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

• Slide 1