Volcanic cloud encounters by aircraft have become more common in recent years (Casadevall, 1994; Casadevall and Krohn, 1995; Casadevall et al, 1996) and awareness of the need to mitigate such encounters has been heightened by increased air traffic in the circumpacific region where earth's volcanoes are concentrated. The most serious effects of aircraft/volcanic cloud encounters results from volcanic ash (Rose, 1986) which is distributed into jet flight levels by approximately 15 +/- 8 volcanoes every year (Miller and Kirianov, 1996). Radar systems on board jet aircraft cannot detect volcanic clouds because of the small size of volcanic ash particles, and the visual detection of these clouds by flight crews may be difficult, especially in poor visibility or at night. The problem is exacerbated by the fact that there are many hundreds of potentially active volcanoes that could threaten major air routes (especially in the N and W Pacific regions); most are not monitored and they can erupt very sporadically and without warning. Once an eruption is confirmed its volcanic cloud dispersal can be predicted with trajectory models which are based on forecasted global wind fields (Heffter and Stunder, 1993; Amours, 1994).
Two satellite-based systems can detect volcanic clouds: 1. In the ultraviolet spectrum, the Total Ozone Mapping Spectrometer (TOMS) detects SO2 gas and collects volcanic cloud position data globally about once each day (Krueger et al, 1995) during daylight hours only. 2. Infrared detectors aboard geostationary weather satellite platforms are by far the most useful volcanic cloud detectors because they detect volcanic ash directly (Rose and Schneider, 1996), and because these satellites give nearly global coverage very frequently (about every 15-60 minutes). As such they are the only robust method that can be used to systematically track volcanic clouds. The two-band thermal infrared algorithm (Prata, 1989; Wen and Rose, 1994) for volcanic cloud detection has been applied to a number of different eruptions demonstrating that it works well for a variety of different types of volcanic activity. The development of a retrieval method to obtain the mass of ash in a drifting volcanic cloud as well as its position has greatly expanded the utility of the two band infrared method because it gives us the ability to measure the mass of hazardous silicates as the clouds dissipate.
Balderson, D., 1993, Assuring Aviation Safety after Volcanic Eruptions, FAA Special Review, March 1993, 35pp plus appendices.
Casadevall, T. J., 1994, Volcanic Ash and Aviation Safety, U. S. Geol. Survey Bull 2047:1-6.
Casadevall, T. J., and M. D. Krohn, 1995, Effects of the 1992 Crater Peak eruptions on airports and aviation operations in the United States and Canada, U. S. Geol. Survey Bull 2139: 205-220.
D`Amours, R., 1994, Current and future capabilities in forecasting the trajectories, transport and dispersion of volcanic ash clouds, U. S. Geol Survey Bull 2047: 325-332.
Heffter, J. L. and B. J. B. Stunder, 1993, Volcanic ash forecast transport and dispersion (VAFTAD) model, Weather. Forecasting. 8: 533-541.
Krueger, A. J., L. S. Walter, P. K. Bhartia, C. C. Schnetzler, N. A. Krotkov, I. Sprod and G. J. S. Bluth, 1995, Volcanic sulfur dioxide measurements from the total ozone mapping spectrometer instruments, J. Geophys. Res., 100:14057-14076.
Miller, T. P. and V. Y. Kirianov, 1996, Mitigation of volcanic ash hazards to aircraft across the North Pacific, Abstracts for the Pan Pacific Hazards Conference and Trade Show, p. 174.
Rose, W. I. and D. J. Schneider, 1996, Satellite images offer aircraft protection from volcanic ash clouds, EOS, 77: 529-532
Rose, W. I., 1986, Interaction of aircraft and explosive eruption clouds: a volcanologist's perspective, AIAA Journal 25: 52-58.
Schneider, D. J., W. I. Rose and L. Kelley, 1995, Tracking of 1992 eruption clouds from Crater Peak/Spurr Volcano using AVHRR, U. S. Geol. Surv. Bull. 2139: 27-36.
Wen, S. and W. I. Rose, 1994, Retrieval of Particle sizes and masses in volcanic clouds using AVHRR bands 4 and 5, J. Geophys. Res., 99:5421-5431.
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