The Need for an Advanced Sounder on GOES

The Numerical Weather Prediction PerspectiveRobert M. AuneCenter for Satellite Applications and Research, NESDIS

For GUC6 Panel Discussion3 – 5 November 2009Madison, Wisconsin

UW-Madison

► How can a GEO sounder be used to improve numerical weather prediction (NWP)?

► Operational use of GOES sounders at EMC

► New application – Near-Casting

► What does HES bring to NWP?

► Future

Hyper-spectral Sounder

GOES Sounder ImagesP

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UW/CIMSS

A high spectral resolution advanced sounder would have more and sharper weighting functions compared to current GOES sounder.

Current GOES (18)

Weighting Functions

GOES-I P (Q?) Sounders

Computing brightness temperatures from model output provides a link between the forecast

model and reality as seen by satellites

GOESTRAN, a 101-level radiative transfer model, is used to compute 6.7μ brightness temperatures. Model temperatures and mixing ratios are used as input. Transmittance coefficients for GOES-11 and GOES-12 are used. Clear sky only.

11μ (window) images are generated by applying a vertically integrated, cloud-mass weighted transmissivity to the model predicted skin temperature. If the cloud mass exceeds a threshold, the radiating temperature is set to the model layer temperature.

Forecast 11μ (window) images (top) from the CIMSS Regional Assimilation System. Validating images (bottom) are shown with the same enhancement.

Forecast 6.7μ cloud-clear water vapor images (top) from the CIMSS Regional Assimilation System. Validating images (bottom) are shown with the same enhancement.

To improve forecast accuracy the North America CRAS is now assimilating each GOES sounder scan

at each specific central scan time.

CRAS forecast IR image from 12-hour spin-up forecast commencing 00UTC 13Jun08, 10-min frames.

Initializing Water Vapor and Clouds in the South America CRAS using Precipitable Water and

Cloud-top Pressure from the GOES-10 SounderGOES-10

12-hour loop of total precipitable water images showing the hourly adjustments to water vapor due to the assimilation of GOES-10 sounder products.

12-hour loop of simulated 11 micron images showing the hourly cloud adjustments due to the assimilation of GOES-10 sounder products.

CRAS analysis cycle CRAS analysis cycle

Assimilating Precipitable Water fromthe GOES sounder

36-hour forecast rain-rate loop (mm/hr) fromthe CIMSS Regional Assimilation System (CRAS) commencing 12:00 UTC, April 13, 2006. Intense convection was predicted 13 hours into the forecast for Eastern Iowa. In this case the moisture gradients in the CRAS initial conditions were accurately specified by assimilating 3-layer precipitable water from the GOES sounder.

Composite Radar Summary (dBz) valid 00:45 UTC, April 14, 2006. (Courtesy of Unisys Weather).

TORNADO WARNING  NATIONAL WEATHER SERVICE QUAD CITIES IA IL  823 PM CDT THU APR 13 2006THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A TORNADO WARNING FOR WESTERN MUSCATINE COUNTY IN EAST CENTRAL IOWA UNTIL 930 PM CDT.  AT 820 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A TORNADO 15 MILES WEST OF NICHOLS...OR ABOUT 8 MILES SOUTH OF IOWA CITY...MOVING EAST AT 35 MPH.  

3-Layer Precipitable Water from GOES Sounders Improves NCEP Eta Forecasts

Impact of GOES-8/9 PW on 12hr Eta Forecast RHVs. RAOBs (West)

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A negative rms error difference indicates an improved forecast

Robert Aune (NESDIS) and Eric Rodgers (NWS)

1-h fcst w/o GOES cloud assim

1-h fcst w/ hourly GOES cloud assim NESDIS cloud-top (verification)

RUC 1-hour cloud-top pressure (hPa) forecasts with and without GOES sounder cloud-top pressure assimilation valid 1200 UTC 14 May 1999. Clearing and building are performed.

Cloud Initialization in the Rapid Update Cycle (RUC)

A comparison of GOES sounder precipitable water

to NCEP NAM initial conditions

Initial precipitable water, NAM

Initial precipitable water differencesGOES sounder TPW minus NAM

GOES sounder TPW vs NAM

GOAL:Generate useful short-range forecasts of the timing and locations

of severe thunderstorms

Issues:- Poor forecast accuracy in short-range NWP

- Lack of moisture observations over land (US)

- Excessive smoothing of moisture in NWP

- Time delay in delivering guidance products

Solution:Develop an objective “nearcasting” tool that leverages information from the GOES Sounder to assist forecasters with identifying pre-convective environments 1-6 hours in advance

Using the GOES Sounder to Nearcast Severe Using the GOES Sounder to Nearcast Severe WeatherWeather

Fill the GapBetween Nowcasting & NWP

CIMSS collaborator: Ralph Petersen

New example of advantage of Equivalent Potential temperature ( Theta-E or Θe )Theta-E measures TOTAL moist energy in

atmosphere, not only latent heat

Low-level Theta-E NearCasts shows warm / moist air band moving into far NW Iowa, where deep convection formed rapidly by 2100 UTC.

