# Presentation: 007173

## SFMR Performance During the 2005  Hurricane Season

**Peter G. Black and Eric Uhlhorn**
**NOAA/AOML/Hurricane Research Division**
**Allan Goldstein, NOAA/AOC **
**Ivan Popstefanija, ProSensing. Inc. **
**and James Carswell, Remote Sensing Solutions, Inc.**
- 60th Interdepartmental Hurricane Conference
- Mobile, Alabama
- March 20-24, 2006

## 2005 SFMR Performance

**Flown in 9 storms, 7 **_**landfall situations**_
**Arlene****	**_**Cindy**_**	**_**Dennis**_
_**Emily**_**	****	****Irene****	****	**_**Katrina**_
_**Ophelia**_**	**_**Rita**_**	****	**_**Wilma**_
**34 total SFMR missions, 23 tasked**
**16 total, 8 tasked for NOAA42**
**18 total, 14 tasked for NOAA43**

## 2005 SFMR Performance (cont’d)

**SFMR used in 23 advisories, prompted 2 special advisories**
**All cases played decisive role in an important decision on current intensity or estimates of intensity change**
**Especially crucial for landfall intensity estimates for Dennis, Katrina, Rita and Wilma**
**Mentioned prominantly in Katrina, Rita and Ophelia NHC storm reports**

## SFMR Use Points to Key Deficit

**Difficult for forecasters to transition from routine AFRC flight level reco data to SFMR surface data, especially in landfall situations like Katrina**
**Extensive use of SFMR in 2004-2005 illustrates the urgent need for SFMR installation on WC-130J aircraft as soon as possible- especially critical in current era of enhanced TC activity**

## SFMR Updates

**From HRD projects:**
_**[http://www.aoml.noaa.gov/hrd/project2005/sfmr.html](http://www.aoml.noaa.gov/hrd/project2005/sfmr.html)**_
**From NHC storm reports:**
_**http://www.nhc.noaa.gov/2005atlan.shtml**_

## Key SFMR Issues

**Calibration vs. Model Development**
**Averaging Considerations**
**Real-Time Quality Control**
**Future Interpretation Issues**

## SFMR Calibration Procedure

**Single “pre-season” laboratory calibration by ProSensing**
**Single “pre-season” airborne ‘calibration adjustment’ of *****a*****0 ****for in-flight configuration**
**Flight in weak winds over known surface conditions (U10, SST) from redundant surface observation sources: buoy, GPS sonde, AXBT’s **
**Adjustment to theoretically-based *****T******B***
**In practice, should be performed annually**

## SFMR Model Development

**Empirically-based wind/emissivity (*****T******B*****) model function**
**Statistical correlation of surface wind estimates with calibrated SFMR measurements**
**Early model function related emissivity to surface adjusted flight-level winds**
**Since 2003, related to GPS sonde near-surface winds**
**Updated 2005 function based on larger data base of GPS near-surface winds**
**New model function corrects previously observed biases (e.g. moderate wind “high bias” & extreme wind “low bias” noted in 2004 data)**

## Slide 9

**Notes:**
A new wind/emissivity model was derived in 2005 from the extensive set of SFMR and dropwindsone observations in extreme CAT 4 and CAT5 conditions in Katrina and Rita. Together they formed a new relationship that is linear with wind speed above hurricane force, I.e. 33 m/s. This new relation further reduced high biases in moderate hurricane winds and low biases in extreme hurricane winds by 2-3 m/s, or about another 4%.

## Old

**Old**

**New**

**Corrects extreme wind**
**Low bias**

**Corrects moderate wind**
**High bias**

**Notes:**
A new wind/emissivity model was derived in 2005 from the extensive set of SFMR and dropwindsone observations in extreme CAT 4 and CAT5 conditions in Katrina and Rita. Together they formed a new relationship that is linear with wind speed above hurricane force, I.e. 33 m/s. This new relation further reduced high biases in moderate hurricane winds and low biases in extreme hurricane winds by 2-3 m/s, or about another 4%.

## New SFMR Wind/Emissivity Model Function

## Slide 12

**Notes:**
A new wind/emissivity model was derived in 2005 from the extensive set of SFMR and dropwindsone observations in extreme CAT 4 and CAT5 conditions in Katrina and Rita. Together they formed a new relationship that is linear with wind speed above hurricane force, I.e. 33 m/s. This new relation further reduced high biases in moderate hurricane winds and low biases in extreme hurricane winds by 2-3 m/s, or about another 4%.

## Slide 13

**Notes:**
A new wind/emissivity model was derived in 2005 from the extensive set of SFMR and dropwindsone observations in extreme CAT 4 and CAT5 conditions in Katrina and Rita. Together they formed a new relationship that is linear with wind speed above hurricane force, I.e. 33 m/s. This new relation further reduced high biases in moderate hurricane winds and low biases in extreme hurricane winds by 2-3 m/s, or about another 4%.

## Ocean Surface Whitecaps and Foam Streaks 

**200 m**
**Wind Speed ~ 46 m/s**

**200 m**
**Wind speed ~28m/s**

**Ocean Surface Whitecaps and Foam Streaks **
**in a Hurricane**

**Notes:**
The approximate field of view of the SFMR from 1500 m altitude showing the visual appearance of the foam and whitecap coverage change from 28-46 m/s. 

