Giovanni-3 Operation Technical Summary: Vertical Feature Mask Extractor

Vertical Feature Mask Extractor

The lidar instrument on-broad the Calipso platform permits the identification of a variety of atmospheric features over the entire vertical extent of atmosphere seen along the Calipso orbit track. These features are classified by general type (Aerosol, Cloud, Polar Stratospheric Cloud) and by feature sub-type (Aerosol: dust, smoke, ...; Cloud: altostratus, cirrus, ...; PSC: depolarizing aerosol, ...). The Calipso Vertical Feature Mask Extractor extracts the various atmospheric features seen along the Calipso orbit track and formats them for colored-coded display by the Curtain Plot Renderer.

Input Parameters
Calipso Vertical Feature Mask Data in Satellite Swath Format, trimmed to the length of orbit selected by the orbit picker

Output Description
 Extracted Calipso Vertical Feature Mask Data in Satellite Swath Format

Output Parameters
Same as input.

File Type
Input: HDF4
Output: HDF4

Sub-Definitions

• Center Pixel: the middle pixel along the horizontal (across-track)
  dimension of the swath 
• Orbit Arc Length: the arc length of the orbit track selected
  for data processing in kilometers.
• Orbit Picker: the orbit-based data selection tool for A-Train Giovanni-3
• Orbit Track: the segment of orbit selected for data processing
• Swath: 1- or 2-dimensional data structure, typically representing
  an array of measurements distributed along the center pixel of a
  satellite track.

Description of This Operation

1. Unpack the Calipso Vertical Feature Mask at the desired resolution,
   either five kilometer or 333 meter resolution.
   
2. Extract Vertical Feature Mask features according to the User's
   data selection criteria. This is done along the entire Calipso
   orbit track, through the entire vertical extent of the profile.
   
3. Assign a color code to the features that were extracted. This
   distinguishes features for display by the Curtain Renderer.

Algorithm Details
 IDL is used because array-based operations may be performed easily in that language.

Caveats/Warnings
- Currently, the Vertical Feature Mask extraction can only be performed at 5 km resolution.

- Sub-type feature classification is not currently provided in Calipso Vertical Feature Mask dataset.

Origin/Software
 Implemented in IDL.

For a detailed description of the Calipso Vertical Feature Mask dataset, refer to the following document:

CALIPSO Quality Statements: LIDAR Level 2 Vertical Feature Mask

This Technical Summary page is a draft version -- for information on this operation while
the document is being prepared, please send a message to GES DISC Help.