Detecting Ash Clouds in Tropical Atmospheres

There is a strong dependence of the effect of water vapor on the optical depth of a volcanic ash cloud: lower, thinner clouds transmitting more of the contribution of radiance from the underlying surface are more strongly affected than higher, thicker clouds where the surface contribution is less significant. This discovery has significant ramifications in terms of ash cloud detection and tracking: (1) Beginning states of volcanic eruptive activity are relatively independent of conditions in the atmosphere, and (2) volcanic ash clouds in tropical atmospheres will be come less detectable more rapidly as the signal from the water vapor swamps the negative brightness temperature difference signal. This paper discusses a forward model that has been developed that calculates the effects water vapor has on the 'split-window' ash signal using a combination of a Mie-scattering code embedded in a MODTRAN-based atmosphere.

• Corporate Authors:

  Federal Coordinator, Meteorological Services & Support Research

  8455 Colesville Road, Suite 1500
  Silver Spring, MD  United States  20901
• Authors:
  • Watson, I M
  • Rose, W I
  • Bluth, G JS
• Conference:
  • 2nd International Conference on Volcanic Ash and Aviation Safety
  • Location: Alexandria, Virginia
  • Date: 2004-6-21 to 2004-6-24
• Publication Date: 2004-11

Language

• English

Media Info

• Media Type: Print
• Features: Figures; References;
• Pagination: 4p
• Monograph Title: Proceedings of the 2nd International Conference on Volcanic Ash and Aviation Safety, June 21-24, 2004, Alexandria, Virginia

Subject/Index Terms

• TRT Terms: Atmosphere; Aviation safety; Clouds; Depth; Detection and identification; Optics; Tropics; Volcanic ash; Volcanic eruptions; Water vapor
• Uncontrolled Terms: Mie-scattering code
• Subject Areas: Aviation; Safety and Human Factors;

Filing Info

• Accession Number: 01000862
• Record Type: Publication
• Files: TRIS
• Created Date: Jun 14 2005 12:52PM