High%20resolution%20radar%20data%20and%20products%20over%20the%20Continental%20United%20States

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High resolution radar data and products over the
Continental United States

• Valliappa.Lakshmanan_at_noaa.gov
• National Severe Storms Laboratory
• Norman OK, USA
• http//www.wdssii.org/

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Evolution of WDSS
1993-1998 Single-radar SCIT, MDA, TDA Now part of RPG
1995-2000 Single-radar with multi-sensor input NSE inputs Scheduled for ORPG-8
2003 Multi-radar multi-sensor over regional domain (1000km x 1000 km) Gridded products Shipped to select WFOs Used in Storm Pred. Center Product gen. for AWIPS?
2005 Multi-radar multi-sensor over CONUS CONUS 1km grids Available on the Internet Used in SPC
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What products? How often?

• Products
• Gridded hail products
• Reflectivity at constant temperature levels and
  layer averages
• Low-level and mid-level shear and rotation tracks
• Short-term forecast fields
• Lightning Density
• More
• Spatial Resolution
• 0.01 deg x 0.01 deg x 1km resolution
• Approximately 1km x 1km throughout Continental
  United States.
• 1km in height
• Temporal resolution
• 2D reflectivity mosaics every 2 minutes
• 3D and derived products every 5 minutes

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How does it work?

• The process for creating 2D composites
• Ingest Level-II radar data tilt by tilt
• QC reflectivity data (Lak06, JAM, review)
• Create virtual volume composites
• Merge composites from all the CONUS radars
  (Lak06, WF, accepted)
• 2nd level of QC -- using satellite and surface
  temperature data.

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Virtual volume composite

• In a traditional composite,
• Process volume-by-volume.
• Take maximum of all tilts.
• Need to wait for end of volume.
• In a virtual volume composite
• Process tilt-by-tilt.
• Keep a running volume.
• Replace older data each time.
• Take maximum of most current tilts.
• No need to wait for end of volume scan.
• A virtual volume provides more timely data.

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Why do QC?

• On a single-radar product, users may
• want to see clear-air returns.
• tolerate more clutter
• tolerate test patterns, etc.
• On a multi-radar product, clutter and clear-air
  returns are distracting.

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Impact of QC
With QCed composites
raw

• Left What we would get if directly combined raw
  (virtual volume) reflectivity composite data
• Clear-air return, sun strobes, test patterns
• Right combining QCed virtual volume reflectivity
  composite
• The QC is performed radar-by-radar
• Takes into account terrain, texture and vertical
  structure.

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Second level of QC

• The radar QC is conservative
• Doesnt always remove non-precipitation echo
• Especially if it is biological i.e. moving.
• A second level of QC looks at satellite and
  surface temperature and retains echo where there
  is likely to be clouds.

Bad data (bloom)
No clouds
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What do we do with the composite?

• The 2D radar mosaic is created every 2 minutes at
  1km resolution.
• Converted to Grib2 and sent to the SPC.
• Put on the Internet
• Snapshots with map background
• Converted to Geotiff
• Loadable with Google Earth or any GIS software.
• Google Earth does real-time loading
• Talk in IIPS on Tuesday
• http//wdssii.nssl.noaa.gov
• Not 24x7
• The software is licensed by some private
  companies
• They run it on their own machines.
• They take care of 24x7 reliability.

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2D vs 3D

• The 2D composite is cheap to create
• 5 dual-Xeon machines with 6 GB RAM
• But always provides an underestimate of true
  values.
• Need to compute in 3D
• Height of dBZ value important!
• Can incorporate NSE information by height
• A lot more products!
• The 3D products need
• 5 dual-Xeon with 6 GB RAM
• 2 dual-Xeon with 16 GB RAM
• 64-bit architecture

• composite from 2D 45 dBZ
• composite from 3D 50 dBZ

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The 3D flow

• Not just reflectivity.
• Compute shear (Smith05) and low-level shear.
• Process lightning

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3D processing

• Combine QCed reflectivity in 3D
• Combine AzShear in 3D
• Compute hail diagnosis and layer averages.
• Compute storm motion from composite.
• Use it to advect storms for short-term forecast.

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Example products

• Extracted from the real-time generation on Jan.
  11, 2006
• The day I created this presentation!
• We havent run the CONUS system in Spring yet, so
  the severe weather products may be underwhelming.

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Reflectivity products
Composite from 2D
Composite from 3D
Which radars?
Height of Max Ref
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Azimuthal shear products
30 minute rotation tracks
Azimuthal shear 0-3km MSL
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Severe weather diagnosis

• Also
• Probability of Severe Hail
• Maximum Expected Hail Size
• VIL_Density
• VIL_of_the_day
• Other echo top dBZ levels

Reflectivity at temp. levels
VIL
Convection
Echo top (18 dBZ)
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Short-term forecast
Reflectivity at T0
Clusters
Southward motion
Reflectivity at T30 (forecast)
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Precipitation estimates
Instantaneous precip rate
Ref closest to ground

• Just the 88D algorithm on CONUS
• Uses hybrid scan reflectivity
• Convective/stratiform segregration based on
  presence of hail
• 88D Z/R relationships.
• Not multi-sensor
• QPESUMS-II under development at NSSL.

2hr precip accum
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What do we do with these products?

• The 3D products are created every 5 minutes
• 1km resolution (0.01deg x 0.01deg x 1km)
• Converted to Grib2 and sent to the SPC.
• Put on the Internet (not all of them)
• Snapshots with map background
• Converted to Geotiff
• Loadable with Google Earth or any GIS software.
• Google Earth does real-time loading
• Talk in IIPS on Tuesday
• http//wdssii.nssl.noaa.gov
• Looking for the NWS to pick this up!