Impact of Doppler Velocities Assimilation on the Simulation of a Severe Winter Hailstorm Event

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Impact of Doppler Velocities Assimilation on the
Simulation of a Severe Winter Hailstorm Event
Hsin-Hung Lin , Pay-Liam Lin Department of
Atmospheric Sciences, National Central
University, Taiwan Bill Kuo and Qingnong
Xiao National Center for Atmospheric Research,
Boulder, Colorado
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Outline

• Introduction
• Methodology
• ?Processes of 3D-VAR Data Assimilation
• ?Impact of Precipitation Parameters
• Result
• ?Assimilation of Radial Velocity
• ?Case Simulation
• ?Sensitivity Test
• Summary

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• Why Do We Need to Assimilate Doppler Radar Data
• Remotely observing the Internal Structure of
  Precipitation Weather Systems.
• High Spatial and Temporal Resolution.
• Important for Mesoscale and Microscale Weather
  Analysis and Forecasting.
• Assimilation of Doppler Velocity
• Using MM5 NCAR 3D-VAR System to Assimilate
  Radial Velocity of NCU Doppler Weather Radar.
• Derived Rain Water Content from reflectivity to
  Modify Terminal Velocity in 3DVAR Process.
• To Improve the Precipitation Simulation.

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Assimilation of Radial Velocity
Observational Operator for Doppler Radial Velocity
Whats the influence of Liquid Water Content (qr)
on Vr Retrieval?
Sun Juanzhen Andrew Crook, 1997
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• Verification
• ?2003 6/14 Meiyu front Case

NCU RADAR Reflectivity
NCU Doppler Velocity
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• Comparison with Dual-Doppler Winds

Assimilated Vr
Non-Assimilated
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Case Simulation
2002 12/19 Hail Storm
Radial Velocity
Radar Reflectivity
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Evolution of Hail Storms
2002/12/19 10 15 UTC
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Sensitivity Test

• Compare AsVr With NoAs
• Compare IqAs With AsVr

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Wind Difference of AsVr and NoAs

• 1000 hPa
• Initial Field

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Wind Difference of AsVr and NoAs

• 850 hPa
• Initial Field

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Wind Difference of AsVr and NoAs

• 500 hPa
• Initial Field

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Using Radar Reflectivity to Retrieval qr and
Insert into MM5 Initial Field.
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Difference of IqAs and AsVr
Difference of Horizontal Wind Field. - Initial
Field With and Without qr
The Max. Wind Difference 11.5 m/s
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Difference of IqAs and AsVr
Difference of Vertical Velocity - Initial Field
With and Without qr
At 500 hPa, the Max. Difference about 0.1 m/s
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Result of Case Simulated with qr
Assimilated Vr
13Z
14Z
15Z
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Summary

• Assimilating Doppler velocities into model
  initial field can improve the mesoscale
  dynamical structure of initial field.
• Rain water content derived from Radar
  reflectivity is used to modify terminal velocity
  of raindrop through the assimilation processes.
• Assimilation of Doppler velocities has a positive
  impact on the simulation of the movement and
  intensity change of rainband accompanied with
  this hailstorm.

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END
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Thank You
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Sensitivity Run
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Observation of Rain Drop Distrometer dBZ - qr
Relations
The higher reflectivity has broader range of LWC.
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Result of Simulation
Just can simulate the north cell and early about
34 hours.
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Typhoon Case

• Typhoon AERE - 2004/08/23 18Z

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