Vertical Theta-E Difference shows complete convective instability - GOES temperature data adding information to vertical moisture gradient data used earlier.

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6 hr NearCast for 2100 UTCLow to Mid level Theta-E Differences

6 hr NearCast for 2100 UTCLow level Theta-E

6 hr NearCast for 2100 UTCLow to Mid level PW Difference

Rapid Development of Convection over NE IA between 2000 and 2100 UTC 9 July 2009

Using the GOES Sounder to Nearcast Severe Using the GOES Sounder to Nearcast Severe WeatherWeather

Poster byRalph Petersen and Robert Aune

Real-time 6-hour nearcast of atmospheric de-stabilization, 2-layer thetaE from the GOES-12 sounder commencing 19UTC Novenber 3, 2009. Hourly loop is from T- 6 hours to T+ 6 hours.

GOES Sounder Nearcasts of Convective GOES Sounder Nearcasts of Convective Destabilization In AWIPSDestabilization In AWIPS

Significance:

Nearcasting severe weather up to 6 hours in advance fills the gap between nowcasting observations and numerical weather prediction. It supports NOAA’s Weather and Water mission goal.

GOES sounder nearcast products are now available in AWIPS in real-time. An AWIPS display of precipitable water lapse rate is shown.

Photo voltaic arrays need nearcasts of cloud shadows to maintain load levels

Nearcasting Shadows for the Solar Power Industry

Using GOES imager and sounder cloud products in a nearcasting model

Knowing each plant’s rated output, nearcasts of cloud cover can be used to compute the actual output of each plant in real time.

The CIMSS Regional Assimilation System (CRAS) uses cloud and water vapor observations from GOES to define initial cloud fields. CRAS forecast tendencies are used to drive a Lagrangian cloud trajectory model to nearcast cloud optical depth and surface solar fluxes.

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CRAS forecast cloud cover (%)

UW-Madison

What does a geostationary hyper-spectral sounder bring to numerical weather prediction?

1. VERTICAL RESOLUTION!

UW-Madison

What does a geostationary hyper-spectral sounder bring to numerical weather prediction?

1. VERTICAL RESOLUTION!

2. VERTICAL RESOLUTION!!

UW-Madison

What does a geostationary hyper-spectral sounder bring to numerical weather prediction?

1. VERTICAL RESOLUTION!

2. VERTICAL RESOLUTION!!

3. VERTICAL RESOLUTION!!!

Improvements in Retrievals with Interferometers

Temperature errors less than 1 degree are only available from

high spectral resolution measurements

RH errors less than 10% are only available from high spectral resolution measurements

Model background not required!

Compatible with modern assimilation

techniques!

An Observing System Simulation Experiment (OSSE) to Test the Impact

of a GeostationaryHyper-Spectral Sounder

Goal: Assess the potential impact of Geo Interferometer

“Nature” Forecast: UW NMM Model

Simulated Observations:Soundings (T, Td) from GOES (18 channels)Soundings (T, Td) from GIFT (2000 channels)

Insitu Observations:Winds (cloud drift / water vapor)Aircraft Reports (T, winds)Profiler Network (T, Td)Sfc obs, RAOBs

Assimilating Model:Rapid Update Cycle (RUC) 12-hour forecasts with different combinations of observations were compared to assess impact

Significant Finding from Geo-Interferometer OSSE

Geo Interferometer penetrates Boundary Layer (BL) to provide low level (850 RH) moisture information:

Geo Radiometer only offers information above BL (700 RH)

UW-Madison/CIMSS

All three solutions show rapid atmospheric destabilization (decreasing LI) between 14 and 20 UTC. GIFTS better depicts the absolute values and tendencies compared to GOES. The total precipitable water (TPW) increases through the period. Both current and future sounding measurements capture the correct trends.

3 May 1999 -- Oklahoma/Kansas tornado outbreakARM / CART Site

IMG demonstrates interferometer capability to detect low level inversions: example over Ontario with inversion (absorption line BTs warmer) and Texas without (abs line BTs colder)

UW-Madison

The top seven observing systems that contribute to ECMWF forecast error reduction (QJRMS, Oct, 2009):

1. AMSU-A (4 satellites)  17.2% 2. IASI (one satellite) 12.0% 3. AIRS (one satellite) 11.8% 4. AIRREP (aircraft temperature and winds) 9.3% 5. GPSRO (bending angles)-8.5% 6. TEMP (radiosonde winds, humidity, and temps)-7.9% 7. QuikSCAT (scatterometer surface winds)-5.2%

Hot off the press!

UW-Madison

Summary

A geostationary hyper-spectral sounder (upstream of North America) will provide the greatest improvement in 24-48 hour forecast accuracy in the history of operational mesoscale NWP at NCEP!

1. Enable assimilation of T, Td retrievals2. Retrievals over water AND land3. 15 minutes between scans4. See deeper into the atmosphere5. Allow above cloud retrievals6. Improved height assignment of satwinds7. Provide additional tracers for satwinds