1. PHY Lecture 16
Lidar remote sensing

2. LIDAR backscatter instrument
From Tom Duck, Atmospheric Optics Lab, Dalhousie
emitted
received
time

3. LIDAR backscatter instrument
aerosol properties

4. LIDAR backscatter

5. LIDAR backscatter retrieval problem
Need to relate backscatter coefficient, b, to volume extinction coefficient, s
Generally use normalised power
In differential form
Assume relationships between b and s in the form b=asb
Eg. Water cloud b~ 0.625s.
Special case is to asume db/dr=0 – particles uniformly mixed along line of sight (slope method)
General problems are 1) the b-s relationship
2) the instability of the solution due to ratio of small numbers (decreasing with range)
2s( r)

6. LIDAR backscatter profiles
(From Stephens, 1994)
Lidar backscatter from a typical marine boundary layer

7. Differential absorption LIDAR
Retrieve aerosol properties and gas number densities (NA) from extinction of beam without knowledge of relations between b and s

8. Differential absorption LIDAR

9. ESA’s Water vapour lidar expt (WALEX) 925nm DIAL

10. Space-based LIDAR - LITE

11. Space-based LIDAR - LITE

12. Space-based LIDAR - LITE
Tropical convective mulitlayer cloud systems
Saharan dust

13. Space-based LIDAR - FUTURE