# Presentation: 935822

## The Operational Impact of and Future Requirements for Satellite Ocean Surface Vector Winds in Tropical Cyclone Analysis

**The Operational Impact of and Future Requirements for Satellite Ocean Surface Vector Winds in Tropical Cyclone Analysis**

- Michael Brennan1, Richard Knabb1, Paul Chang2, Joseph Sienkiewicz3, Zorana Jelenak2, Kevin Schrab4
- 1NOAA/NWS/NCEP/NHC, 2NOAA/NESDIS/STAR, 3NOAA/NWS/NCEP/OPC, 4NOAA/NWS/OST
- 61st Interdepartmental Hurricane Conference
- 6 March 2007

## Impact of OSVW Data on TC Analysis and Forecasting 

- QuikSCAT data available in operational workstations at NHC since 2000
- Some information on TC intensity, especially for tropical storms, but not major hurricanes
- Limited by instrument resolution
- Interpretation complicated by rain contamination
- Improved detection/tracking of TC centers for analysis and model initialization
- Often only source of outer wind radii information for open ocean systems  affects watch/warning areas

## Use of QuikSCAT at NHC 

- Based on 2003–2006 Tropical Cyclone Discussions

- Does not account for instances where QSCAT used but not explicitly mentioned in TCD

**Notes:**
The trend is definitely upward in the Atlantic, increasing from 5% to over 20% since 2000.  The East Pacific percentage has remained between 15% and 20% since 2001.  The higher percentage initially in the East Pacific is likely due to the relative lack of aircraft reconnaissance information in that basin compared to the Atlantic, as forecasters rely on remotely sensed data more heavily in the East Pacific.
These percentages are actually quite high if you consider that with at most two passes a day over a TC, at best only 2 of the 4 routine daily TCDs are being written by a forecaster who has new QuikSCAT data to look at (in reality its even lower than that due to TCs missed in the gaps between QuikSCAT swaths).  These percentages could be doubled to give a rough estimate of the frequency at which QuikSCAT data is mentioned mentions per opportunity to do so.  Doing so results in QuikSCAT data now being mentioned in ~ 40% of TCDs when there is new data available.  By comparison, TRMM is mentioned in ~ 4% of TCDs. 

A related point one could quickly make is that our understanding of how to interpret QuikSCAT data in TCs has also been increasing during the same period.  And to be honest, that learning process is still ongoing, because the several limitations and pitfalls of the instrument in TC environments require such careful analysis, and many of our forecasters still need more training.  Several of the references to QuikSCAT in our discussions could easily be taken to task for misinterpretation, esp. the farther back in time you go.  I just don't want anyone to conclude that increased use means we've figured out how to confidently get unambiguous answers from the data.  I'd rather they conclude that we've been doing our best to squeeze every last bit of operationally useful information from a research instrument that is really not designed for use in TCs. 

## NOAA OSVW Requirements Workshop5–7 June 2006 – NHC, Miami, FL 

- Goals
- Summarize utility and impact of currently available satellite OSVW data in operational weather forecasting
- Define NOAA’s operational OSVW requirements
- Explore sensor/mission concepts using proven remote sensing technologies to meet these requirements

**Notes:**
Near-real-time measurements of ocean surface vector winds (OSVW) including both wind speed and direction from non-NOAA research satellites are being widely used in critical operational NOAA forecasting and warning activities.  Wind observations in near all-weather conditions from the NASA QuikSCAT mission (launched in June 1999) have been incorporated into daily operations at NOAA’s Ocean Prediction Center (OPC) and Tropical Prediction Center/ National Hurricane Center (TPC/NHC) since 2000. QuikSCAT data have been assimilated routinely for numerical weather prediction modeling at the National Centers for Environmental Prediction (NCEP) as well as numerous international weather centers such as the European Center for Medium-Range Weather Forecasting (ECMWF) since January 15, 2002. 
Workshop held in TPC center in June this year aimed to:
-Document the operational utilization and impact of satellite surface wind speed and direction measurements; and 
-Consider measurement accuracy, resolution, and coverage requirements for future NOAA operational ocean vector wind products in light of present experience from research missions, and planned future advances in the areas of numerical weather models, analytical techniques, and NOAA global, regional, and storm warning and forecast requirements 

