Transcript 100509Tucson_TropConf_Hence.ppt

Vertical distribution of radar reflectivity in
eyewalls observed by TRMM
AMS
Hurricane
and Tropical
Meteorology
Conference
Tucson
May 9, 2010
Deanna A. Hence and Robert A. Houze, Jr.
University of Washington
Idealized vertical structures
suggested by past studies
Outer
rainband
Deep
Inner
rainband
Restricted
Inner
rainband
Deep
Outer
rainband
How does the eyewall structure change
with storm evolution and environmental
conditions?
From Houze et al. (2007)
Primary Analysis Tools
• Contoured
Frequency by
Altitude Diagrams
(CFADs)
Yuter and Houze 1995,
Houze et al. 2007
Relative frequency of occurrence
• NCAR Zebra software
From NASA TRMM website
(http://trmm.gsfc.nasa.gov/)
• TRMM Precipitation
Radar (PR)
Annuli and Quadrant Analysis
TRMM PR Maximum Reflectivity at
03:26 on 28 August 2005
UL
Reflectivity (dBZ)
UR
From the National
Hurricane Center
(NHC) best track data
• Center location
• Eye diameter
DR
DL
• Storm motion
Raw Number CFADs, Not Normalized,
All Overpasses
DR
DL
120
Shear
peak of low-level
distribution
60
UL
UR
10
How shear affects the eyewall
UL
DL
shear
UL
UR
DL
DR
UR
DR
From Black et al. (2002)
From Braun et al. (2006)
Updrafts initiating just upwind of the downshear-left quadrant
Vertical structure in weaker and
stronger storms
CAT1,2
CAT4,5
Total Eyewall Annulus, Normalized
• Greater reflectivity overall
• More extreme outliers
 intermittent intense cells
Vertical structure over cooler and
warmer water
Marginal SST
(26-28 °C)
High SST
(>28 °C)
Total Eyewall Annulus, Normalized
• Majority of distribution
similar
• Outliers much stronger
and higher in high SST
cases
Vertical structure by quadrant
relative to shear
Normalized CFADs, All Overpasses
DR
DL
Brightband
appears
No brightband,
broad upper levels
Shear
1.0
0.5
UL
UR
Brightband
intensifies
Weaker overall,
no distinct peak
0.2
Normalized CFADs, High SST
DL
DR
Tighter Distribution
Weakening
More distinct
brightband
Shear
1.0
0.5
UL
Weakening
UR
Strengthening
0.2
Conclusions
• Vertical wind shear
• Determines echo placement around the eyewall
• Cat. 4 and 5 storms
• More intense
• More intermittent intense cells
• Lower SST values
• Suppress intense outliers
• Doesn’t change the mean reflectivity distribution
• Track motion ≥ shear, opposite in direction
• echo formation region shifts upshear right
Ongoing Work
• Expand analyses to rainband and outer
regions
• Expand analyses to intense cyclones in
worldwide basins
Normalized CFADs, High SST
DL
DR
Tighter Distribution
Weakening
More distinct
brightband
Shear
1.0
0.5
UL
Weakening
UR
Strengthening
0.2
Normalized CFADs, Low Shear
DL
DR Narrowing of upper levels
Tighter Distribution
More distinct
brightband
Shear
1.0
0.5
Weakening
UR
Strengthening
0.2
Track
UL
This research was supported by
NSF Grant ATM-0743180 and NASA Grants NNX07AD59G and NNX10AH70G