# Presentation: 051957

## QuikSCAT Follow-On Options:Wind Vector Retrievals  Simulation Study ResultsSimulations performed at JPL and provided to NOAA for user analyses and validationSpecial thanks to JPL team Ernesto Rodriguez, Rob Gaston, Scott Dunbar, Svetla Velva, Brian Stiles, Daniel Esteban-Fernandez, Samuel Chan

**Zorana Jelenak **
**NOAA/NESDIS/StAR-UCAR**

## Foreseen Impact on NOAA Operations

**Higher spatial resolution (~5km)**
**Full wind speed range (to category 5), **
**Coastal coverage 2.5-5 km of land**
**Significantly better retrievals in rain impacted measurements**
**Areas of Emphasis:**
- Tropical cyclones (Katrina (4) and Rita (5))
- Extra-tropical cyclones (Helene, Seattle storm Dec 2006)
- Coastal winds (dual low level jets off of Cape Blanco and Cape Mendocino, high wind events along the  Alaska coast )

**Notes:**
XOVWM mission would advance capabilities closer to the NOAA OSVW requirements for operational weather forecasting and warning documented at the NOAA OSVW workshop held at the National Hurricane Center in June 2006. There are several areas where next-generation scatterometer will have advances over a  QuikSCAT-like mission. Those are:
Higher resolution measurements (~5-3km vs 12.5km)
Measurements closer to the coast (~5km vs 30km)
Measurements in rain
Measurements of high wind events (up to 80m/s vs 40m/s)
To achieve the study goals we investigated the differences in performance between two mission options in hurricanes, extra-tropical storms and coastal wind jet events. 

## WRF Simulations

**Initial/boundary conditions from **
**the GFDL 1/6****th**** degree and 1deg resolution NCEP m**
**A set of three nested grids were used**
**outer most grid with a resolution of 12 km and covering ~5000x5000km**
**the middle grid with a resolution of 4km **
**inner most grid with a resolution of 1.3km and covering ~500x500km.  **
**Used was a 6-class microphysical scheme (vapor, cloud liquid, rain, cloud ice, snow and graupel).  This is one of the most complex from the currently available schemes. **

**Notes:**
To obtain realistic wind and corresponding atmospheric field in hurricanes WRF model and Cloud resolving mode was run for Katrina, Rita nad Helene examples. Simulations were done by Svetla Velva (JPL). WRF is a state-of-the-art meteorological model being developed collaboratively among several agencies (NOAA/NCEP, NOAA/FSL, NCAR) and designed to study mesoscale and convective scale processes. WRF can be run with multiple nested grids with different spatial resolution to allow resolving both the highly 3D structure of convection and the extensive mesoscale circulations. We used the following setup when simulating Katrina and Rita: In both cases we used a set of three nested grids with the outer most grid having a resolution of 12 km and covering ~5000x5000km, the middle having a resolution of 4km and the most inner one having a resolution of 1.3km and covering ~500x500km.  The runs were designed such that the inner two grids were moving, following the motion of the vortex center.  The high resolution of the most inner grid assures the proper representation of the processes in the hurricane eyewall  a region that plays a critical role in the storm development. 
It can be run in a number of different modes, one of which is the cloud-resolving mode (model). In the case of Katrina, the initial/boundary conditions were provided by
1deg resolution NCEP model run while in the case of Rita the GFDL 1/6th degree model run was used. The WRF output fields used in the scatterometer simulator were the following: the 10 m wind; the 3D precipitation structure (at a stretched vertical grid with 30 model levels).  The 3D precipitation structure in the lowest 15 km was then interpolated to 30 vertical levels with 500m vertical resolution.  This precipitation structure was then used to simulate the attenuation (produced by precipitation, cloud and vapor) and the volume backscatter (produced by the precipitation).  Mie scattering code was used to compute the attenuation and the volume backscatter at the frequencies and the polarization of the XOVWM instrument.  Furthermore, an incidence angle correction was made in the path of the scattrometer signal through the precipitation.