## Who Else is Using OSVW?Workshop Participants

- NHC, CPHC, JTWC
- TC analysis and forecasting
- NWS Ocean Prediction Center, NHC’s Tropical Analysis and Forecast Branch (TAFB), NWS coastal WFOs, DoD
- Marine forecasts, warnings, and analyses
- Identification of hurricane force extratropical cyclones at OPC
- NOAA/NESDIS – Develop retrieval algorithms, data processing, real time data distribution
- NCEP/Environmental Modeling Center, FNMOC, ECMWF
- Data assimilation for NWP modeling
- NASA/JPL
- Academic and research communities
- Private sector marine forecasters, recreational mariners

**Notes:**
This also feeds into the following larger platforms that are priorities for NOAA:
 GEOSS (Global Earth Observing System of Systems)
 IOOS (Integrated Ocean Observing System)
 US Ocean Action Plan

And it is conceivable that many other NOAA units like Commerce and Transportation, Fisheries, NMAO, and Coastal Services would find this data useful.

## Operational Requirements

**Operational Requirements**

**All-weather retrievals**
**Accurate retrievals in rain**
- Accuracy levied upon 10-m 1-min sustained wind
- Speed: +/- 2 kt in 0–165 kt wind range
- Direction:
- +/- 10° (2 σ) (10–165 kt)
- +/- 20° (2 σ) (4–10 kt)
- Revisit time: 6 h (1–3 h goal)
- Interval between measurements at particular point on ocean surface

- Helene 23 September 2006

**Notes:**
The operational needs and experience with the currently available satellite OSVW 
measurements presented during the workshop culminated in the formulation of
new operational OSVW requirements.  These requirements reflect the observational
 needs of NWS and JTWC forecasters to prepare warnings and forecasts for a variety
 of meteorological and oceanographic phenomena observed over the oceans including: 
tropical cyclones, extratropical ocean storms, areas of convection, gap flows, upwelling 
areas, topographically induced or enhanced jets, and island and mountain wakes.  
The spatial grid spacing reflects both the phenomena observed and the horizontal 
resolution of gridded forecasts now produced in operations by coastal NWS 
Weather Forecast Offices.

## Operational Requirements

- Reduce time from measurement to product availability (product latency) to 45–60 min
- 15 min goal
- 2.5 km x 2.5 km spacing between unique wind vector retrievals (1 km goal)
- Retrievals within 2.5 km** **of coast (1 km goal)
- Data delivered into operational workstations (N-AWIPS/AWIPS) and data assimilation systems
- Product documentation/tutorials/training

**Notes:**
The operational needs and experience with the currently available satellite OSVW 
measurements presented during the workshop culminated in the formulation of
new operational OSVW requirements.  These requirements reflect the observational
 needs of NWS and JTWC forecasters to prepare warnings and forecasts for a variety
 of meteorological and oceanographic phenomena observed over the oceans including: 
tropical cyclones, extratropical ocean storms, areas of convection, gap flows, upwelling 
areas, topographically induced or enhanced jets, and island and mountain wakes.  
The spatial grid spacing reflects both the phenomena observed and the horizontal 
resolution of gridded forecasts now produced in operations by coastal NWS 
Weather Forecast Offices.

## Instrument Resolution Affects Ability to Measure Maximum Wind (Max retrievable wind speed does not account for rain effects)

**Instrument Resolution Affects Ability to Measure Maximum Wind ****(Max retrievable wind speed does not account for rain effects)**

**Notes:**
First panel on the slide (top left one) represents surface wind field with resolution of 1km obtained from true wind field. True meaning this was no hypothetical situation but the field was derived from a something that really existed.. That first plot clearly shows small scale features visible when 1km resolution is available. 

