# Presentation: 813586

## XOVWM User Impact StudyRita Simulations9/21/05:15:30 – 09/22/05:15:30

- Contacts:
- _[Zorana.Jelenak@noaa.gov](mailto:Zorana.Jelenak@noaa.gov)_
- _Paul.S.Chang@noaa.gov_

## QuikSCAT Follow-On Mission Options

**QuikSCAT Follow-On Mission Options**

**	****In June 2007, NOAA asked JPL to conduct a study to provide the technical readiness, cost, and impact to NOAA of (1M investment):**
**A QuikSCAT equivalent re-flight**
**An Extended Ocean Vector Winds Mission (XOVWM) **
**A constellation (2) of XOVWM instruments**
**A draft of the final report documenting results of this study will be ready by January, 2008**

## XOWVM Impact Study

- As part of JPL study user input is needed regarding proposed mission options
- Input desired by 4th of January
- Mini wind workshop held at the end of NOAA Hurricane conference and study results were presented
- GoTo meetings are set up to reach as many interested users as possible
- Written statements from offices are desired addressing the following questions:
- What realized impacts on your daily work would be continued if QuikSCAT-like instrument is launched (swell forecast?, )
- Based on simulation results presented what is perceived impact that new capability can bring to your areas of responsibility (no buoys in particular areas of interest, wind events affecting your particular region not observed so far...)
- Due to time limitations simulation study is limited in its scope. In order to get more comprehensive understanding of new capability what are simulations that would be of interest for your area of responsibilities

## 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 6

**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

## Rita – 1st Example 9/21/05 15:30

- WRF Surface wind field 3km resolution

- WRF Simulated Rain Rates

## Rita – 1st Example 9/21/05 15:30

## Rita – 2nd Example 9/21/05 21:30

- WRF Surface wind field 3km resolution

- WRF Simulated Rain Rates

## Rita – 2nd Example 9/21/05 21:30

## Rita – 3rd Example 9/22/05 3:30

- WRF Surface wind field 3km resolution

- WRF Simulated Rain Rates

## Rita – 3rd Example 9/22/05 3:30

## Rita – 4th Example 9/22/05 9:30

- WRF Surface wind field 3km resolution

- WRF Simulated Rain Rates

## Rita – 4th Example 9/22/05 9:30

## Rita – 5th Example 9/22/05 15:30

- WRF Surface wind field 3km resolution

- WRF Simulated Rain Rates

## Rita – 5th Example 9/22/05 15:30

## Wind Radii

- 34kts
- 50kts
- 64kts

- QuikSCAT
- XOVWM
- WRF

**Wind Radii**

**34kts**

**34kts**

**50kts**

**50kts**

**64kts**

**Notes:**
-34kts wind radii identified quite accurately with both instruments
-50kts radii identified from QuikSCAT retrievals substantially smaller than from XOVWM – warning area drastically reduced
-XOVWM identified hurricane double wall. Double wall is not just missing from QuikSCAT retrievals but wind speeds retrieved are 20kts lower in that area than in reality.

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

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

**Scatter Plots of****QSCAT Wind Speeds vs WRF Wind Speeds**

## Scatter Plots ofXOVWM Wind Speeds vs WRF Wind Speeds

## 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.

## Written Feedback on Following Questions is Desired by 4th of Jan ‘08

- What realized impacts on your daily work would be continued if QuikSCAT-like instrument is launched (swell forecast?, )
- Based on simulation results presented what is perceived impact that new capability can bring to your areas of responsibility (no buoys in particular areas of interest, wind events affecting your particular region not observed so far...)
- Due to time limitations simulation study is limited in its scope. In order to get more comprehensive understanding of new capability what are simulations that would be of interest for your area of responsibilities

**Additional information available at:**
_**http://manati.orbit.nesdis.noaa.gov/SVW_nextgen/osvw_mini_workshop.html**_