## Slide 4

**Notes:**
Scatterometers are microwave radar instruments specifically designed to measure near surface ocean wind speed and direction under all whether conditions. The scattermoter emits microwave pulses that scatters off the ocean surface. Scattering occurs in all directions but scatterometers measure only part of the signal backscattered in the same direction as incoming radiation. The quantity measured by scatterometers is called normalized radar cross-section (sigma0) and is proportional to the ratio of reflected power to transmitted power.  Changes in near surface wind field change scatterometer return power therefore modify sigma0 values. For simulation purposes we have opposite problem to model: Using known transmitted power and known surface wind and corresponding atmospheric conditions calculate measured sigma0’s. 
For known transmitted power and known ocean surface wind conditions and corresponding atmosphere model of measured sigma0’s is required

## Simulating Scatterometer Measurements

**Simulating Scatterometer Measurements**

**Ku-band V, H pol**

**C-band V, H pol**

**Ku-band V, H pol**

- Simultaneous rain and wind retrievals – rain rate information not available

- Wind retrievals

**Notes:**
Using WRF output model simulations were run to obtain Ku-band measurements at two polarizations to simulate QuikSCAT like measurements and to obtain C-band and Ku-band measurements of XOVWM instrument. After estimating sigma0 measurements using WRF model outputs for surface and atmospheric conditions retrievals of ocean surface wind fields were run providing winds at 12.5km resolution for QuikSCAT-like instrument and at 5km for XOVWM. 
Geophysical model function (GMF) relates measured sigma0 to surface parameters (wind speed and direction) and scatterometer parameters (incidence angle, azimuth angle, polarization and frequency). For this exercise GMF used was high wind model function developed from IWRAP measurements (Daniel Esteban-Fernandez) on board of NOAA P3 aircraft. IWRAP high wind model functions show that only C-band H-pol measurement doesn’t saturate as wind speed increases

## Katrina – 3rd Example  8/28/2005-23:50

**Katrina – 3****rd**** Example  8/28/2005-23:50**

**Notes:**
Following Katrina hurricane on 28th and 29th of August we have run 4 measurement and retrieval simulation for QuikSCAT-like and next generation sensor.
To plots show WRF’s output for rain rate and surface wind field on 8/28 at 23:50UTC. The areas of highest rain are marked with white line. Model winds show very little variation of wind speed in that region 

## Katrina – 3rd Example  8/28/2005-23:50

**Katrina – 3****rd**** Example  8/28/2005-23:50**

**Notes:**
WRF model surface wind and corresponding QuikSCAT-like wind vector retrievals. It is interesting to note that in area of highest rain (marked with white line) QuikSCAT-like retrieved wind speed has high gradient going all the way from 80kths (27N 89.7W) to 42kts (27.2N 89.3W). While size of the storm is estimated right the area oh highest winds is much smaller and storm structure seems distorted

## Katrina – 3rd Example  8/28/2005-23:50

**Katrina – 3****rd**** Example  8/28/2005-23:50**

**Notes:**
WRF model surface wind and corresponding XOVWM wind vector retrievals. Storm structure seems to be retrieved properly. Simultaneous rain and wind retrievals helped surface retrievals within area of highest rain (encircled by white line). Note subtstantional difference between QuikSCAT-like and XOVWM retrievals.

## Katrina – 4th Example 8/29/2005 -5:50

**Katrina – 4****th**** Example 8/29/2005 -5:50**

**Notes:**
WRF wind field and rain rate output for katrina Hurricane on 8/29/05 at 5.50UTC.

## Katrina – 4th Example  8/29/2005-5:50

**Katrina – 4th Example  8/29/2005-5:50**

**Notes:**
WRF surface wind field and corresponding QuikSCAT-like surface retrievals. QS shows only a broad wind minimum where the tight eyewall wind gradient is actually present. The QS "circulation center" is elongated NW-SE and actually according to the directional vectors shows a center a full 60 NM southeast of the WRF depiction