Subsequent plots are showing how those features are diminishing when resolution of the measurements is degraded. The low resolution plots were not just created as the average of the true plot since something like that would not be achievable with the true sensor. The actual low resolution plots were obtained by interpolating the measurements rather then smoothing them. 
Three bottom resolutions were selected based on CMIS replacement sensor proposals that we had at the time of MOAT briefing. Comparison of those with third one on the top panel clearly shows the degradation in the data quality and warning impact that future planned instrument will bring.
These are theoretical limits – real world problems, like rain contamination, would not allow one to reach max wind speeds

## Current and Future OSVW Missions

**Current and Future OSVW Missions**

**AMI/ERS-2**

**     ****Seawinds/QuikSCAT**

**WINDSAT**

**97**

**98**

**99**

**00**

**01**

**02**

**03**

**04**

**05**

**06**

**07**

**08**

**09**

**10**

**11**

**12**

**13**

**14**

**15**

**In ****orbit**

**Approved**

** ****Planned foreign missions**
** ****Unknown instrument designs**
** ****Research missions**
** ****Questionable data availability (no agreements in place to share data)**

**SeaWINDS/ADEOS-II**

**895 km**

**1700 km**

**500 km**

**1600 km**

**2 x 550 km w/ 768-km nadir gap**
**~60% of QuikSCAT coverage**

**X**

**No CMIS on NPOESS C-1**
**A less capable CMIS-successor is planned beginning with C-2 in 2016.**

- ?

**ASCAT/METOP – 3-satellite series**

**Notes:**
ERS-2:  The on-board recording no longer functions so observations can only be made available via real-time direct reception, should ESA decide to exercise that option.
QuikSCAT:  Launched in 1999, earlier this month it completed 7 years of operation, and it is now starting its 8th year. The satellite, instrument and ground system continue to function well and are meeting mission requirements.  Aging of the scatterometer antenna bearings is the highest mission risk; friction in the bearings fluctuates, but continues to return to nominal “comfort zone” levels; margin remains on the motor torque capacity; spin rate is not effected.
WindSat:  Launched in early 2003, WindSat continues to perform as planned.  Earlier this year the full mission data set was made available for evaluation by the community at large.  
ASCAT/METOP:  A C-band scatterometer, building on the ERS heritage, will be flown on each of three METOP satellites, the first planned for launch next month.  Coverage will feature two 550-km swaths with a 768-km nadir gap – approximately 70% of that for QuikSCAT.  
CMIS/NPOESS:  CMIS was cancelled as a result of the Nunn-McCurdy process, and there will be no capability for passive polarimetry on NPOESS C-1.  A CMIS-like instrument is to be developed for flight on C-2, planned for launch in 2016. 
Oceansat-2 – Indian Ku-band scatterometer, launch planned for 2007, instrument not build yet, no details about instrument available, no agreements to get data 
HY-2 – Chinese scatterometer. Not approved yet, if approved launch planned for 2009. No design detail available no data agreements

## Next Generation Ocean Vector Wind Mission (XOVWM)

- Recommended to NOAA by National Academies’ *Decadal Survey*
- XOVWM combines available technology and measurement heritage  represents order of magnitude **advance** in scientific and operational capability with moderate risk and cost
- Ku-band scatterometer (high resolution)
- C-band scatterometer (less sensitivity to rain)
- Multi-frequency polarimetric radiometer (provide rain corrections)
- Meeting revisit time requirements (6 h) would require at least 2, and probably 3 satellites

## Key Recommendations

*Interagency Strategic Research Plan for Tropical Cyclones: The Way Ahead*, February 2007
- “Due to the **importance of OSVW data**—for use by tropical cyclone forecasters and in tropical cyclone NWP systems—the JAG/TCR **strongly endorses** the development and acquisition of a capability to** meet the OSVW observation requirements**. This capability is **absolutely critical to meeting the operational needs of the tropical cyclone forecast and warning centers**...”
- Sixth WMO International Workshop on Tropical Cyclones (IWTC-VI), San José, Costa Rica, 21-30 November 2006
- “IWTC-VI recommends that the WMO Space Program **strongly endorse** the specific recommendations of the US National Oceanic and Atmospheric Administration **Operational Satellite Ocean Surface Wind Vector Winds Requirements Workshop Report**....”
*Majority Report*, NOAA Science Advisory Board Hurricane Intensity Research Working Group, 8 October 2006
- “Combining a broad range of atmospheric and oceanic observing techniques provides the best overall observing capacity. The **current mix of satellites,** manned aircraft, buoys, radar, etc, **should be maintained as a critical component of the overall hurricane forecasting process**.”

