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中央氣象局全球預報系統積雲參數法之改進與其對於DYNAMO實
驗期間MJO對流之模擬表現
林昌鴻1 楊明仁2 陳建河1
中央氣象局氣象資訊中心1 國立臺灣大學大氣科學系2
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前言
• 本研究將MPAS模式中的new
Tiedtke積雲參數化方案置入至CWB/GFS全球模式，並針對DYNAMO實驗期間的三個MJO事件(2011/10 –
2011/12)進行模擬測試。
• 討論項目:1) new Tiedtke積雲參數化方案內，調整上衝/下衝流逸入率、 積雲
調整時間尺度，對於MJO事件模擬結果的影響。2) MJO對流事件的水氣收支分析研究。
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Numerical model• Model: CWB/GFS (T511L60)• Vertical Coord.: S-P
hybrid 60 layer• Horizontal Coord.: reduced gaussian grid (~25km)•
Model top: 0.1mb
• Cumulus scheme: NSAS, Tiedtke, new Tiedtke(MPAS)• Shallow
convection: NCEP (2010)• Grid scale precipitation: Zhao and Carr
(1997) • Boundary layer: Han and Pan (2011)• Radiation: RRTMG
• Initialized at 2011/10/01, 10/15, 11/01, 11/15, 12/01, 12/15
00Z, respectively• 15-day forecast for each initialization
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Data sets Spatial resolution Temporal resolutionq, u, v,
omega,
LH,OLR precipitation
NCEP/CFSR(Climate Forecast
System Reanalysis)
0.5° 0.5°(64 levels in the
vertical)6-hour
precipitation TRMM 3B42 0.25° 0.25° 3-hour
precipitation GPCP 1° 1° daily
• 2-year time period for 2011-2012
NCEP Reanalysis data:
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time
precipitation anomaly (mm)
GPCP
new Tiedtke (MPAS)NCEP (reanalysis) Tiedtke (CWB)
time
OLR anomaly (W/m2)
NSAS (CWB)
Time-longitude sections (MJO-2 event, 2011/11/15~12/15, 10°S~10
°N average)
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1. decrease the convective adjustment time scale, ∗
• modified adjustment time scale, ∗:
∗ 1
0.14 1.0 500 following Xu and Krueger (1991)
C : convectivecloudfraction: updraft mass flux for deep
convection
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2. decrease the updraft Entrainment rate, ∗
• modified entrainment rate, ∗:
∗ E
⁄ = 5
RH: relative humidity: saturation specific humidity: environment
temperature at cloud base
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reduced new Tiedtke (MPAS)NCEP
GPCP
precipitation anomaly (mm)
OLR anomaly (w/m2)
reduced E
Time-longitude sections (MJO-2 event, 2011/11/15~12/15, 10°S~10
°N average)
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Modified new Tiedtke scheme (nTDK_d)
• Following the WRFv3.8.1 version, the downdraft entrainment
rate is given by
• Downdraft entrainment is modified to decrease with increasing
buoyancy.
2 10 · ·0.5
1
:downdraft mass fluxB: buoyancy
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NCEP (reanalysis) Tiedtke (CWB) new Tiedtke (MPAS) new Tiedtke (
)
OLR anomaly (W/m2)
Time-longitude sections of OLR anomaly (MJO-2 event,
2011/11/15~12/15, 10°S~10 °N average)
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Water budget analysis-- Following Adames and Wallace (2015;
JAS)
• ·• After vertical averaging,
Apparent moisture sink
prime: 20-100-day time scale anomalyL:latent heat coefficient of
evaporationP: precipitationE: evaporation
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(Wm-2)
NCEP_CFSR
TDK
nTDK_d
Contoured: kgm-2
· · · · ·· ′
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warm pool (60°E-180°E , 10°S-10°N ) composite
Color:
· ·
(mm)
Contoured: L · / ( )Vector: 500-1000-hPa-averaged wind
latit
ude
latit
ude
latit
ude
NCEP TDK nTDK_d
· · ·
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·
Contoured: L · ( )Vector: 500-1000-hPa-averaged wind
latit
ude
latit
ude
latit
ude
NCEP TDK TDK_d
·
·
warm pool (60°E-180°E , 10°S-10°N ) composite
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Color: q’
· ′
′
NCEP TDK nTDK_d
warm pool composites (10°S~10°N ) Contoured: / (g )
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′
′
NCEP TDK nTDK_dwarm pool composites (10°S~10°N ) Contoured: / (g
)
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Diabatic heating is dominated by condensational heating in the
Tropics and thus is an indicator of the precipitating cloud
distribution. (Wang et. al. 2017)
NCEP TDK nTDK_d
q
/
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結論 (I)
• 水氣收支分析:1. 使用TDK方案和nTDK_d方案模擬的MJO對流系統於印度洋生成後，
有對流發展過強並於強降水發生後迅速減弱的趨勢，使得MJO對流系統無法維持並橫越海洋性大陸至西太平洋地區。
2. 模擬的MJO對流系統其對流範圍過窄且上衝氣流過強，以及MJO對流系統較無組織性，對流現象呈現隨機生成的特徵。
•
非絕熱加熱垂直分布之分析:nTDK_d參數化方案對於MJO前緣(東側)有過多發展旺盛的淺積雲對流，造成前方水氣無法有效地透過東風平流傳輸至MJO對流中心，使得對流中心水氣較少，系統發展較弱。
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THANK YOUfor your
ATTENTION!
