the effect of latent heat on the extratropical transition of typhoon sinlaku (2008)
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The Effect of Latent Heat on the Extratropical Transition of Typhoon Sinlaku (2008). By: Michael Kevin Hernández. What is an extratropical transition (ET)? Why is this important to study ETs?. 2. What are the current problems in modeling & defining ETs?. - PowerPoint PPT PresentationTRANSCRIPT
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The Effect of Latent Heat on the Extratropical Transition of Typhoon Sinlaku (2008)
By: Michael Kevin Hernández
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• What is an extratropical transition (ET)?
• Why is this important to study ETs?
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3
• What are the current problems in modeling & defining ETs?
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Problem: What is the sensitivity of ET onset and completion to latent heating from the storm and surrounding area?
Hypothesis: The baroclinic processes alone would not suffice to initiate the ET of Typhoon Sinlaku.
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Most extratropical transitions (ET) of tropical cyclones (TC) re-intensify. The area of gale force winds may increase by a factor of 10.
Tropical Storm
Tropical Cyclones
Extratropical Cyclones
Dissipate
~50%
(Hart & Evans 2001; Jones et al. 2003; Guishard 2006)
Other
~10%
~40% 100%
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Extratropical Cyclones can cause loads of localized damage, e.g. 1996 Post-TC Hortense and 2007 Post-TC Noel.
http://www.hurricanecity.com
http://www.hurricanecity.comhttp://www.shunpiking.com
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Even the smallest vortex can trigger and amplify downstream planetary waves.
0 5 10 15 20
2 1 0 -1 -2 Y
[100
0km
]
x [1000km]
Absolute vorticity [10-5s-1]
-2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0
(Riemer 2010)
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Joint Typhoon Warning Center’s Best Track of Typhoon Sinlaku (2008)
Sept. 7
Sept. 9
Sept. 12
Sept. 14
Sept. 17
Sept. 19
Sept. 20 Sept. 21Sept. 18
Case study:
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ECMWF best track and model ensemble members of Sinlaku, but with perturbed initial conditions.
Sept. 2008
latit
ude
longitude
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Small perturbations in the initial conditions lead to huge differences in the interaction of the cyclone and the trough.
ensemble member 4
latit
ude
longitude
ensemble member 8
ensemble member 21
ensemble member 5
ensemble member 10
ensemble member 9
72 hour forecast
Hart (2003) definition: Cyclone Phase Space on ECMWF analysis of Typhoon Sinlaku.
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ET onset
ET completion
120 140 160 180
40
20
Baro
clin
city
(B)
100
50
0
-50
Thermal wind at 900-600 hPa (-VLT)
-300 -200 -100 0 100 200 300
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Assuming Hart (2003) definitions of ET onset and completion, a 50 member ensemble forecast model still cannot pinpoint the ET process temporally.
Sept. 13 Sept. 14 Sept. 15 Sept. 16 Sept. 17 Sept. 18 Sept. 19 Sept. 20 Sept. 21 Sept. 22
ECMWF 50 member ensemble for ET onsetECMWF 50 member ensemble for ET completion
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There is no universal definition for ET onset or completion.
ECMWF analysis
ECMWF analysis
Japan Meteorological Agency
Joint Typhoon Warning Center
Joint Typhoon Warning Center
Klein et al. (2000) analysis
Klein et al. (2000) analysis
Japan Meteorological Agency
Sept. 13 Sept. 14 Sept. 15 Sept. 16 Sept. 17 Sept. 18 Sept. 19 Sept. 20 Sept. 21 Sept. 22
Onset
Completion
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Another method for the ET definition is defined by Klein et al. (2000), which uses satellite analysis.
17 Sept 0930 UTC CIRRUS EDGE
POSSIBLE WARM FRONTOGENESIS
EYEWALL EROSION
DRY SLOTDRY SLOT
18 Sept 1130 UTC
19 Sept 1830 UTC
ET onset: 17 Sept 0800 UTCET completion: 19 Sept 1800 UTC
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Question:
What is the sensitivity of extratropical transition onset and completion to latent heating from the storm and surrounding area?
Hypothesis:
The baroclinic processes alone would not suffice to initiate the extratropical transition of Typhoon Sinlaku.
Experiments:
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• WRF (ARW core) V3.0.1 model• Physics (FULL)• 9 km (outer) domain: Kain–Fritsch cumulus
parameterization • 3 km (inner) domain: convection is explicitly resolved
• Physics (Fake Dry Tropical Cyclone - FDTC)• Same as FULL but:• No cumulus parameterization on any domain • Latent heating turned off in the microphysics
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We would want the domain to be from 15-65oN & 120-175oE
longitude
latit
ude
The ideal domain didn’t produce ideal results.
latit
ude
longitude
Moving the domain further south still meant that the trough was still in the domain. But not by much.
latit
ude
longitude
Now the boundaries are feeding a some information about the trough into the simulation.
latit
ude
longitude
There is a lot more information of the trough that is no longer explicit.
latit
ude
longitude
Feeding in the information of the entire trough isn’t producing ideal results either.
latit
ude
longitude
Domain size:
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– First (static) domain:• 740 × 430 points at 9 km horizontal
resolution• centered at 33N and 150E• 36 vertical levels
– Second (vortex following) domain:• 330 × 330 points at 3 km horizontal
resolution• 36 vertical levels
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Varying the physics parameterizations, while keeping the northern boundary at 50oN, led to differences in TC track and intensity.