## Summary

- Currently available operational OSVW data have led to significant improvements in TC analysis and forecasting
- Advances in marine analyses, forecasts, and warnings from high seas to coastal waters
- NOAA has no plans to launch an operational OSVW mission to maintain current data quality after QuikSCAT
- Cannot afford take step backward and lose improvements made!
- High-quality OSVW data critical to addressing hurricane intensity problem
- Analysis tool for inner core structure for model input and validation of model output

## Summary

- OSVW data from NPOESS MIS likely of limited utility for TC analysis
- Based on experience with WindSat at NHC
- Resolution not sufficient for TC analysis needs, maybe no wind direction?
- Future international research missions
- Availability and quality of data unknown
- Place XOVWM on accelerated timetable
- Minimize post-QuikSCAT gap in high-quality OSVW data
- Some of cost could be defrayed by limiting the ocean vector winds capabilities of MIS

## Goals for Continued use of OSVW Data in Operations

**Short term**
- Push QuikSCAT capabilities to limits
- Attempt to improve WindSat retrievals
- Expedite data processing, distribution, and training for ASCAT
**Mid Term**
- Maintain operational availability of QuikSCAT data through instrument life span beyond FY09
- FY09 – Study and design of XOVWM mission (sensor, satellite bus and ground system)
**Long Term**
- FY10–12 – procurement, integration, and testing of XOVWM
- FY13 – XOVWM mission launch and calibration/validation

- ASCAT Coverage (courtesy COMET/EUMETSAT)

- QuikSCAT launch (courtesy NASA)

## Activity since NOAA Workshop

- July 2006
- Attended NASA Ocean Vector Winds Science Team meeting
- August 2006
- Workshop report finalized and distributed
- September 2006
- Briefed the Technical Director for the Oceanographer of the Navy
- October 2006
- Briefed NWS Director Johnson
- Attended NPOESS Polar Max meeting
- November 2006
- Briefed NOAA CFO and Program Analysis and Evaluation Director
- December 2006
- Presentations given at AGU Fall Meeting and NOAA Hurricane Conference
- Interactions with NASA about next generation OSVW mission
- January 2007
- Briefed Vice Admiral Lautenbacher
- Presentation given at AMS Annual Meeting
- February 2007
- Briefed NOAA Observing Systems Council

## Feedback from DoD

- DoD support for XOVWM would bolster efforts to move toward NOAA’s operational requirements and limit post-QuikSCAT data gap
- Reference IHC Action Item #2: “Satellite Ocean Surface Vector Winds Operational Impacts and Requirements” – Thursday
- Informal meeting in the hall after this session

## Additional Slides

## ASCAT Coverage

- QuikSCAT pass over Katrina

##  WindSat in TCs – Preliminary Evaluation

- WindSat not able to retrieve hurricane force winds in raining conditions with current algorithm
- Limited by ~50 km resolution
- Current wind vector solution not suitable for TC center fixing
- Difficultly closing off circulations – broad wind shift often seen instead of well-defined center
- 37GHz imagery better suited, other frequencies and polarizations being evaluated

## Other Future OSVW Missions

**NPOESS **
- Conical Microwave Imager/Sounder (CMIS) cancelled
- Replacement passive instrument (MIS) being reconfigured
- 1.2–1.8 m dish size will limit resolution
- Resolution similar to or worse than WindSat (50 km)
- Wind direction may be tradable quantity
- Earliest MIS will fly is 2016 on NPOESS/C2
**India/China**** **
- Each planning scatterometry mission
- Design uncertain
- No agreement to share data

