# Presentation: 169132

## The 3-D Reflectivity Structure of Intense Atlantic Hurricanes as seen by the TRMM PR

- Deanna Hence, Robert Houze and Stacy Brodzik
- University of Washington

- 2008 TRMM Conference

- February 5th, 2008

## Objectives of the Study

- To develop a three-dimensional climatology of  precipitation structures within tropical cyclones
- To characterize the dynamics of the rainbands—are they more like ordinary convection or eyewall convection?

- 2008 TRMM Conference

- February 5th, 2008

**Notes:**
Should be plural--objectives

## Statistics of Precipitation Structure

- Suggest higher reflectivities aloft in eyewall and outer rainband region
- More intense brightband signature in inner rainband region

- Contoured Frequency by Altitude Diagrams (CFADS, Yuter and Houze 1995)
- Show frequency of occurrence of reflectivity values as a function of height
- Distinguishes precipitation type and vertical structure

- Yuter and Houze (1995)

- Cecil et al. (2002)

- 2008 TRMM Conference

- February 5th, 2008

## Annuli and Quadrant Definition

- Based on eye diameter
- Ring 1 = Reye + 17 km
- Ring 2 = 2R1
- Ring 3 = 3R1
- Ring 4 = 4R1
- Quadrants counted counterclockwise from storm track vector

- 2008 TRMM Conference

- February 5th, 2008

## TCSP and RAINEX

- Initial study includes Hurricanes Dennis, Emily, Katrina, and Rita of 2005
- Analysis of overpasses when storms are hurricane strength
- Quadrant analysis revealed lack of consistent asymmetry

- 2008 TRMM Conference

- February 5th, 2008

## Outer Region

- Broad distribution of reflectivities below melting level
- Bright band signature
- Relatively broad distribution above melting level reaching to 11 km
- Resembles ordinary buoyant convection

- 2008 TRMM Conference

- February 5th, 2008

## Middle Region

- Narrower distribution of reflectivity below melting level
- Strong brightband signature
- Sharp dropoff of reflectivity above melting level reaching to just below 10 km
- Looks more like an eyewall CFAD

- 2008 TRMM Conference

- February 5th, 2008

## Eyewall

- Relatively narrow but intense distribution below melting level
- Weak brightband signature
- Mostly narrow distribution above melting level
- Outliers suggest occasional intense convective towers reaching over 12 km

- 2008 TRMM Conference

- February 5th, 2008

## Initial Conclusions

- Outer region has distinct ordinary convective signature with some stratiform
- Middle region rainbands have structure more similar to eyewall than to ordinary convection
- Eyewall CFAD is not like that of classic stratiform or convective precipitation- it is intense, deep, AND uniform
- Eyewall has intermittent deep convective elements
- No distinctive quadrant asymmetry, but will further test with larger dataset

- 2008 TRMM Conference

- February 5th, 2008

## Further Data

- First expansion is into the overpasses of all hurricanes between 1997-2007 that reach Category 4 and 5 intensity
- Overpasses are stratified into when the storm is Cat 1 or 2 and when Cat 3, 4, and 5
- Category 5 overpasses are also looked at separately

- 2008 TRMM Conference

- February 5th, 2008

## Slide 11

- 2008 TRMM Conference

- February 5th, 2008

## Further Data

- Generally consistent with the four 2005 storms, but differences between annuli are less when weaker storms are included.
- Eyewall distribution is broader when weaker storms are included

**Annulus 1**

**Annulus 3**

**Annulus 5**

- 2008 TRMM Conference

- February 5th, 2008

## Future work

- Continue expansion of database to all Atlantic Basin hurricanes, and eventually to all basins
- Stratify overpasses based on track speed, wind shear, and other factors known to influence storm structure and intensity
- Develop method of quantitatively sorting CFADs

- 2008 TRMM Conference

- February 5th, 2008