![Page 1: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/1.jpg)
A Numerical Study of a TOGA COARE Super Cloud Cluster –
Preliminary results
Peter M.K. Yau and Badrinath Nagarajan
McGill University
![Page 2: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/2.jpg)
Outline
•Motivation & Objectives•Case Overview•Modeling Strategy•Results & Conclusions•Future work
![Page 3: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/3.jpg)
Motivation• MJO associated with supercloud clusters.
Processes organizing warm-pool convection a “zeroth-order problem” (Webster & Lucas 1992)
• Organizing mechanisms (OM) particularely at meso-and synoptic scale not well understood (Yanai et al 2000, Gabrowksi 2003).
• Improved understanding of OM on various scales should lead to:– better representation of convection in models– reduced forecast errors at the medium range – better representation and understanding of the
role of convection on water vapor distribution in the vertical
![Page 4: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/4.jpg)
Objective Use a real data multi-grid (15-5-1 km)
numerical modeling approach to• simulate supercloud clusters (SCCs)
over TOGA COARE• diagnose the processes that:
– organize MCSs,– cause clustering of MCSs, and
• study the impact of convection on water vapor distribution in the vertical
![Page 5: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/5.jpg)
Case Overview – IOP of TOGA COARE
Yanai et al (2000)
OLR (W m-2)•Once a day•Averaged 5S - 5N
•OLR < 215 W m-2
Shaded
•Focus of this study on SCC A
1Nov 92
28 Feb 93
1Dec 92
1Jan 93
1Feb 93
![Page 6: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/6.jpg)
IFA
Longitude
Tim
e
Time cluster
MCSs
Time cluster:•Lifetime > 24 h
MCS:•Lifetime < 24 h
The 6 DEC. 92 – 6 JAN. 93 SUPER CLOUDCLUSTER
Data Used:•Hourly GMS Infrared data•0-10S average
•Areas < 235 K precipitating (GATE/COARE convection)
![Page 7: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/7.jpg)
EVOLUTION of IFA time cluster (11-13 DEC 92)
Data Used:•Precipitation retrieved from SSM/I, VIS/IR satellite data Sheu et al (1996), Curry et al (1999)•3 hourly/ 30 km resolution
mm h-1
![Page 8: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/8.jpg)
mm/h
Data Used:•Precipitation retrieved from SSM/I, VIS/IR satellite data Sheu et al (1996), Curry et al (1999)•3 hourly/ 30 km resolution
EVOLUTION of IFA time cluster (11-13 DEC 92)
![Page 9: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/9.jpg)
Madden & Julian (1994)
Schematics of Nakazawa (1988)
![Page 10: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/10.jpg)
IFA
Longitude
Tim
e
1
2
3 4
5
6
7
89
1011
12 13
14
15
16
Time cluster:•Lifetime > 24 h
Westwardpropagating
Eastwardpropagating
Propagation of Time Clusters
![Page 11: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/11.jpg)
IFA
Longitude
Tim
e
1
2
3 4
5
6
7
89 1
011
12
1314
15
16
Westward propagating Eastward propagating
IFA
200 hPaPROPAGATION OF TIME CLUSTERS
![Page 12: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/12.jpg)
Time Evolution of Domain Average Brightness Temperature
Early morning minimum
Afternoon minimum(land)
Afternoon minimum(ocean)
![Page 13: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/13.jpg)
• Brightness temperature minimum occurs: –Early morning for 8 time clusters,
–Afternoon for 4 time clusters • Suggests that most of the time
clusters are indeed MCSs
![Page 14: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/14.jpg)
Organizing Mechanisms
• Large scale flow features (e.g., 2-day waves)
• Vertical wind shear (Le Mone et al 1999)
• Mid-level mesovortices (Nagarajan et al 2004) – Dec. 15, 1992
• Mapes gravity-wave mechanism
![Page 15: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/15.jpg)
Longitude
Tim
e
1
2
3 4
5
6
7
89
1011
12 13
14
15
16
Westward propagating Eastward propagating
IFA
TIME CLUSTERS & 2-DAY PERIODICITY
K
1-4, 7-9, 11-13associated with2-day wave (Chen et. al 1996,Takayabu et. al 1996)
![Page 16: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/16.jpg)
TIME CLUSTERS & VERTICAL SHEAR* (wind speed)
DATE 1000-850 hPa
800-400 hPa
6 – 19 Dec. 9228 - 31 Dec. 921, 4-6 Jan. 93
< 3.0 m s-1 < 5.0 m s-1
20 - 28 Dec. 92
> 3.0 m s-1 > 5.0 m s-1
27 Dec. 922-3 Jan. 93
< 3.0 m s-1 > 5.0 m s-1
*Areal & Temporal AveragesTemporal average: Duration of the time clusterAreal average: 0-10S, longitudinal extent of time cluster
![Page 17: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/17.jpg)
SummaryDuring the lifetime of the SCC (6Dec-
6Jan):• Identified 16 time clusters consisting
of eastward & westward propagating cloud clusters.