## ASCAT

- Courtesy EUMETSAT

## Comparison of IORD II requirements and QuikSCAT 

**and WindSat performance**

|  |  | 
IORD-II
Threshold | QuikSCAT |  | WindSat | IORD-II
Objective | NEW SVW Requirements |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Horizontal Cell Size |  | 20km | 25km | 12km | 50km operational | 1km | 2.5km x2.5km unique grid spacing
1kmx1km goal |
|  |  |  | operational |  |  |  |  |
|  |  |  | 5km experimental |  | 35km experimental |  |  |
| Mapping Uncertainty |  | 5km |  |  |  | 1km |  |
| Measurement Range |  | 6-50kts
0-360° | 6-75kts
0-360o |  | 6-50kts
0-360o | 6-95kts
0-360o | 0-165kts
0-360o |
| Measurement Accuracy | Speed | Greater of  4kts or 10% | ~2.3kts |  | ~2.3kts | Greater of 1.9kts or 10% | All wspd      +/-1.9kts |
|  | Direction | Wspd>10kts ~20o | Wspd<6kts >20o  |  | Wspd>15kts <20o | ~10o | wspd >10kts  ~10o |
|  |  | Wspd<10kts ~ 25o | Wspd >6kts <20o |  | Wspd<15kts <30o | ~10o | Wspd<10kts ~20o |
| Latency |  | 90min | 3h |  | 5h | 15min | 45-60min
15min goal |
| Revisit Time |  | 6h | 18h |  | 34h | 1h | 6h (1-3h goal) |
| Swath Width |  | 1700km | 1800km |  | 1000km |  |  |
| Coastal Winds |  |  | 30/20km of the coast |  | 75km of the coast |  | 2.5km of the coast |
|  |  |  |  |  |  |  |  |

**Notes:**
QuikSCAT exceeds IORD-II thresholds; WindSat does not
New OSVW requirements equal or exceed IORD-II objectives

Yellow-IORD threshold accuracies that future NPOESS OSVW instrument should satisfy
Red-measurements available today that are bellow IORD threshold
Green-measurements available today performs above IORD threshold

## OSVW Measurements Currently AvailableProvided by NASA QuikSCAT

- Accuracy of ocean surface wind speed and direction
- Speed: ~2 kt from 6 – 75 kt
- Direction: ~ 20° for winds > 6 kt
- Operational 25-km and 12.5-km retrievals
- Retrievals within 20 km of coast
- 1800-km wide measurement swath
- ~ 3 h from data measurement to display on operational workstations
- ~18 h between measurements at a given point on the ocean surface
- Time between measurements over a TC can be much longer due to wide swath gaps at low latitudes

## WindSat

- Launched on Coriolis satellite January 2003 – retrievals available at NHC since June 2006
- 900-km wide data swath
- ~50-km resolution of wind retrievals
- First attempt to retrieve ***wind vector*** with passive sensor
- Unable to retrieve hurricane force winds in raining conditions with current algorithm
- Current wind vector solution not suitable for TC center fixing

## QuikSCAT

- Ku-band scatterometer
- Designed for 5-yr life span, now in 8th year
- On backup transmitter (primary failed July 2006)
- Orbit maneuvers not necessary through 2009
- Instrument healthy and should continue to operate for several more years
- NASA funding data acquisition/processing through 2009

## Other Current OSVW Instruments

**WindSat Passive Radiometer**
- Launched January 2003 as risk reduction mission for NPOESS CMIS
- First attempt to retrieve ***wind vector*** with passive sensor
- 50-km resolution wind retrievals
- Unable to retrieve hurricane force winds in raining conditions with current algorithm
- Wind vector solution not suitable for TC center fixing based on NHC evaluation
**ASCAT Scatterometer**
- Onboard METOP-A satellite launched 19 October 2006
- C-band scatterometer - less sensitive to rain
- Coverage ~ 60% of QuikSCAT
- 2 parallel 550-km swaths
- 720-km nadir gap
- Operational retrievals expected later this year
- 50 km resolution
- 25 km retrievals by end of 2008
- Onboard METOP-B and METOP-C scheduled for launch every 4.5 years