The Need for an Advanced Sounder on GOES

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The Need for an Advanced Sounder on GOES The
Numerical Weather Prediction Perspective
Robert M. Aune Center for Satellite Applications
and Research, NESDIS For GUC6 Panel Discussion 3
5 November 2009 Madison, Wisconsin
? 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
UW-Madison
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GOES Sounder Images
GOES-I P (Q?) Sounders
A high spectral resolution advanced sounder would
have more and sharper weighting functions
compared to current GOES sounder.
Current GOES (18)
Pressure (hPa)
Pressure (hPa)
Weighting Functions
UW/CIMSS
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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.
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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.
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Initializing Water Vapor and Clouds in the South
America CRAS using Precipitable Water and
Cloud-top Pressure from the GOES-10 Sounder
GOES-10
CRAS analysis cycle
CRAS analysis cycle
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.
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Assimilating Precipitable Water from the GOES
sounder
TORNADO WARNING  NATIONAL WEATHER SERVICE QUAD
CITIES IA IL  823 PM CDT THU APR 13 2006 THE
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.  
36-hour forecast rain-rate loop (mm/hr) from the
CIMSS Regional Assimilation System (CRAS)
commencing 1200 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 0045 UTC,
April 14, 2006. (Courtesy of Unisys Weather).
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3-Layer Precipitable Water from GOES Sounders
Improves NCEP Eta Forecasts
Robert Aune (NESDIS) and Eric Rodgers (NWS)
A negative rms error difference indicates an
improved forecast
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Cloud Initialization in the Rapid Update Cycle
(RUC)
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.
1-h fcst w/o GOES cloud assim
1-h fcst w/ hourly GOES cloud assim
NESDIS cloud-top (verification)
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A comparison of GOES sounder precipitable water
to NCEP NAM initial conditions
Initial precipitable water, NAM
GOES sounder TPW vs NAM
Initial precipitable water differences GOES
sounder TPW minus NAM
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Using the GOES Sounder to Nearcast Severe Weather

• GOAL
• Generate useful short-range forecasts of the
  timing and locations
• of severe thunderstorms

Fill the Gap Between Nowcasting NWP

• 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
CIMSS collaborator Ralph Petersen
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Using the GOES Sounder to Nearcast Severe Weather
Poster by Ralph Petersen and Robert Aune
New example of advantage of Equivalent Potential
temperature ( Theta-E or Te )
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.
6 hr NearCast for 2100 UTC Low level Theta-E
Negative ?Te/?Z (blue to red areas) indicates
Convective Instability
Rapid Development of Convection over NE IA
between 2000 and 2100 UTC 9 July 2009
6 hr NearCast for 2100 UTC Low to Mid level
Theta-E Differences
6 hr NearCast for 2100 UTC Low to Mid level PW
Difference
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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.
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GOES Sounder Nearcasts of Convective
Destabilization In AWIPS
GOES sounder nearcast products are now available
in AWIPS in real-time. An AWIPS display of
precipitable water lapse rate is shown.
Significance Nearcasting severe weather up to 6
hours in advance fills the gap between nowcasting
observations and numerical weather prediction.
It supports NOAAs Weather and Water mission
goal.
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Nearcasting Shadows for the Solar Power Industry
Using GOES imager and sounder cloud products in
a nearcasting model
CRAS forecast cloud cover ()
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.

Knowing each plants rated output, nearcasts of
cloud cover can be used to compute the actual
output of each plant in real time.
Photo voltaic arrays need nearcasts of cloud
shadows to maintain load levels
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What does a geostationary hyper-spectral sounder
bring to numerical weather prediction? 1.
VERTICAL RESOLUTION!
UW-Madison
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What does a geostationary hyper-spectral sounder
bring to numerical weather prediction? 1.
VERTICAL RESOLUTION! 2. VERTICAL
RESOLUTION!!
UW-Madison
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What does a geostationary hyper-spectral sounder
bring to numerical weather prediction? 1.
VERTICAL RESOLUTION! 2. VERTICAL
RESOLUTION!! 3. VERTICAL RESOLUTION!!!
UW-Madison
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Improvements in Retrievals with Interferometers
Model background not required!
RH errors less than 10 are only available from
high spectral resolution measurements
Temperature errors less than 1 degree are only
available from high spectral resolution
measurements
Compatible with modern assimilation techniques!
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An Observing System Simulation Experiment (OSSE)
to Test the Impact of a GeostationaryHyper-Spectr
al 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
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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)
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3 May 1999 -- Oklahoma/Kansas tornado
outbreak ARM / CART Site
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.
UW-Madison/CIMSS
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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)
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Hot off the press!
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
UW-Madison
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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 retrievals
2. Retrievals over water AND land
3. 15 minutes between scans
4. See deeper into the atmosphere
5. Allow above cloud retrievals
6. Improved height assignment of satwinds
7. Provide additional tracers for satwinds

UW-Madison