Work Package 2 – Overview of instrumentation, data gathering and calibration issues Lidar Calibration Ewan O’Connor, Anthony Illingworth and Robin Hogan Progress meeting 3 –Reading – Oct 2002

Calibration technique  ’=1/2  k Use Mie theory for spherical droplets. k is constant for cloud droplets (D=8-30  m).

Multiple scattering Calculate  as a function of range using Eloranta’s model (1998). Need to know laser divergence and telescope FOV.

Aerosol k in aerosol variable  therefore extinction unknown  effect on calibration unknown Current solution: Reject profile for calibration if  a > than some predetermined value

Validation – UV Raman lidar Calibrate UV Raman lidar with molecular backscatter. To validate – need to calculate atmospheric transmission at both wavelengths and the value of  for each instrument.

Validation – UV Raman lidar Calibrate UV Raman lidarCompare calibrated CT75K ceilometer

Validation – UV Raman lidar Step 1. Calibrate both lidars Step 2. Adjust for differences in atmospheric transmission Step 3. Adjust for differences in multiple scattering

Validation in space – LITE

CT75K – solar background