
14 30
a r e a ( 1 0 k m )
Delta x (km)
area con cutoff (GL08-12 t=201208250600)
0 10 20 30 40 50
0.8 1.7
3.5 7
14 30
a r e a ( 1 0 - 6 k m 2 )
Delta x (km)
area icp cutoff (GL08-12 t=201208250600)
面積
0 2 4 6 8 10
0.8 1.7
3.5 7
14 30
m a s s f l u x ( x 1 0 3 k g m - 2 s - 1 )
Delta x (km)
areal ave. (all) of z-aved mass flux (GL08-12 t=2012082506
allaveallave
解析範囲:130—190E, ‐15—15N
0 50
100
150
200
250
300
350
400
0.8 1.7
3.5 7
14 30
m a s s f l u x ( x 1 0 3 k g m - 2 s - 1 )
Delta x (km)
areal ave. (con) of z-aved mass flux (GL08-12 t=201208250
conaveconave
0 50
100
150
200
0.8 1.7
3.5 7
14 30
m a s s f l u x ( x 1 0 3 k g m - 2 s - 1 )
Delta x (km)
areal ave. (icp) of z-aved mass flux (GL08-12 t=2012082506
icpaveicpave
面積平均質量フラックス
0 1 2 3 4 5
0.8 1.7
3.5 7
14 30
p r e c i p i t a t i o n ( x 1 0 3 m m h - 1 )
Delta x (km)
areal ave. (icp) of rain flux (GL08-13 t=201208250600)
icpaveicpave
0 2 4 6 8 10
0.8 1.7
3.5 7
14 30
p r e c i p i t a t i o n ( x 1 0 3 m m h - 1 )
Delta x (km)
areal ave. (icp) of rain flux (GL08-13 t=201208250600)
conaveconave
0
0.05 0.1
0.15 0.2
0.8 1.7
3.5 7
14 30
p r e c i p i t a t i o n ( x 1 0 m m h )
Delta x (km)
areal ave. (all) of rain flux (GL08-13 t=201208250600)
allaveallave
解析範囲:130—190E, ‐15—15N
面積平均降水量
100
120
140
160
180
200
220
240
0.8 1.7
3.5 7
14 30
m a s s f l u x ( x 1 0 3 k g s - 1 )
Delta x (km)
area-integrated (all) z-aved mass flux (GL08-13 t=201208250
alltotalltot
0 5 10 15 20
0.8 1.7
3.5 7
14 30
m a s s f l u x ( x 1 0 3 k g s - 1 )
Delta x (km)
rea-integrated (con) z-aved mass flux (GL08-13 t=20120825
contotcontot
100
120
140
160
180
200
220
240
0.8 1.7
3.5 7
14 30
m a s s f l u x ( x 1 0 3 k g s - 1 )
Delta x (km)
area-integrated (icp) z-aved mass flux (GL08-13 t=20120825
icptoticptot
解析範囲:130—190E, ‐15—15N
面積積分質量フラックス
0 1 2 3 4 5
0.8 1.7
3.5 7
14 30
p r e c i p i t a t i o n ( x 1 0 3 m m h - 1 m 2 )
Delta x (km)
area-integrated (icp) of rain flux (GL08-13 t=20120825060
icptoticptot
0
0.05 0.1
0.15 0.2
0.8 1.7
3.5 7
14 30
p r e c i p i t a t i o n ( x 1 0 m m h m )
Delta x (km)
area-integrated (con) of rain flux (GL08-13 t=20120825060
contotcontot
解析範囲:130—190E, ‐15—15N
0 1 2 3 4 5
0.8 1.7
3.5 7
14 30
p r e c i p i t a t i o n ( x 1 0 3 m m h - 1 m 2 )
Delta x (km)
area-integrated (all) of rain flux (GL08-13 t=20120825060
alltotalltot
面積積分降水量
200
210
220
230
240
250
0.8 1.7
3.5 7
14 30
O L R ( W m - 2 )
Delta x (km)
areal ave. (all) OLR (GL08-13 t=201208250600)
allall
100
110
120
130
140
150
0.8 1.7
3.5 7
14 30
O L R ( W m - 2 )
Delta x (km)
areal ave. (con) OLR (GL08-13 t=201208250600)
concon
100
110
120
130
140
150
0.8 1.7
3.5 7
14 30
O L R ( W m - 2 )
Delta x (km)
areal ave. (icp) OLR (GL08-13 t=201208250600)
icpicp
解析範囲:130—190E, ‐15—15N
面積平均OLR
東西風速・降水量・海面更正気圧の緯度分布
• 各解像度間に大きな差無し
• 解析値・観測値との顕著な差無し
東西風速 降水量
海面更正気圧
Skamarock (2004)
Effective resolution (~ 6-7Δx):
それより小さい空間スケールの現象が、モデルで計算される運動エネルギースペクトルが-5/3則から外れる解像度
• 実現象で対流の存在する間隔 < 6-7Δx
– モデルでは現象と同様の間隔を再現できない
→Effective resolution以上で、且つ、実現象に最も近いスケール(=6-7Δx)に最頻値が出現
• 実現象で対流の存在する間隔 > 6-7Δx
– モデルで対流間の距離を解像可能
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