## SFMR measures C-band microwave emission from foam (air bubbles in the ocean)

**SFMR measures C-band microwave emission from foam (air bubbles in the ocean)**
**First guess pre-2005: Emissivity a quadratic function of wind speed for all winds.**
**2005 new knowledge:  Emissivity a quadratic function of wind up to hurricane force only- a linear function for hurricane winds**

**Notes:**
The SFMR is a new airborne remote sensing technology that measures sea surface emissivity at C-band. This quantity is direct measure of the concentration of bubbles in the ocean surface layer caused by wave breaking across the entire surface oceann wave spectrum. This quantity is shown to be a primarily a function of wind speed, based on more than 300 dropwindsonde obervations (Uhlhorn and Black, 2003) but is also dependent on surface roughness effects caused by wind/current interaction, anomalous wave breaking in shallow water and large sea surface temperature changes. 

This instrument therefore allows observations of surface wind speed to be made with an uncertainty of ±3-4 m/s, a nearly factor of two improvement over techniques used to estimate hurricane surface wind speeds over the ocean from flight level aircraft observations.

## Hurricane Katrina- SFMR 

**Hurricane Katrina- SFMR **
**29 Aug**
**Flat profile: Vmaxsfc=100 kt**
**28 Aug- Sharply peaked profile**
**Vmaxsfc= 142 kt**

**Red- SFMR sfc wind**
**Black- 700 mb flight level wind**
**Dot- Vmaxsfc NHC method**
**Diamond- Vmaxsfc Press/Wind**
**Square- GPS 10-m estimate**
**Triangle- GPS 10-m measurement**

**Open circle- 700 mb Gradient Wind**
**Blue dashed- Radial wind**

**Notes:**
SFMR observations from the 28th when Katrina achieved CAT5 status indicated close agreement between SFMR surface wind estimates of 138 kt, dropsonde peak wind estimates and surface winds estimated from standard flight level reduction from 3 km altitiude (142 kt). These methods also agreed with peak gradient wind estimates from flight level pressure measurements and with peak intensity estimated from standard pressure/wind nomograms. However, 10 hrs after these measurements, when Katrina made landfall, SFMR wind estimates showed a drastically lower surface wind (100 kt) than that estimated from flight level (still 136 kt- in rough agreement with the pressure/wind nomogram estimate). However, the SFMR measurements did agree with spot dropsonde measurements showing that SFMR observations were indeed valid. The problem arose because the SFMR ovservatons came in after the CAT4 intensity at landfall determination was made, they were seemingly unusually low. Additional passes were required to establish validity. 

## Averaging Considerations

**Model function**
**All SFMR channels update several times (~3s) over a 10s period**
**Correlate surface-adjusted WL150 wind speed (avg time = ??) with 10-s average SFMR (frequency-independent) emissivity**
**Cross-track footprint  (22 deg) vs along-track footprint for 10, 30, 60 s avg time @ 110 m/s (220 kt) GS:**
**RA =   330m (1500’):  0.2x1.3 km, 0.2x3.9 km, 0.2x7.8 km**
**RA = 1500m (5000’):  0.6x1.7 km, 0.6x5.1 km, 0.6x 10.2 km**
**RA = 3000m (10000’): 1.3x2.4 km, 1.3x7.2 km, 1.3x14.4 km**
**Reference: Swell wavelength ~ 200m; local sea ~ 75m**
**Issue: time required for air parcel at different wind speed to travel across one beamwidth on the surface**
**OR: time required for foam coverage to respond to changes in the wind**
**Consideration: since all waves from cm-scale capillaries up to the peak are likely breaking in hurricane conditions, time scale likely small~ minutes??**

## Averaging Considerations (Cont’d)

**Real time wind retrieval**
**Transmitted retrieval averaging tied to data rate in past**
**Need to be made consistent across all aircraft, i.e. IHC06 Agenda item proposal for 30-s average**

## Quality Control

**Basic QC checks**
**Outlier TB measurements**
**Aircraft pitch, rolls (> 6 deg)**
**Over-land measurements (Tb> 270K)**
**External QC**
**Landmasking**
**Bathymetry**
**Improved SST**
**NOAA flight director’s discretion (yes/no decision on data transmission)**
**Many issues are to be addressed by JHT**

## Other SFMR Issues (for SFMR JHT, YR 2)

**Bathymetry**
**SFMR issues in shallow water are still merely anecdotal, theory suggests that winds may be overestimated in ‘surf zone’ where swell breaking in shallow conditions**
**‘****Sheltered’ shallow water (offshore flow, Bahama Banks, Lake Ponchartrain) wind retrievals ‘look good’**
**To be addressed by excluding near-coastline “shallow-water” retrievals; extensive shallow-water dropsonde obs**
**Similar issue with wind/current interactions (no quantitative info), i.e. Gulf Stream, Loop Current boundaries**
**Rain**
**Has little effect on results at high (> 50 kt) winds, even in extreme rainrates (~ 50 mm/hr)**
**Weaker winds have tendency to be overestimated in heavy rain (e.g. in an outer rainband) – Issue is due to emissivity-rain model bias**

## WC-130J SFMR Installation Status

**Dec., 2004- $10.5M supplemental to DoD for SFMR on AFRC WC-130J’s**
**26 July, 2005- first Technical Interchange Meeting (TIM) at Wright-Paterson to define project scope- delivery of first SFMR set for Sept, 2006**
**Oct., 2005- Lockheed (LM) under contract**
**17 Nov., 2005- Second TIM at LM/Dobbins**
**Feb, 2006- Air Force purchasing office announces slippage in delivery to Jan, 2007**
**Mar, 2006- ProSensing under subcontract**
**Mar, 2006- With NOAA concurrence, G-IV SFMR to LM moves delivery to Nov, 2006**
**Mar, 2006- still no contract for delivery of remaining 9 SFMR units to operational WC-130J’s. **