Applications of Radar Refractivity Retrievals: TwoYear Climatology of Boundary Layer Moisture

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Applications of Radar Refractivity Retrievals
Two-Year Climatology of Boundary Layer Moisture
David Bodine, Pamela L. Heinselman, Robert D.
Palmer, Boon Leng Cheong, Dan Michaud School of
Meteorology and Atmospheric Radar Research
CenterGraduate StudentUniversity of Oklahoma
Acknowledgements Support for this research was
provided by the Radar Operations Center, National
Science Foundation, and the American
Meteorological Society Fellowship Program.
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Motivation

• Problem One of the greatest challenges in
  meteorology is convective weather forecasting
  (Emanuel et al. 1995)
• Example QPF convective weather forecasts are
  worst in summer
• Reason Limited temporal and spatial resolution
  of moisture measurements hinders accuracy of
  convective weather forecasts

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Radar Refractivity

• Technique that uses ground clutter phase
  measurements to obtain refractivity (Fabry 2004,
  Cheong et al. 2008)
• Refractivity
• Radar refractivity 4-km spatial and 5-10 min.
  temporal resolution

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Algorithm Summary
Cheong et al 2008
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Applications of Refractivity Data

• Convection Initiation
• Boundary Identification and Tracking
• Supercells and Tornadogenesis
• Boundary Layer Moisture Characteristics

Heinselman et al. 2009
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Convection Initiation Case April 30, 2007
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Validation of Impact of Moisture Pool on
Convection Initiation

• Scenario 1 Average surface conditions (?Td0ºC)
• Scenario 2 Average Mesonet ?Td (?Td1.4ºC)
• Scenario 3 10 N-unit increase observed in radar
  refractivity (?Td2ºC)
• NSHARP analysis

1800 UTC 30 April 2007 LMT sounding
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Boundary Layer Moisture Studies

• Location KFDR
• Time Period 15 May - 31 July 2008 and 1 June -
  31 July 2009
• Objective Investigate diurnal characteristics of
  boundary layer moisture field and its
  interseasonal and intraseasonal variability

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Boundary Layer Moisture Evolution 3 June 2008
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Boundary Layer Moisture Spatial Variability

• Computed mean absolute deviation (MAD) of N and
  dN over different spatial scales (4-20 km)
• Histograms of one-hour averaged MAD

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W-E MAD of Refractivity

• MAD is higher over larger distances
• Slightly higher W-E moisture variability in 2008

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W-E MAD of Scan-to-scan Refractivity

• Almost no change in MAD with distance
• Increasing MAD between 14 and 19 UTC
• Slightly decreasing MAD after 19 UTC

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Moisture Field Movement and Spectral Analysis

• Wave-like features were often observed in the
  moisture field between 2000 and 0000 UTC
• What is the typical movement and wavelength of
  these features?
• 2D cross-correlation analysis velocity
• 2D Fourier analysis wavelength

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Refractivity-derived surface winds?

• Precipitation free period
• Good agreement with boundary layer and surface
  wind
• Possible near-surface wind retrieval using
  refractivity?

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Spectral analysis of moisture

• Study-long two-dimensional FFT
• Refractivity moisture field dominated by W-E
  moisture gradient
• Scan-to-scan peak wavelength between 10-15 km

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Summary of Boundary Layer Applications

• Statistical analysis of diurnal moisture changes
  showed
• Variability of moisture showed no diurnal trend
  and short-term moisture changes generally
  increased as the CBL developed
• Maximum variability in the afternoon
• Coherent BL structures can be tracked in
  scan-to-scan refractivity

Contact Info
David Bodine
bodine_at_ou.edu
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Moisture Field Movement
Wind Speed
Wind Direction