# Presentation: 730075

## Tropical Cyclone Intensity Estimation Using

**Tropical Cyclone Intensity Estimation Using**
**Advanced Microwave Sounding Unit (AMSU) **

*Derrick Herndon*
*UW-Madison CIMSS*

*Mark DeMaria*
*NOAA/NESDIS/CIRA*

*Kurt F. Brueske, Major, USAF*
*United States Air Force Academy Department of Physics*

*Chris Velden*
*UW-Madison CIMSS*

*John Knaff*
*Colorado Institute for Research in the Atmosphere (CIRA)*

## Tropical Cyclone Intensity Estimation Using NOAA-KLM Series

**Tropical Cyclone Intensity Estimation Using NOAA-KLM Series**
**Advanced Microwave Sounding Unit (AMSU) **
**Warm Core Observations**

* **MSLP estimates derived from AMSU-A radiances*
*     **- Provides measure of upper level warm anomaly magnitude *
*     **- Channels 7 and 8 located at average ht of anomaly (150-250mb)*
*     **- Anomaly strength directly related to intensity*

***Hurricane Inez 1966***

***Hurricane Floyd 1999***

* **AMSU flown aboard NOAA 15, 16 and 17 as well as Aqua*
*     **- 6 estimates per day (2 more with Aqua)*

## CIRA AMSU Tropical Cyclone Algorithm

- V(r,

- Sample r/z tangential wind
- cross-section  from AMSU
- retrieval (steps 1-4)

- 1. Retrieve T(x,y,z) from all
-     AMSU-A channels
- 2. Correct T for rain and ice effects
- 3. Hydrostatic integration for P(x,y,z)
- 4. Gradient wind for V(r,z)
- 5. Statistical Prediction
-     _Independent Variables_:
-         Parameters from retrieved T, P, V
-     _Dependent Variables_:
-         Max Wind (Vmax)
-         Min Sea-Level Pressure (MSLP)
-         Azimuthally averaged radii
-              of 34, 50, 64 kt winds (r34, r50, r64)
- 6. Fit parametric wind model to r34, r50, r64
-     and storm speed to get asymmetric radii

**Notes:**
Summary of CIRA AMSU TC algorithm – Note that all AMSU channels are used and that the intensity and wind radii are estimated. The asymmetric radii are to the NE, SE, SW and NW of the storm center as required by the NHC forecast/advisory. 

## 2002 Real-Time Test  

- Algorithm developed from 1999-2001 Sample
- 2002 Real-Time Runs
- Initiated at 00, 06, 12, 18 UTC
- Storm positions from ATCF
- Analysis restricted to storms within 700 km of AMSU data swath
- Results sent to TPC via ftp
- Evaluation Samples
- 1999-2001 Developmental cases (N=473)
- 2002 All Atlantic/East Pacific cases (N=288)
- 2002 Atlantic/East Pacific cases with recon (N=64)
- Ground “Truth” for Evaluation
- NHC Best Track Vmax and MSLP
- NHC Forecast/Advisory for wind radii

**Notes:**
Summary of Real-time test during 2002 

## Predicted vs. “Observed” Scatter Plots for 2002 Real-Time Runs

**Predicted vs. “Observed” Scatter Plots for 2002 Real-Time Runs**
**(**_**Total**_** and **_**Recon-Only**_** Samples)**
** **

**Vmax**

**MSLP**

**R34**

**R50**

**R64**

**Notes:**
Main Points: 1) Relationships exist but with scatter. 2) Intensity plots have “quadratic” shape, because very intense storms are underestimated. 3) Wind radii relationship for R64 is not very good, but R34 and R50 are reasonable. 

## Error Summary for CIRA Algorithm:Developmental, 2002 All and 2002 Recon Samples

- <date/time>

**Error Summary for CIRA Algorithm:**_**Developmental**_**, **_**2002 All**_** and **_**2002 Recon**_** Samples**

**Absolute Error                               Variance Explained**

- Vmax
- and
- MSLP

- R34
- R50
- R64

**Vmax                   MSLP                                                                              Vmax                      MSLP**

**R34          R50           R64                                                                         R34           R50             R64**

**Notes:**
Main Points: 1) Little variation between three samples for Vmax and MSLP, which implies that the independent test reproduces what was expected from dependent data. 2) R34 and R50 characteristics similar for dependent/independent samples 3) Wind radii errors smaller for recon only sample 4) Not much variance explained for R64, but sample is small (N=8 for recon sample)

## CIMSS AMSU Tropical Cyclone Algorithm

**CIMSS AMSU Tropical Cyclone Algorithm**

* **Statistical Method Based on 1999-2001 regression against recon obs*
*     **- Linear fit (R****2****** ****= 0.82)*

*  **Independent estimates in 2002 comparable to Dvorak technique*

* **ATCF message provides RMW (Used as a proxy for anomaly size)*

* **Improved logic accounts for anomaly height, sub-sampling *

* **Channel 7 retrieval used to account for storms near limb*

- Resolution ~ 50km

## Compared to Dvorak (N= 60) in hPa

**2002 Results for Atlantic Basin**

- 		CIMSS	Dvorak
- Mean Error	  3.24		   4.52
- Std Dev	  2.29		   3.40
- Bias		 -0.28		  -0.90
- RMSE		  3.95		   5.62
- Avg MSLP of sample 1002.4

- Atlantic statistics for AMSU versus Recon (+/- 3 hrs) in hPa (N=63)
- Mean Error	  3.24		           Std Dev	  2.29
- Bias		 -0.42
- RMSE		  3.96
- Avg MSLP of sample 1002.6

## 2002 Atlantic Basin Results

**2002 Atlantic Basin Results**

- AMSU
- 81% within +/-  0.5T

- NOAA/NESDIS Satellite Analysis Branch (SAB)
- vs.
- AMSU
- (N=34, +/- 2hrs of aircraft reconnaissance)

- SAB
- 78% within +/- 0.5T

## Slide 10

## Future Work

## Summary

-  Penetrates cloud cover
-  55 Ghz region radiances can quantify inner core thermal
-    structure / changes.
-  Temperature anomaly strength directly associated with tropical
-    cyclone intensity
-  Skill comparable to, and in some cases better than, the Dvorak estimates
-  An important new addition to the forecaster “tool kit”

***AMSU provides unique tropical cyclone perspective******  ***

## Conclusions from 2002 Evaluation

- Vmax, MSLP (CIRA):
- 2002 (independent) performance very similar to (slightly improved) over dependent sample
- Intensity underestimated for small-cored systems
- Wind Radii (CIRA Method):
- 2002 recon-only errors generally similar to dependent sample
- Tendency for high bias for R50 and R64
- Observed  R50 and R64 more asymmetric than predicted

- Addition of second AMSU channel (CIMSS):
- Accounts for variability in TC temperature anomaly height
- Improvements resulting from advanced algorithm logic (CIMSS):
- Based on evaluation of 3 years of estimates, continues to evolve
- Additional improvements foreseen in 2003:
- Characterization and new regressions for small-cored storms

- JHT pathway in 2003:
- Continue evaluation of 2002 performance
- Implement algorithm upgrades and re-evaluate after 2003 season
- If successful and approved, activate improved algorithms at TPC

**Notes:**
Additional Comment: 1) TPC will perform their own evaluation (Jack Beven) 2) TPC will also compare CIRA, CIMSS and NASA (Roy Spencer) results for homogeneous sample