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Changes to the Instrument Synergy/ Target Categorization product

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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Changes to the Instrument Synergy/ Target Categorization product

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  1. Changes to the Instrument Synergy/Target Categorization product Robin Hogan Ewan O’Connor

  2. 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

  3. Melting layer identification • Previously rain was often diagnosed as ice because the melting layer height was taken purely from the model wet-bulb temperature

  4. 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

  5. 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

  6. 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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