Click on any of the questions below applicable to the Giovanni A-Train instance for further information.
- What is the A-Train?
- What data are currently available for visualization in Giovanni 3?
- What data parameters from CloudSat are available in Giovanni 3?
- How does Giovanni 3 display the A-Train data?
- How are dates and region of interest selected for the A-Train instance?
- How is the output generated for the A-Train instance?
- Why is this called a "beta" instance?
6.1 What is the A-Train?
The A-Train of satellites circles Earth in a "formation flying" configuration. Only about 16 minutes pass between the time the first satellite (Aqua) and the last (Aura) crosses the Equator. The formation is planned to be closed in 2008 with the launch of the Orbiting Carbon Observatory (OCO) that will be maneuvered in front of Aqua. Currently, this fleet of satellites stretches across 6,000 kilometers (3750 miles) in space, with each traveling about 7 kilometers per second, in a tightly controlled "box". CloudSattrails Aqua by an average of about 60 seconds, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) follows in 12 seconds, followed by Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) in 60 seconds, followed by Aura in 840 seconds (14 minutes). The satellites are NOT on the same orbital plane, even though they are close. The largest difference in their right ascention nodes is such that it results in Equatorial separation of 2 degrees (222 km) only, e.g. between MODIS nadir and CloudSat. However, MODIS nadir and the MLS science retrival practically overlap. As of 2007, CloudSat and CALPSO also overlap. Numerous details can be found on the web, e.g. from NASA Langley Research Center, and our simple A-Train Data Depot description of the ground tracks.
6.2 What data are currently available for visualizationin Giovanni 3?
Currently available for simple previewing are certain cloud, temperature, humidity, and aerosol data from the Cloud Profiling Radar (CPR) instrument on CloudSat,MODIS/Aqua, AIRS/Aqua, and CALIPSO. We are striving to constantly add new measurements characterized by these four major themes.
6.3 What data parameters from CloudSat are available in Giovanni 3?
Clouds Reflectivity(dBz) and Received Echo Powers from Cloudsat
Cloud top characteristics, and atmospheric temperature and humidityfrom MODIS and AIRS on Aqua.
Cloud and aerosol classes from CALIPSO.
Here is the current list of parameters from all instruments available for visualization.
6.4 How does Giovanni 3 display the A-Train data?
Giovanni 3 generates the data output for CloudSat as a "Curtain" and "horizontal strip" plots. A Curtain Plot creates a two-dimensional representation of data parameter values plotted against pressure or altitude (in the vertical dimension) and distance along the satellite ground track (in the horizontal dimension). The data parameter values in the Curtain Plot are displayed using a color palette. The strip plots represent collocated swaths of cloud or atmospheric column charactersitics.
6.5 How are dates and region of interest selected for the A-Train instance?
The A-Train interface consists of orbit picker, temporal selection, and parameter selection. The user initially selects the year, month, day, then updates the map, and then clicks on an orbit to select the orbital piece of interest available for the selected day. Currently, the orbit picker uses available CloudSat radar reflectivity data to draw the orbits. Hence, the data range right next to the Update Map button reflects the available temporal range and the leading edge of the CloudSat reflectivity data. However, the parameters in the parameter selection boxes are coming from various instruments, having their processing at various stages, not synchronized with CloudSat. Thus, the time range for each parameter reflects the availability of this parameter for the purposes of the A-Train mission, i.e.it reflects the availability of the CloudSat-collocated subset, rather than the original data. Hence, the starting day is relevant to the CloudSat "first light", but the leading edge is not necessarily constrained by the availability of CloudSat reflectivity data.
Concerning the region of intrest,Ascending, Descending, or Polar orbital tracks may be selected. A point on the orbital track is designated with the Java applet map, and the range along the track (with this point at the center of the range) is designated. The minimum range is 350 kilometers.
6.6 How is the output generated for the A-Train instance?
Once the date and range have been selected, the Curtain Plot can now be generated by clicking the "Run Service" button. All four parameters can be plotted together on a single output page, or individual parameters can be displayed. (To remove a parameter from the display, depress the "Ctrl" button and click on the parameter. To add a deleted parameter, click on the deleted parameter. Selected parameters will be highlighted in blue.).
6.7 Why is this called a "beta" instance?
Development of the instance and the addition of more parameters and plotting options is continuing.