Tracks
JTWC
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Latent heating affects whether the TC dies early, follows the best track, and the intensity of the storm.
Tracks
JTWC best trackMin pressure [hPa]
pres
sure
over land
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Deep layer mean (DLM) winds influence TC tracks and the DLM in each simulation varies: 900-200 hPa layer for FULL; 800-500 hPa layer for FDTC. While the JTWC best track is the arrow in black.
FULL
FDTC
1: The synoptic flow pattern at 700-200 hPa was influenced by a lack of latent heating.
FULL FDTC17 Sept
18 Sept
19 Sept
50o
40o
30o
20o
50o
40o
30o
20o
50o
40o
30o
20o
120o 140o 160o 175o 120o 140o 160o 180o
H H
2: The synoptic flow pattern at 700-200 hPa was influenced by a lack of latent heating.
FULL FDTC
20 Sept
21 Sept
19 Sept
50o
40o
30o
20o
50o
40o
30o
20o
50o
40o
30o
20o
120o 140o 160o 175o 120o 140o 160o 180o
H
H
H
H
H H
8070
60
50
4030
2010
0Sept. 17 18 19 20 21
FULL case: TC weakens (KE decrease) once the 500 hPa trough has passed by.
HH H
50o
40o
30o
20o
120o 140o 160o 175o 120o 140o 160o 175o 120o 140o 160o 175o
m2 S
-2 a
rea-2
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8070
60
50
4030
2010
0Sept. 17 18 19
FDTC case: TC weakens still (KE decreases) even as the 500 hPa trough has passed by.
50o
40o
30o
20o
120o 140o 160o 175o 120o 140o 160o 175o 120o 140o 160o 175o
H H H
m2 S
-2 a
rea-2
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The core of the storm within 6 hours and out between both simulations also are influenced by latent heat.
+6 hrs
17 Sept 00 UTC
17 Sept 06 UTC 20 Sept 12 UTC
17 Sept 06 UTC 18 Sept 12 UTC
First 6 hrs
+30 hrs
+78 hrs
FULL
FDTC
weak core
cold air seclusion
warm frontogenesis
cold
frontogenesis
strong core
banding
Near the end of the TC life
+6 hrs
Near the end of the simulation
In summary, modeling ET of TC is hard even if we had a universal definition.• Tracks • Dynamically
• Temporally
• Boundary placement • Choice of model physics
Sept. 13 Sept. 14 Sept. 15 Sept. 16 Sept. 17 Sept. 18 Sept. 19 Sept. 20 Sept. 21 Sept. 22
ECMWF 50 member ensemble for ET onsetECMWF 50 member ensemble for ET completion
Latent heating is needed to maintain the TC and allow the TC to undergo ET.
• Synoptics
• KE
19 Sept21 Sept
w/ latent heat w/o latent heat
• Inner core
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Future work:
Questions?
• Two more new simulations: 1) Remove TC with FULL Physics 2) Remove TC with FDTC Physics
• FDTC simulation suggests an opportunity to explore the evolution of the 500 hPa trough in the absence of TC and Latent Heating.
Hypothesis: ConfirmedThe baroclinic processes alone would not suffice to initiate the extratropical transition of Typhoon Sinlaku.
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Supplementary slides
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Varying the physics parameterizations, while keeping the northern boundary at 50oN, led to differences in TC track and intensity.
Physics set name Microphysics SW radiation PBL Similarity
theoryCumulus scheme
GKF Goddard Goddard Pleim-Xu Pleim-Xu Kain-Fritsch
GGD Goddard Goddard Pleim-Xu Pleim-Xu Grell-Devenyi
WSM5KF WSM 5 class Goddard MYJ ETA Kain-Fritsch
WSM6KF WSM 6 class MM5 YSU MM5 Kain-Fritsch
WSM6GD WSM 6 class MM5 YSU MM5 Grell-Devenyi
Hernandez et al. (‘09) WSM 5 class Goddard YSU MM5 Kain-Fritsch
track differences
JTWC
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Model Configurations:• WRF (ARW core) V3.0.1• Physics (FULL)
• WSM 5 class microphysics• Goddard SW radiation• RRT LW radiation• 5-layer thermal diffusion Land-surface • MYJ PBL• ETA Surface Model• KF Cumulus parameterization
• turned off for domains with resolution exceeding 5 km
• Physics (FDTC)• Same as FULL but
• No cumulus parameterization• Latent heating turned off in the microphysics
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How I calculated the Deep layer mean (DLM) winds.
FULL
FDTC
Z = 0
Z = h
…weighted average