• Convection generally associated with 2-day wave activity
• Convection occurred in a weak vertical wind shear environment except between 20-28 Dec 1992.
![Page 18: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/18.jpg)
The Model
• Canadian mc2 model (Benoit et al. 1997)
• Fully compressible equations• Semi-Lagrangian, semi-implicit
numerics• One-way nesting of lateral boundary
conditions• RPN1 physics package
1 Recherche en Prevision du Numerique
![Page 19: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/19.jpg)
1-month long time series
00 UTC/6 Dec. 92
03UTC/7 Dec. 92
00 UTC/7 Dec. 92 03 UTC/8 Dec. 92
00 UTC/6 Jan. 93
Time series based on last 24 h of each 27h long simulation.
•00 UTC chosen because of high availability of rainfall data for assimilation •Time integration strategy follows guichard et al. (2003)
![Page 20: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/20.jpg)
3900 km
3900 km
130E 160E 190E
10N
EQ
10S
MC2 MODEL DOMAIN
Grid Size: 549 x 279 x 40, Horizontal grid length: 15 kmModel Top: 26 km
IFA
![Page 21: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/21.jpg)
Modeling Strategy• Model Parameters:
– KF CPS (deep convection), BM CPS (shallow convection), Kong and Yau (1997) explicit bulk 2-ice microphysics, time step(90 s)
• Initial Conditions:– ECMWF operational analysis (0.5 o)
enhanced:• radiosonde data (Cieleski et al 2003), • temperature & moisture profiles modified
by 1D-VAR rainfall rate assimilation scheme (Nagarajan et al. 2006) and
• ABL moistening due to diurnal SST warming (Nagarajan et al 2001, 2004).
• 6-hourly lateral boundary conditions
![Page 22: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/22.jpg)
IFA averaged surface precipitation rate
Missing data
![Page 23: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/23.jpg)
IFA averaged surface sensible and latent heat flux
![Page 24: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/24.jpg)
Horizontal size distribution of clouds (Model Domain)
Wielicki & Welch (1986)
Missing data
![Page 25: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/25.jpg)
Domain-averaged surface precipitation rate (140-180E, 0-10S)
Missing data
![Page 26: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/26.jpg)
RH
(h)
Heig
ht
(km
)IFA Av. RH
![Page 27: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/27.jpg)
• The IFA-mean and temporal variability of:– surface fluxes of latent and sensible heat,
surface precipitation reasonable
• Large scale :– Simulated surface precipitation overpredicted– Horizontal size of cloud clusters are reasonably
simulated.
• Month long mesoscale simulation captures reasonably the life cycle of the super cloud cluster.
Conclusions
![Page 28: A Numerical Study of a TOGA COARE Super Cloud Cluster – Preliminary results](https://reader035.vdocuments.us/reader035/viewer/2022062518/56814bfc550346895db8f82b/html5/thumbnails/28.jpg)
Future Work• Nesting to higher resolutions (5 km
and 1 km) with new three-moment 4 - ice microphysics (Milbrandt and Yau 2005a,b)
• Diagnose mechanisms that organized the super cloud cluster
• Diagnose processes for water vapor and temperature distributions