changes to the instrument synergy target categorization product
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Changes to the Instrument Synergy/ Target Categorization product. Robin Hogan Ewan O’Connor. Overview of changes. Melting layer identification using Doppler velocity Previously used only model wet-bulb temperature Melting bit in “category_bits” variable is now used

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overview of changes
Overview of changes
  • Melting layer identification using Doppler velocity
    • Previously used only model wet-bulb temperature
    • Melting bit in “category_bits” variable is now used
  • Sensitivity and error variables
    • Notably Z_sensitivity and lwp_error
  • Will work without rain gauge data
    • Uses radar for rain detection
  • Microwave brightness temperatures if available
    • Enables LWP to be recalculated using better algorithm if required
  • Lidar molecular scattering bit for visible lidars
    • Enables molecular to be used to estimate optical depth in some studies
    • Lidar beam divergence and field of view now held as variables
  • Works with ARM data
    • Tested on SGP and NSA data so far
  • Documentation!
    • http://www.met.rdg.ac.uk/radar/doc/categorization.html
melting layer identification
Melting layer identification
  • Previously rain was often diagnosed as ice because the melting layer height was taken purely from the model wet-bulb temperature
melting layer identification1
Melting layer identification

v

Z

  • Look within 5ºC of Tw=0ºC isotherm in model
    • Melting layer is where greatest divergence in radar Doppler velocity

Divergence

Classification

Melting ice

radar sensitivity
Radar sensitivity
  • Z_sensitivity variable is estimated as a function of height
    • Includes range-squared law, mean gas attenuation and ground clutter
    • Used for iwc_sensitivity and to modify model cloud fraction
  • Currently susceptible to erroneous Z values below the real radar sensitivity

Z_sensitivity

A day of Z values

1 year of cloudnet data
1 year of CloudNet data
  • PDF of dissipation rate for different types of cloud
  • Note that aircraft measurements have lower limit of detectability of ~10–6 due to aircraft vibrations

Previous range for cirrus found from aircraft

Bouniol, Hogan and Illingworth (2004)

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