sensitivity of high-resolution tropical cyclone intensity forecast to surface flux parameterization...
TRANSCRIPT
![Page 1: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/1.jpg)
Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface
Flux Parameterization
Chi-Sann Liou, NRL
Monterey, CA
![Page 2: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/2.jpg)
Uncertainties of Surface Flux Parameterization at High Winds
Current surface parameterization schemes are based upon the similarly theory fitted for wind speed less than 25 ms-1
![Page 3: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/3.jpg)
Black and Chen (2006)
CBLAST**Powell
Donelan
Large & Pond
NWP Model
Drag Coefficient CD
o+□ CBLAST
HEXOS
COARE
![Page 4: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/4.jpg)
Surface Drag Coefficient CD Estimated from Ocean Observations (Jarosz et. al, 2007)
6 Moorings, TC Ivan 9/15/2004
CD Estimated from 3 Different r’s CD Estimated from r=0.02
• Powell Moon et. al
![Page 5: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/5.jpg)
CE/CD:
(for TC growth) Black and Chen (2006)
* * * CBLAST
HEXOS
COARE
NWP model
Critical value (Emanuel, 1985)
![Page 6: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/6.jpg)
Uncertainties of Surface Flux Parameterization at High Winds
==> Conduct numerical experiments to examine the sensitivities of TC intensity forecast to these uncertainties
• Surface Entropy flux (CE/CD at high winds?)
• Surface layer depth at high winds
• Impacts of SST cooling
• Surface Stress (level off at high winds)
Current surface parameterization schemes are based upon the similarly theory fitted for wind speed less than 25 ms-1
![Page 7: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/7.jpg)
Numerical Experiment Resolution:45/15/5km, 30 levels
Dynamics, Numerics:Nonhydrostatic, Fully Compressible (Klemp and Wilhelmson, JAS 1978)Sigma-Z Vertical Coordinate (Gal-Chen and Somerville, JCP 1975)Scheme C grid (Arakawa and Lamb, 1974)Multiple Nested Grids with Movable Inner Meshes (Liou and Holt, 2003)
Precipitation Physics:Grid Scale – Explicit Moist Physics (Rutledge and Hobbs, JAS 1984)Convective – Kain and Fritsch (JAS 1990, JAM 2004)
Boundary Layer: (Level 2.5 TKE Closure)Mixing length – Mellor and Yamada (RGSP 1982) Counter gradient flux – Therry and Lacarrère (BLM 1983 )
Surface Layer:Modified Louis (BLM 1979)
Radiation:Harshvardhan (JGR 1987)
Time-dependent Boundary Conditions:Davies (QJRMS 1976)
Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS®)
![Page 8: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/8.jpg)
0000
63.0*0
2
00*
62*
0
20000
''
''
222*
2
1.0,:
,)(
1092.4,
106.1011.0:
,,))((
,))((
),,(
),(
),,(
000
000
000
00
zzzprescribedzuz
zzug
uz
u
gzR
zzzln
k
zzzln
k
RzzFquqw
RzzFuw
RzzFuuuC
qh
qh
iBhh
zzz
zz
zz
zd
qh
iBqq
iBhh
iB
pointsland
xxpointswater
where
:fluxenergySurface
:stressSurface
h
h
m
COAMPS® Surface Flux Parameterization
Uncertainties at high winds:
• Z0 (or Cd, or U*) ??
• Z0h and Z0q ??
• Formula still good ??
![Page 9: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/9.jpg)
Numerical Experiments
• Model Resolution: 45/15/5 km with moving third mesh
• Forecast length: 48h
• Initial conditions: 3D-Var analysis with 41 bogus data
• Six tropical cyclones (Cat 4 or higher):
Lili (2002), Isabel (2003), Ivan (2004), Maemi (2003), Mindulle (2003), Indian Storm 5 (1999)
1
2
3
4
5
6
![Page 10: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/10.jpg)
(Changes are for water points only)
Set limit to U* when U10 33 ms-1:
U* 1.45 for U10 = 33 ms-1
U* 1.90 for U10 51 ms-1
( U1/2 between 33 to 51 ms-1)
Sensitivity Test 1
Sensitivity Test 2Increase Z0h and Z0q by 10 times
Sensitivity Test 3Set Z0h = Z0q = Z0/10 as over land
CE/CD
![Page 11: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/11.jpg)
Sensitivity Test 5When U10 25 ms-1, SST is
cooled at a rate:
SST = -0.5 oC/day, U10 = 25 ms-1
= -3.0 oC/day, U10 50 ms-1
U2 between 25 to 50 ms-1
(Changes are for water points only)
Sensitivity Test 4When U10 33 ms-1, assume
surface layer is deeper than bottom layer and compute stress at the layer top as:
TB = (sfc+ turb)/2
![Page 12: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/12.jpg)
Averaged Impacts on COAMPS Track and Intensity Forecasts
Impacts of Sensitivity Test 1:
(Limiting Stress)(Control Run Scores)
![Page 13: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/13.jpg)
Averaged Impacts on COAMPS Track and Intensity Forecasts
Impacts of Sensitivity Test 2:
(Z0h*10.)CH/CD = 0.55, u = 40 m/s = 0.48 50 m/s = 0.43 60 m/s
Impacts of Sensitivity Test 3:
(Z0h=0.1*Z0)CH/CD = 0.77, u = 40 m/s = 0.75 50 m/s = 0.74 60 m/s
![Page 14: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/14.jpg)
Averaged Impacts on COAMPS Track and Intensity Forecasts
Impacts of Sensitivity Test 4:
(TB = (sfc+ turb)/2)
Impacts of Sensitivity Test 5:
(SST= -0.5 ~ -3.0oC/day)
![Page 15: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/15.jpg)
Impacts on Indian Storm-5 Forecasts
Track Intensity
![Page 16: Sensitivity of High-resolution Tropical Cyclone Intensity Forecast to Surface Flux Parameterization Chi-Sann Liou, NRL Monterey, CA](https://reader035.vdocuments.site/reader035/viewer/2022062322/56649e4b5503460f94b4084b/html5/thumbnails/16.jpg)
Summary
• Tested uncertainties of surface flux parameterization at high winds have little impacts on the TC track forecast by COAMPS®
• The limit on surface stress and increase of CE/CD have large impacts on the TC intensity forecast by COAMPS®
• Their positive impacts on the intensity forecast almost as large as the negative impact by SST cooling
• The simple average of the stress at the top of the bottom layer has little help in the intensity forecast
• The accurate and balanced initial condition is another area that needs improvement for TC intensity forecast