## Katrina – 4th Example  8/29/2005-5:50

**Katrina – 4th Example  8/29/2005-5:50**

**Notes:**
WRF surface wind field and corresponding XOVWM-retrievals. Its clearly obvious that the XOVWM retrievals depict all facets of the TC wind field more accurately than QS, from the maximum winds to the inner and outer wind field structure. The impacts of rain contamination are clearly visible in the QS retrievals, particularly in isolated wind maxima in rainbands. These features are not evident in the XOVWM retrievals, which show much less sensitivity to the rain field produced by the WRF simulation. The impact of the increased resolution of the XOVWM retrievals are seen in the better resolution of the wind minimum in Katrina's eye and of stronger winds in the eyewall. Additionally, the directional retrievals near the center from XOWVM are much more realistic looking and better define the center than those from QS
The WRF wind field has several spots exceeding 96 kt, so the simulated cyclone is a major (cat 3) hurricane.  The XOVWM retrieval exceeded 96 kt in one of those small spots, northwest of the center, although it didn't capture the other  96-kt areas east of the center where the maximum wind probably was (a mild disappointment, but I'm not really complaining).  This means that, if this was an actual XOVWM overpass, it would have correctly estimated that this is a category 3 hurricane.

## Wind Radii – Katrina Example

- 50kts
- 64kts

- QuikSCAT
- XOVWM
- WRF

**50kts**

**50kts**

**64kts**

**Wind Radii – Katrina Example**

## QuikSCAT and XOVWM vs WRF Wind Speeds

**QuikSCAT and XOVWM vs WRF Wind Speeds**

**XOVWM vs WRF**

**QuikSCAT vs WRF**

## Rita – 5th Example 9/22/05 15:30

**Rita – 5****th**** Example 9/22/05 15:30**

**Notes:**
Following hurricane Rita on 21th, 22th and 23rd of September 2005 5 measurement and retrieval simulation examples were generated for QuikSCAT-like and next generation wind sensor (XOVWM). The example from 9/22/05 15:30 UTC shows WRF surface wind field and corresponding QuikSCAT-like retrievals. It is readily noted that although size of the storm is properly retrieved storm structure is distorted as we move towards the storm center. Very small inner wall and eye is completely missed and storm center is moved ~60nm towards SW from center depicted in WRF field. This is very typical of QuikSCAT retrievals as we see them today. 

## Rita – 5th Example 9/22/05 15:30

**Rita – 5****th**** Example 9/22/05 15:30**

**Notes:**
WRF surface wind field and corresponding XOVWM retrievals. 

## Wind Radii – Rita Example

- 34kts
- 50kts
- 64kts

- QuikSCAT
- XOVWM
- WRF

**Wind Radii – Rita Example**

**34kts**

**50kts**

**64kts**

**34kts**

**50kts**

**64kts**

## QSCAT vs WRF Wind Speeds for Rita Simulations

- QuikSCAT significantly underestimates high wind speeds. The different plots show Hurricane Rita at different times of its evolution.

**QSCAT vs WRF Wind Speeds for Rita Simulations**

## XOVWM vs WRF Wind Speeds for Rita Simulations

## Max Wind

- WRF
- XOVWM
- QuikSCAT

- 09:21:15:30

- 09:21:21:30

- 09:22:3:30

- 09:22:9:30

- 09:22:15:30

**Notes:**
Max wind speed retrievals for 5 Rita simulation times between 09/21-09/22. Max wind speeds from WRF simulations were between 100-110kts (cat 3). Max winds from XOVWM were in the range between 97-113kts. Although somewhat lower these retrievals will also indicate cat 3 hurricane
QuikSCAT max retrievals were between 65-90kts. 88kts retrievals were obtained only for first example indicating cat 2 hurricane for othe 4 examples all max wind retrievals were between 65-75kts indicating cat 1 hurricane.

