Doppler Lidar Winds &
Tropical Cyclones
Frank D. Marks
AOML/Hurricane Research
Division
7 February 2007
NOAA TC Research Goals
Advance understanding and prediction of tropical cyclones (TC)
and other tropical weather by providing resources to address
improvements to forecasts and warnings through use of
observations, observing strategies, analysis, and evaluation. The
goals of this research are to:
1. Advance prediction of TC intensity and structure
change (INTENSITY);
2. Improve prediction of TC track (TRACK);
3. Enhance ability to diagnose and predict impacts of TC on
life and property (IMPACTS); and
4. Improve understanding of and ability to predict TC
frequency and intensity on longer time scales
(SEASONAL).
http://www.aoml.noaa.gov/hrd/
Track
• Sensitivity to environmental circulation beyond TC
envelope
• Current sampling of environment through targeted
observations (dropsondes) and satellite cloud
motion vectors (height assignment).
• HRD (Aberson), NHC (Franklin) and colleagues at
NCEP evaluate utility of observations on track
forecasts.
• Issues include:
• poor data coverage in important areas,
• data assimilation quirks with sparse data
• inability to cover the necessary targets
• temporal and spatial resolution (24 h,
horizontal 100 km, 5-6 layers in vertical)
Synoptic Environment
8
7
65 3
4
1
2
• Need to investigate role
of Saharan Air Layer
(SAL) in early tropical
cyclone development and
intensity change.
• Accomplished 4 NOAA
G-IV research
experiments (SALEX)
into 4 incipient tropical
cyclones (TS Irene,
unnamed TD in 2005 and
TS Debby and Hurricane
Helen in 2006).
Saharan Air Layer Experiment
G-IV Mission 050807n
10
5
15
1
20
26
SAL
NE
SW
NE
SW
Saharan Air Layer Experiment (SALEX)
G-IV Mission 050807n
Polar 1
SAL 2
1
SAL 1
10 15
5
Irene
20
25
200
NW
WNW
NNW
SSE
300
GPS
Sonde
GPS
Sonde
GPS
GPSSonde
Sonde
400
400
GPS Sonde
Jordan
GPS Sonde
E
ES
500
Pressure (hPa)
500
Pressure (hPa)
AEW 1
200
GPS
Sonde
GPS
Sonde
GPS
Sonde
Jordan
Jordan
Jordan
GPS Sonde
Jordan
300
SAL 3
600
700
600
ESE
E
SE
E
700
800
800
900
900
E
NE
ENE
ENE
1000
1000
ENE
NE
NE
NE
0
10
20
30
40
50
RH (%)
60
70
80
90
100
0
5
10
15
Wind Speed (kt)
20
25
30
Intensity/Structure
Vq
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Vr, w
Airborne Doppler-analyzed wind field Hurricane Katrina, 28 September 2005
http://www.aoml.noaa.gov/hrd/Storm_pages/katrina2005/radar.html
Intensity/Structure
170
Wind Speed (kt)
Hurricane Katrina
• Sensitivity
to
environmental
circulation
outside
BEST
TRACK
August
2005
160
Sat (TAFB)
TC
Sat (SAB) eddy flux, etc.)
150 core (shear,
Sat (AFWA)
• Sensitivity
toT-Num
ocean boundary conditions,
140
Obj
AC (sfc)
130
interactions,
and changes along track
AC (flt>sfc)
AC (DVK P>W)
120
• Sensitivity
to inner core dynamics
Surface
110
Drop (sfc)
• Sampling
of these
regions limited by presence of
Drop
(LLM
xtrp)
100
Drop
(MBL xtrp) strong winds. Rely on
heavy
rain,
clouds,
90
whatever
we can get (i.e., radar, in-situ aircraft,
80
satellite:
microwave, IR, and visible)
70
60
• Issues
include:
•50 poor data coverage in important areas,
40
particularly in region surrounding core.
30
•20 temporal and spatial resolution (3-6 h,
8/23horizontal
8/25 5-10 km,
8/27 and 1 8/29
8/31
km vertical)
Date (Month/Day)
Intensity/Structure
• Sensitivity to environmental circulation outside
TC core (wind and pressure field)
• Sensitivity to inner core dynamics (intensity)
• Current sampling of these regions limited by
presence of heavy rain, clouds, strong winds in
the vicinity of the storm. Rely on whatever we can
get (i.e., radar, in-situ aircraft, satellite:
microwave, IR, and visible)
• Issues include:
• poor data coverage in important areas,
particularly in region surrounding core.
• temporal and spatial resolution (6-24 h,
horizontal 50-100 km, at 1-3 layers in
vertical)
How can a Doppler Lidar in
Space help?
Track & Synoptic Environment:
• provide regularly spaced data coverage in important
areas surrounding TC for data assimilation into
numerical models.
• Need temporal resolution at least 12-24 h,
horizontal resolution of 100 km, and vertical
resolution of 1 km.
• Accuracy to better than 1 m s-1 for mean wind
surrounding TC (1 m s-1 error in mean wind yields
86.4 km track error in 24 h).
How can a Doppler Lidar in
Space help?
Intensity:
• improved vertical structure of environment
surrounding and above core, particularly near
tropopause for use in determining shear and eddy
flux.
• higher temporal resolution 6-12 h, horizontal
resolution 25 km, vertical resolution <1 km.
• Accuracy to 1 m s-1 for vertical shear in vicinity of
TC - large differences in storm intensity change for
small changes in vertical shear.
How can a Doppler Lidar in
Space help?
Gale & hurricane force wind radii:
• improved coverage of surface environment
surrounding TC for use in defining wind and
pressure field surrounding storm.
• temporal resolution 12-24 h, horizontal resolution 25
km for gradients, higher vertical resolution in
boundary layer (<1 km).
• Accuracy to better than 1 m s-1 for wind surrounding
TC - 1 m s-1 error in wind yields large error pressure
gradient.
Summary
• Space-based Doppler Lidar can make impact on TC
forecasts and research through improved horizontal
and vertical wind structure in storm environment.
• Doppler Lidar does not need to provide data in core
for significant impact.
• Major advantages:
•
better temporal and spatial data coverage surrounding TC
than currently possible with targeted observations and
satellite cloud motion vectors.
•
higher vertical resolution especially useful near top and
bottom of environment
•
improved accuracy of wind estimates