Deanna Hence, Stacy Brodzik and Robert Houze University of Washington

1
Vertical Structure of TCSP and RAINEX Hurricanes
as seen by the TRMM PR
Deanna Hence, Stacy Brodzik and Robert
HouzeUniversity of Washington
CFAD 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 (I.e. 10º-15º, 15º-20º, etc.)

?
Analyze sheared storms by quadrants
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.

• 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.
• Precipitation within the middle regions (Ring 3)
  has shallower (10 km) heights more uniform
  precipitation with well-defined brightband,
  indicative of stratiform precipitation.
  Characterizes rainbands outside but near eyewall.
• Precipitation in furthest regions are highly
  variable (broad distribution). Suggests more
  purely convective precipitation well outside
  inner-core region.

• Variation in echo tops from ring to ring is
  robust result for all 4 storms.
• CFADS that are normalized by height (bottom
  panels) better emphasize convective/stratiform
  differences. Broad spectrum aloft (esp. Ring 5)
  indicates more convective narrow spectrum (Ring
  3) indicates stratiform.
• Ring 1 CFAD defies traditional classifications of
  convective (like radius 5) and stratiform
  (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.
• CFADS generated by quadrant (not shown) suggest
  symmetric structure for all storms in this study,
  consistent with low shear environments of these
  storms.

• Radial variation of CFADs for RAINEX storms is
  generally similar to that seen in TCSP
  stormsseems to be a very robust result.
• Hurricane Katrina has deepest convective tower
  occurrences of all storms.
• Inner radii precipitation features of RAINEX
  storms appear to be more intense than
  corresponding radii in TCSP storms.
• Transitional radii (Radius 2 and 4, not shown)
  show mixture of features of surrounding radii for
  all storms.

• 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.
• 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.
• Quadrants (white) are determined
  counter-clockwise from the storm motion vector.
• Cross-section taken along black line

PMM Science Team Meeting, Atlanta, GA, 7 May 2007