# Presentation: 030823

## Examination of the tropical cyclone environmentthrough comparison of COSMICwith other satellite data

- Christopher M. Hill, Patrick J. Fitzpatrick, and Yee Lau
- Geosystems Research Institute / Northern Gulf Institute
- Mississippi State University
- March 3, 2009
- 63rd Interdepartmental Hurricane Conference

## Motivation to use COSMIC

- in the absence of reconnaissance flights or other satellite data
- in cloudy or rain-filled regions, where other satellite data are contaminated
- Regions or layers of contrasting moisture content can be identified within:
-  the span and depth of a Saharan Air Layer (SAL)
-  the core of a tropical cyclone

## Motivation to use COSMIC

- Given ***N*****(*****p*****)**, it is possible to solve for ***T*** and/or ***e*** (and therefore ***T******d***)

- [dry term]        [wet term]

- According to Ware et al. (1996), the error of ***e*** in terms of the error of ***T*** is:
-    With ***N*** and ***p*** known,
- a value of ***T ***known within ± 3 K can typically provide
- a value of ***e*** within ± 1 hPa

## Methodology

- Within the environment of the tropics, where temperature differences are small, the analysis of refractivity (***N***) alone can provide useful information regarding the distribution of moisture within one of the profiles
- COSMIC data are collected in the vicinity of recent tropical cyclones
- Helene 2006, Dean 2007, Bertha 2008
- Based on water vapor imagery and METEOSAT SAL (12.0 *μ*m minus 10.8 *μ*m) imagery, likely “dry” and “moist” profiles are qualitatively identified and differenced
- To detect SALs, COSMIC refractivity data are compared against CALIPSO aerosol subtype data

## Differences of COSMIC refractivity between

- SAL and non-SAL columns
- (approx. 00 UTC 16 Sept 2006)

- SAL column point
- non-SAL column point

- COSMIC  retrieved dewpoint (°C)

- COSMIC refractivity

- Non-SAL minus SAL refractivity

**METEOSAT-8 SAL imagery provided by CIMSS / SSEC / Univ. of WI**

**Helene**

**Difference of 41**
**at 3.2 km**

## COSMIC and CALIPSO data near Dean 200717 Aug 2007

- COSMIC and CALIPSO data near Dean 200717 Aug 2007

**Difference of  20**
**at 4.8 km**

- COSMIC refractivity difference [ C1 – C2 ]
- Retrieved ***T******d***  difference [ C1 – C2 ]
**~ 04:30 UTC 17 Aug 2007**

- GOES-12 imagery provided by NCDC       03 UTC 17 August 2007

- COSMIC #1
- COSMIC #2

- CALIPSO

- COSMIC point  #1:  29.0°N  50.6°W
- COSMIC point  #2:  20.3°N  51.9°W

- Influence of   Δ***T  *****?**

**NASA**

## Methodology

- COSMIC data are found within the circulation area of recent tropical cyclones
- STY Sepat 2007,  Bertha and Ike 2008
- 4th-order polynomial curve fitted against COSMIC profile
- difference between profile and fitted curve should show refractivity (moisture) anomalies
- COSMIC data are compared against water vapor and microwave imagery to determine cyclone structure

- COSMIC profile
- 4th-order polynomial

## COSMIC and CALIPSO data near Bertha 200808 July 2008

- Difference of COSMIC refractivity profile and 4th-order fitted curve
**14:19 UTC  08 July 2008**

- est. radius of max. wind

- intersection  heights

**NASA**

## COSMIC and CALIPSO data near Bertha 200808 July 2008

- COSMIC and CALIPSO data near Bertha 200808 July 2008

- Difference of COSMIC refractivity profile and 4th-order fitted curve
**14:19 UTC  08 July 2008**

**E  Eyewall ?**

**Eye ?**
**   **[

**rainbands?**

- est. radius of max. wind

- intersection  heights

**S  Eyewall ?**

## [

- 06 UTC   06 Sept

**NHC**

- COSMIC analysis of Hurricane Ike 2008

**NOAA-18**
**AMSU-B  06:23 UTC 06 Sept 2008**

**NRL**

**05:25 UTC**

- est. radius of max. wind

**Rainbands?**

** ****dry air**

**GOES-12**
**WV  06:45 UTC 06 Sept 2008**

**Refractivity Difference**
**profile  minus  4****th****-order fitted curve**

## Eyewall replacement cycle with Supertyphoon Sepat   08/16/2007

- microwave imagery archived at the Naval Research Laboratory

## COSMIC analysis of Supertyphoon Sepat  2007

- COSMIC profile relative to _**estimations**_ of the storm center and the radii of concentric eyes

**06:05 UTC**

**AMSU-B   08:44 UTC  16 Aug 2007**

**NRL**

**Inner**
**Eyewall??**

**Outer Eye ??**

**SW  Outer Eyewall ??**

**Refractivity Difference**
**profile  minus  4****th****-order fitted curve**

**Outer Eye ??**

## Some conclusions on use of COSMIC near tropical cyclones

- Difference of COSMIC refractivity can show dry air signature of SAL
- Combined use of COSMIC and CALIPSO can definitively show SAL
- COSMIC can detect inner core features of a cyclone hidden under the cirrus canopy  (precise matching with other data is crucial !)
- COSMIC may help to determine the stage of eyewall replacement cycle

**Acknowledgments**
- The organization of COSMIC for the COSMIC profile data
- CIMSS / SSEC / Univ. of WI,  NRL,  NCDC, and NASA for satellite data
- Dr. Eric Hendricks for a helpful poster discussion