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Work Package 2 – Overview of instrumentation, data gathering and calibration issues

Work Package 2 – Overview of instrumentation, data gathering and calibration issues. Reflectivity of Stratocumulus. Ewan O’Connor, Anthony Illingworth and Robin Hogan. Progress meeting 3 –Reading – 24-25 Oct 2002. Sensitivity.

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Work Package 2 – Overview of instrumentation, data gathering and calibration issues

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  1. Work Package 2 – Overview of instrumentation, data gathering and calibration issues Reflectivity of Stratocumulus Ewan O’Connor, Anthony Illingworth and Robin Hogan Progress meeting 3 –Reading – 24-25 Oct 2002

  2. Sensitivity Radar dominated by a few large drizzle droplets. 94 GHz can see cloud droplets but if sensitivity is reduced only drizzle can be detected. Lidar sees all Sc as sensitive to the large number of small cloud droplets

  3. Typical profiles Lidar profiles Radar profiles Drizzle free Drizzle

  4. Drizzle selection method Case – no drizzle Lidar and radar cloud base agree reasonably well If radar not sensitive enough then radar cloud base may appear above lidar cloud base. No significant radar reflectivity below cloud base. Cloud base

  5. Drizzle selection method Case – drizzle Cloud top a Radar reflectivity >-30dBZ 2 gates below lidar cloud base. If no radar reflectivity below cloud base but Z(a)<Z(b) then reflectivity still dominated by drizzle. b Cloud base from lidar Signal below cloud base

  6. Result of loss of sensitivity Chilbolton target categorization – radar at full sensitivity Chilbolton target categorization – radar sensitivity of –27dBZ

  7. Probability distributions from 15 months of data Cumulative probability distribution of radar reflectivity Percentage of Sc seen by radar that contains drizzle Solid line – Sc seen by lidar Dashed line – Sc seen by radar only In Stephens et al., 2002

  8. Current sensitivity Galileo 94 GHz radar Calibration: -10dB? <-50dBZ@1km <-44dBZ@2km

  9. Current sensitivity

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