## Helene – 09/22/2006 9:30UTC

## Helene – 09/22/2006 9:30UTC

## Helene – 09/22/2006 9:30UTC

## Coastal Simulation Studies

**Study description:**
- Use NOGAPS model wind complemented with SAR 500m resolution wind speed observations to simulate XOVWM and QuikSCAT data (SAR does not provide direction data and has limited temporal coverage.)
- Primary data (Alaska) selected by NOAA based on known hazardous coastal winds in shipping lanes and fisheries. The Alaska coast near Juneau and Sitka has frequent strong coastal winds which affect the safety of shipping and fishing boats.
- Additional data (California & Oregon) selected based on known highly variable coastal winds
**Coastal Masks**
- QuikSCAT measures winds only up to 20 km from the coast, and cannot meet the coastal winds needs
- XOVWM can measure winds up to 2.5km of the coast

## Alaska CoastCurrently Available Routine Data Availability

- Model winds are routinely available at low resolution, which fail to capture high speed coastal winds and variability

- Occasionally, SAR wind speed data (no directions) are available that give an indication of the true wind variability. Note speeds do not agree with model.

## SAR Winds + NOGAPS Directions

**SAR Winds + NOGAPS Directions**

**QuikSCAT-like Retrievals**

## XOVWM Retrievals

**XOVWM Retrievals**

**SAR Winds + NOGAPS Directions**

## Alaska Coast SAR Winds and Simulations  

**QuikSCAT-like Retrievals**

**SAR Winds + NOGAPS Directions**

**Alaska Coast SAR Winds and Simulations  **

**Notes:**
NNW flow event across Shelikof Strait and the southern portion of Cook Inlet.  Several intense areas of gap flows are evident, two in Shelokif Strait and the major flow in the lee of Kamishak Bay to Iliamna Bay.  The SAR shows winds to Hurricane Force extending aboiut half way across Cook Inlet and strong GALE to STORM force to the east of the northern tip of Kodiak Island.  The XOVWM does an excellent job on this scale and picks up all of the outflow plumes seen in the SAR.  Intensities are similar with HF and STORM force in similar areas.  The two outflow plumes in Shelikof Strait also appear ot be quite similar.  The sharp gradient of wind across the southern Cook Inlet is well depicted by XOVWM.  
In comparison the QuikSCAT simulation smooths the gradient out across southern Cook Inlet and is too high with the wind minima there.  HF winds are seen but the extent of storm force is not as far to the SE as XOVWM and SAR.  The land contamination and mask limits retrievals in Shelikof Strait with one smaller outflow plume being missed. 

## Alaska Coast SAR Winds and Simulations  

**XOVWM Retrievals**

**SAR Winds + NOGAPS Directions**

**Alaska Coast SAR Winds and Simulations  **

**Notes:**
NNW flow event across Shelikof Strait and the southern portion of Cook Inlet.  Several intense areas of gap flows are evident, two in Shelokif Strait and the major flow in the lee of Kamishak Bay to Iliamna Bay.  The SAR shows winds to Hurricane Force extending aboiut half way across Cook Inlet and strong GALE to STORM force to the east of the northern tip of Kodiak Island.  The XOVWM does an excellent job on this scale and picks up all of the outflow plumes seen in the SAR.  Intensities are similar with HF and STORM force in similar areas.  The two outflow plumes in Shelikof Strait also appear ot be quite similar.  The sharp gradient of wind across the southern Cook Inlet is well depicted by XOVWM.  
In comparison the QuikSCAT simulation smooths the gradient out across southern Cook Inlet and is too high with the wind minima there.  HF winds are seen but the extent of storm force is not as far to the SE as XOVWM and SAR.  The land contamination and mask limits retrievals in Shelikof Strait with one smaller outflow plume being missed. 

## SE Alaska Coast SAR Winds and Simulations  

**QuikSCAT-like Retrievals**

**SAR Winds + NOGAPS Directions**

**SE Alaska Coast SAR Winds and Simulations  **

**Notes:**
Offshore flow along the SE Alaska Coast from Chicagof Island to just SE of Yakutat with multiple plumes of gap winds.  Two major plumes are depicted by all instruments in the lee of Cross Sound and Icy Point.  These are depicted by all three simulations and extend well into the offshore waters.  Three narrower gap flows or plumes can be seen to the NW of the major outflow with a weaker outflow to the SE of Cross Sound extending to the WSW of Cape Edward.  The XOVWM portrays each of these gap flows.  QuikSCAT due to the landmask only shows the smooth offshore portion of these flows.  In fact the two plumes from Cross Sound to Icy Point are depicted as a single plume.  The three plumes to the NW are really only hinted at. 

