Differential O2 Absorption Barometric Pressure Radar (DIAR_BAR): Improvements in Tropical Storm Forecasts Qilong Min 1 , Bing Lin 2 , Yongxiang Hu 2 , Wei Gong 1 , Steven Harrah 2 , Wes Lawrence 3 , Dion Fralick 2 , 1 State University of New York, Albany, NY 2 NASA Langley Research Center, Hampton, VA 3 Old Dominion University, Norfolk, VA
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Differential O2 Absorption Barometric Pressure Radar (DIAR_BAR): Improvements in Tropical Storm Forecasts Qilong Min 1, Bing Lin 2, Yongxiang Hu 2, Wei.
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“Simulated satellite SLP” using surface pressure measurements during first landing of Katrina
Model configuration
Advanced Research WRF (ARW) dynamic solver
CCM3 Radiation
Thompson cloud microphysics and Kain-Fristch convective parameterization
Mellor-Yamada PBL
36 and 12 km horizontal resolution and 28 layers, 261×181 grid mesh
84 -hour simulation
276 278 280 28224
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276 278 280 28224
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Case Assimilation Pattern Scale Length Factor
CTL No
Ga Area 0.25-1.00
Gl Lowest Pressure 0.25-1.00
Gc Area without lowest pressure 0.25-1.00
Gb A 2 degree band 0.25-1.00
Sea level pressure (SLP) assimilation (WRF)
e
f
987 993 999 1005 1011 1018 1024
276 278 280 28224
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987 993 999 1005 1011 1018 1024
276 278 280 28224
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987 993 999 1005 1011 1018 1024
276 278 280 28224
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987 993 999 1005 1011 1018 1024
276 278 280 28224
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987 993 999 1005 1011 1018 1024
276 278 280 28224
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987 993 999 1005 1011 1018 1024
276 278 280 28224
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OBS
NCEP-FNL
Gl_.25
Gl_1.0
Ga_.25
Ga_1.0
Sea-Level Pressure at 00 UTC August 26, 2005
Sea level pressure (SLP) assimilation (WRF)
CTL Gl(.25) Ga(1.0)
Ga(1.0)-CTLGl(.25)-CTL
•The assimilation runs symmetrically strengthen the cyclonic flow and enhances the westward and southward mean flow.
•Due to deepening of the hurricane vortex, the convective heating is enhanced
Initial column wind vector (m/s) in the experiments
Ga
Hurricane Katrina tracks
• Single point assimilations have large spread in track when different length scales are used
• All points assimilations have small spread in track and produce close track and landing position
Gl
Thick Black soild—best estimateBlack dashed—CTLSensitivity to scale length factorBlack –1; Red—0.75; Green—0.5 and Black—0.25
900
920
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1000
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Date
Min
SL
P (
hP
a)
Gl(.25)
Gb(.75)
Gc(1.0)
Ga(1.0)
best
12km
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120
150
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Date
Max
Win
d (
Kn
ots
)
Gl(.25)
Gb(.75)
Gc(1.0)
Ga(1.0)
best
12km
Hurricane Katrina Intensity (84-hour: Gl, Ga, Gc and Gb)
Without center pressure, Gc simulates comparable results as Ga, indicating the effect of pressure horizontal distribution in assimilation.
Exp(36km)
Distance (km)
Minimum Pressure (hPa)
Maximum Wind (Knot)
CTL 360 24 49
Ga 71 7 26
Gl 120 11 28
Gb 38 6 28
Gc 66 9 27
Summary
The differential O2 absorption pressure radar will provide the first remote sensing barometric data! The accuracy of instantaneous surface air pressure measurements could be ~4mb. (grid averages: errors ~1mb)
Lab, ground, and flight tests of current prototype instrument indicate that it works
Next generation radar: operational capability This effort will lead significant improvements in predictions of
hurricane intensities and tracks.
This differential O2 absorption radar technique may dramatically extend the current, limited-point barometric capability over oceans with airborne and spaceborne instruments.