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At least 1,063 records · Page 59
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NASA NTRS1993

Implication of the January 1990 Volcanic Eruption on Io for Resurfacing Rates and Energetics

The high temperature event observed by ground based infrared radiometry of Io in January of 1990 can be modeled as an extremely active silicate lava flow which increased its area and cooled over a period of three hours. The best model at the start of the observations is a thermal source at 1200 K with an area equal to that of a circle of 5.6 km radius, while at the end of the observation sequence a source with a temperature of 700 K and a 13 km radium provides the best match. Given a flow thickness of 10 m, this implies an eruption rate of 300,000 cubic meters per second. This is large by terrestrial standards but consistent with estimates of lunar eruption rates (Head and Wilson 1981) and some terrestrial eruptions such as the 1800-1801 Hualalai flow in Hawaii (Baloga and Spudis 1992)...

Johnson, T. V.↗
NASA NTRS2008

SAGE II Measurements of Stratospheric Aerosol Properties at Non-Volcanic Levels

Since 2000, stratospheric aerosol levels have been relatively stable and at the lowest levels observed in the historical record. Given the challenges of making satellite measurements of aerosol properties at these levels, we have performed a study of the sensitivity of the product to the major components of the processing algorithm used in the production of SAGE II aerosol extinction measurements and the retrieval process that produces the operational surface area density (SAD) product. We find that the aerosol extinction measurements, particularly at 1020 nm, remain robust and reliable at the observed aerosol levels. On the other hand, during background periods, the SAD operational product has an uncertainty of at least a factor of 2 during due to the lack of sensitivity to particles with radii less than 100 nm.

Thomason, Larry W.↗
NASA NTRS2008

CALIPSO Observations of Volcanic Aerosol in the Stratosphere

In the stratosphere, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) has observed the presence of aerosol plumes associated with the eruptions several volcanoes including Montserrat (May 2006), Chaiten (May 2008), and Kasatochi (August 2008). While the dense ash plumes from these eruptions dissipate relatively quickly, CALIPSO continued to detect an enhanced aerosol layer from the Montserrat eruption from the initial observations in June 2006 well into 2008. Solar occultation missions were uniquely capable of monitoring stratospheric aerosol. However, since the end of long-lived instruments like the Stratospheric Aerosol and Gas Experiment (SAGE II), there has been no clear space-based successor instrument. A number of active instruments, some employing new techniques, are being evaluated as candidate sources of stratospheric aerosol data. Herein, we examine suitability of the CALIPSO 532-nm aerosol backscatter coefficient measurements.

Thomason, Larry W.↗