## SE Alaska Coast SAR Winds and Simulations  

**XOVWM Retrievals**

**SAR Winds + NOGAPS Directions**

**SE Alaska Coast SAR Winds and Simulations  **

**Notes:**
Offshore flow along the SE Alaska Coast from Chicagof Island to just SE of Yakutat with multiple plumes of gap winds.  Two major plumes are depicted by all instruments in the lee of Cross Sound and Icy Point.  These are depicted by all three simulations and extend well into the offshore waters.  Three narrower gap flows or plumes can be seen to the NW of the major outflow with a weaker outflow to the SE of Cross Sound extending to the WSW of Cape Edward.  The XOVWM portrays each of these gap flows.  QuikSCAT due to the landmask only shows the smooth offshore portion of these flows.  In fact the two plumes from Cross Sound to Icy Point are depicted as a single plume.  The three plumes to the NW are really only hinted at. 

**Notes:**
Wind Speed retrieval errors with respect to the retrieval resolution and mission requirements. These plots are showing that if lower resolution products were produced from an instrument that is capable of retrieving with at higher resolution (5km in XOVWM) case. 4 times lower resolution leads to 4 times lower wind speed error

**Notes:**
Same as previous slide but for wind direction error

## Requirements Importance

-     **Increased resolution and decreased sensitivity to rain will allow for:**
- More reliable **estimates of tropical cyclone intensity through all stages of development**  tropical depressions, tropical storms, hurricanes and potentially major hurricanes
- Improved analysis of tropical cyclone wind field structure (**34, 50, and 64 kt radii**)  more refined watch/warning areas for the coast
- More accurate **tracking of tropical cyclone centers and earlier identification of developing TCs**  more accurate initial motion estimates as input into model guidance
- More accurate **maximum wind estimates of extratropical cyclones** and distribution of all warning categories

**Notes:**
Image shows intensity of Katrina at landfall uncertainity due to large spread of intensity estimates on 29 August from aircraft, radar, and satellite
Improved satellite ocean surface vector wind data could result in more accurate intensity and structure analysis, important for improving and verifying model forecasts of intensity and structure

## Wind field associated with both organized convection such as squall lines and less organized convection

Wind field in the vicinity of ocean surface thermal features such as warm and cold rings, fronts, and currents

Significantly better definition of coastal wind features including orographically induced or enhanced low level jets

Significantly better definition of ocean forcing for areas such as upwelling along coastlines

Wind field associated with smaller scale features such as polar lows

- Wind field in the vicinity of ocean **surface thermal features** such as warm and cold rings, fronts, and currents
- Significantly better definition of coastal wind features including **orographically induced or enhanced low level jets**
- Significantly **better definition of ocean forcing** for areas such as upwelling along coastlines
- Wind field associated with smaller scale features such as polar lows

**Requirements Importance - Continued**

- Plots courtesy of JPL

## Conclusions

- Much progress has been made in the last year
- •	**However, there is no guarantee at this point that there will be an ocean vector winds mission after QuikSCAT ends*** *
- The scatterometer is competing against many different instruments with active user communities in a limited funding environment
- •	The science and operational requirement justifications for a follow-on scatterometer OSVW mission must continue to be made
**The following year will be key for advocacy by the science and operational communities**
**The end users must be an integral and active part of the next steps**
**These activities need to be sustained**

## Recommendations for Consideration

**Elevate the priority, accelerate and approve plans** **for continuous** **OSVW missions**** **to minimize the data gap and continue improvements in weather forecasting and warning capabilities and climate studies realized today,
**Fund the Extended Ocean Vector Winds Mission** **(XOVWM)** as recommended by the National Research Council and designed and presented in a study by NASA’s  Jet Propulsion Laboratory to overcome limitations in current measurement capabilities and advance improvements in weather forecasting especially in coastal zones and hurricanes
- User impact studies need to continue beyond the completion of the QuikSCAT follow-on study that NASA-JPL is conducting for NOAA.