deanna hence, stacy brodzik and robert houze university of washington introduction methodology tcsp...
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Deanna Hence Stacy Brodzik and Robert HouzeUniversity of Washington
Introduction
Methodology
TCSP Storms
RAINEX Storms
Combined TCSP + RAINEX Storms
Acknowledgements
We would like to thank Ulrike Romatschke for invaluable assistance in processing this data
TRMM and PMM Grant NAG5-13654 and NNX07AD59G
NASA ESS Grant NNX06AF17H
RAINEX National Science Foundation Grant ATM-0432623
Summary and Future WorkCFAD analysis illustrates the differences in precipitation structure as a function of radius for four major Gulf hurricanes The precipitation in the innermost ring was mostly uniform and intense with evidence of occasional deep convective towers The precipitation was more shallow and stratiform in the middle radii and deeper and more convective at the farthest radii Further CFAD analysis shows little variation in structure from quadrant to quadrant This symmetry is consistent with the low shear environments of all four storms
The CFAD analysis provides a statistical dataset of storm precipitation structure for comparing with high-resolution numerical models
For future work some planned groupings for CFAD generation to expand study to all tropical cyclone basins for all years of TRMM mission (1998-present) include
Storm strength (categories 1-5 on the Saffir-Simpson Scale) Basin (N Atlantic NW Pacific etc) Latitude (Ie 10ordm-15ordm 15ordm-20ordm etc) Analyze sheared storms by quadrants
bull Contour Frequency by Altitude Diagrams (CFADS Yuter and Houze (1995) ) generated by radius annulus quadrant as well as radius and quadrant for each storm overpass
bull Annulus rings are based on the eye diameter (Re) reported by the National Hurricane Center Radius 1 (green) = Re+ 25km Radius 2 (yellow) is 2R1 Radius 3 (orange) is 3R1 and Radius 4 (red) is 4R1 Radius 5 is everything outside of Radius 4
bull Quadrants (white) are determined counter-clockwise from the storm motion vector
bull Cross-section taken along black line
PMM Science Team Meeting Atlanta GA 7 May 2007
Vertical Structure of TCSP and RAINEX Hurricanes as seen by the TRMM PR
Schematic of typical rain pattern as seen by radar according to Willoughby (1988)
Outer eyewall
Inner eyewall
eye
Secondary bands
Pri
nci
ple
ban
d
bull Variation in echo tops from ring to ring is robust result for all 4 storms
bull CFADS that are normalized by height (bottom panels) better emphasize convectivestratiform differences Broad spectrum aloft (esp Ring 5) indicates more convective narrow spectrum (Ring 3) indicates stratiform
bull Ring 1 CFAD defies traditional classifications of ldquoconvectiverdquo (like radius 5) and ldquostratiformrdquo (like radius 3) Its sharp central distribution suggests eyewall slantwise convection has a uniform intense core but the outliers indicate occasional embedded deep convective towers
bull CFADS generated by quadrant (not shown) suggest symmetric structure for all storms in this study consistent with low shear environments of these storms
Non-normalized CFADS for combined Dennis Emily Katrina and Rita overpasses
Ring 1 Ring 3 Ring 5
CFADS for combined Dennis Emily Katrina and Rita overpasses normalized by height
Ring 1 Ring 3 Ring 5
The rain pattern of a tropical cyclone consists of eyewalls and rainbands arranged in patterns like that shown below Interactions of eyewalls and rainbands may affect storm intensity changes but relatively little information exists on the statistics of the vertical structure of these features To better document these vertical structures we compile statistics of the TRMM PR data as a function of distance from storm center
CFADS for all Hurricane Dennis overpasses
Ring 1 Ring 3 Ring 5
CFADS for all Hurricane Emily overpasses
Ring 3Ring 1 Ring 5
1804
Distance (km)
TRMM PR Vertical Slice
12
4
8
16
Hei
gh
t (k
m)
000 451 902 1353
486
432
378
324
270
216
162
108
54
dBZ
eye
TRMM PR Reflectivity at 0336 on 28 August 2005
79degW
51
45
39
33
27
21
dBZ
15
9
3
808190 89 88 87 86 85 84 83 82
RR
LR
25
24 LF
RF
28degN
26
27Storm motion
bull Radial variation of CFADs for RAINEX storms is generally similar to that seen in TCSP stormsmdashseems to be a very robust result
bull Hurricane Katrina has deepest convective tower occurrences of all storms
bull Inner radii precipitation features of RAINEX storms appear to be more intense than corresponding radii in TCSP storms
bull Transitional radii (Radius 2 and 4 not shown) show mixture of features of surrounding radii for all storms
Ring 1 Ring 3 Ring 5
CFADS for all Hurricane Katrina overpasses
Ring 1 Ring 3 Ring 5
CFADS for all Hurricane Rita overpasses
bull Precipitation within Ring 1 (eyewall region) Intense but generally uniform structure (tight gradients) associated with slantwise convection Deep variable outliers suggest some deep convective towers in the eyewall region
bull Precipitation within the middle regions (Ring 3) has shallower (~10 km) heights amp more uniform precipitation with well-defined brightband indicative of stratiform precipitation Characterizes rainbands outside but near eyewall
bull Precipitation in furthest regions are highly variable (broad distribution) Suggests more purely convective precipitation well outside inner-core region
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