The Use of WSR88D 1hour StormTotal Precipitation Estimates for Near RealTime Quality Assurance QA of

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The Use of WSR-88D 1-hour Storm-Total
Precipitation Estimates for Near Real-Time
Quality Assurance (QA) of Meteorological Surface
Network Rainfall Observations
Kenny L. Tapp Oklahoma Climatological
Survey University of Oklahoma

• Mesonet Rainfall Measurements
• UNITS Millimeters of water per day
• DESCRIPTION The total amount of rainfall
  measured since 0000 GMT 6 PM CST or 7 PM CDT
  just above the ground it is measured in discrete
  tips of the bucket (approximately 0.01 inch per
  tip, or 0.254 millimeters).
• NOTES
• Each Mesonet observation contains a running
  accumulation of rainfall since either 6 PM CST or
  7 PM CDT. As each new evening begins, the
  accumulated rainfall is reset to zero.
• If the rainfall is very light, the bucket may
  only tip once every half hour or so. Thus, even
  if the rain is continuous, rainfall might be
  recorded during every other 15-minute interval.
  If the rainfall is very heavy, there is a strong
  likelihood that rain has splashed out of the
  bucket. Thus, measurements during heavy rainfall
  periods generally underestimate the total amount
  of rainfall.
• Unheated gauges were chosen because of
  constraints on cost and power the
• drawback is that unheated gauges underestimate
  snow or freezing rain totals.
• In addition, wet snow can clog the
• bucket while dry snow often blows
• away. Moreover, once air
• temperatures rise above freezing,
• the water equivalent of the
• melting precipitation is
• finally measured. The result is
• a delayed measurement of winter precipitation.

• Objectives for Research
• Select 10-12 case-study events that are
  representative of typical rain gauge QA problems.
• Develop time series graphs from a given pixel
  using WSR-88D data.
• Quantify spatial and temporal variability of
  rainfall estimates and measurements from Mesonet
  and WSR-88D.
• Adapt and test, for near real-time operation, the
  technique developed and currently used for manual
  QA of Oklahoma Mesonet rainfall observations.

• Oklahoma Mesonet
• Over 117 automated stations covering Oklahoma.
• Over 3,179,425,701 observationssince January
  1st, 1994.
• Measurements are packaged into "observations"
  every 5 minutes, then transmitted to a central
  facility every 15 minutes, 24 hours per day
  year-round. 
• A site consists of a 100 square-meter plot of
  land, one 10-meter metal tower, a lightning rod,
  solar panel, battery, radio transmitter, data
  logger, instruments attached to the tower,
  instruments near the tower buried underground,
  and a ground-mounted rain gauge surrounded by a
  wind screen.
• Future Applications Use GPS receivers to .
  estimate local water vapor (NERON), .
  Skin Surface Temperature for Road .
  Weather Info.

• Radar 1-hr. Rainfall Measurements
• NOTES
• Estimated one-hour precipitation accumulation is
  on a 1.1 nm by 1 degree grid.
• This product is used to assess rainfall
  intensities for flash flood warnings, urban flood
  statements and special weather statements.
• The maximum range of this product is 124 nm
  (about 143 miles) from the radar location.

Prepared for COSMIC Camp, SU 2005