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High resolution radar data and products over the Continental United States. Valliappa.Lakshmanan@noaa.gov National Severe Storms Laboratory Norman OK, USA http://w ww.wdssii.org/. Evolution of WDSS. What products? How often?. Products: Gridded hail products

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high resolution radar data and products over the continental united states

High resolution radar data and products over the Continental United States

Valliappa.Lakshmanan@noaa.gov

National Severe Storms Laboratory

Norman OK, USA

http://www.wdssii.org/

evolution of wdss
Evolution of WDSS

lakshman@ou.edu

what products how often
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

lakshman@ou.edu

how does it work
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.

lakshman@ou.edu

virtual volume composite
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.

at19.5

at0.5

lakshman@ou.edu

why do qc
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.

lakshman@ou.edu

impact of qc
Impact of QC

raw

With QC’ed composites

  • 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.

lakshman@ou.edu

second level of qc
Second level of QC
  • The radar QC is conservative
    • Doesn’t 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

lakshman@ou.edu

what do we do with the composite
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.

lakshman@ou.edu

2d vs 3d
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

lakshman@ou.edu

the 3d flow
The 3D flow
  • Not just reflectivity.
  • Compute shear (Smith05) and low-level shear.
  • Process lightning

lakshman@ou.edu

3d processing
3D processing
  • Combine QC’ed 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.

lakshman@ou.edu

example products
Example products
  • Extracted from the real-time generation on Jan. 11, 2006
    • The day I created this presentation!
    • We haven’t run the CONUS system in Spring yet, so the severe weather products may be underwhelming.

lakshman@ou.edu

reflectivity products
Reflectivity products

Composite from 2D

Composite from 3D

Which radars?

Height of Max Ref

lakshman@ou.edu

azimuthal shear products
Azimuthal shear products

30 minute rotation tracks

Azimuthal shear 0-3km MSL

lakshman@ou.edu

severe weather diagnosis
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)

lakshman@ou.edu

short term forecast
Short-term forecast

Reflectivity at T=0

Clusters

Southward motion

Reflectivity at T=30 (forecast)

lakshman@ou.edu

precipitation estimates
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

lakshman@ou.edu

what do we do with these products
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!

lakshman@ou.edu