Computer Modeling Laboratory 11

Written report due: 2 December

Lidar remote sensing. CALIPSO and CloudSat cloud products.

Related material:
Lectures 14, 15
CALIOP ATBD, Part 3: Scene Classification Algorithms
CloudSat Level 2 Cloud Scenario Classification



Inferring extinction (optical depth) profiles from Mie lidar measurements requires an assumption on the extinction-to-backscattering ratio (called lidar ratio).
1) Table from Anderson et al. summarizes various measurements of aerosol lidar ratio (denoted S). Does an aerosol extinction-to-backscattering ratio uniquely define the type of aerosols? Briefly explain why not.
2) Calculate the lidar ratio for the molecular (Rayleigh) atmosphere and compare to the above lidar ratios of aerosols. Briefly explain your results.
3) Briefly discuss how uncertainties in the lidar ratio can affect retrievals of the aerosol optical depth from lidar observations.


The A-Train constellation provides a unique capability for studying clouds by means of passive and active remote sensing. In this task you will analyze cloud products retrieved from the CloudSat radar and CALIPSO lidar using Giovanni
On Giovanni site, select date 1 April 2008. On a map select (click on) an orbit track passing over the cloud system across the equator (near West Africa). In Curtains box and Cloud, select CALIPSO Vertical Feature mask and CloudSat Cloud Scenario. Make plots of these products by clicking on Generate Visualization. Save your plots (and/or data) (see under Visualization Results).

  1. Using your plots as an example, discuss the differences between CloudSat and CALIPSO cloud identification (refer to ATBD CloudSat (pp.4-13 and fig.13) and ATBD CALIPSO (p.8, sections 5 and 6). NOTE: Copies of both ATBDs are provided above.
  2. Classification of clouds from passive remote sensing is based on the optical depth-pressure dependence (see Figure on p.15 of Lecture 13). Briefly explain why this approach cannot be applied to CloudSat and CALIPSO.
  3. CALIPSO plot identifies the presence of aerosols. Briefly explain why there is no aerosol in the CloudSat plot (i.e., why CloudSat does not "see" aerosol).