Some Practical Things to learn:
Time Zones and Universal time. We use UT for satellite data because it usually spans different time zones. In the case of the Spurr eruptions the local time is Alaska Daylight Time which is 8 hours earlier than UT. For more about time around the world, have a look at this.
Latitude and Longitude of some key points:
Crater Peak, Spurr volcano: 152° 14' W 61° 16' N
Anchorage: 150° 01' W 61° 10' N
Juneau: 134° 33' W 58° 21' N
Seattle: 122° 18' W 47° 33' N
Eruption characteristics and environmental conditions, Crater Peak eruptions of Mount Spurr, 19 August 1992.
from McNutt et al, 1995, p. 165;
Start time: 0042 UT
Eruption peak: 0055 UT
End time: 0410 UT
Duration: 208 minutes
from Rose et al, 1995a, p. 21; Neal et al, 1995, p. 68; Sparks et al, 1997, p.118;
Mean Column height, 11.8 km asl
Max Column height, 13.7 km asl
Mean Eruption rate, 1120 m3/s
Max Eruption rate, 2330 m3/s
Clast density, 1500-1550 kg/m3
Fallout Volume, 14 x 106 m3 Dense Rock Equivalent
Data from NWS balloon data, Anchorage airport, 0000 UT 19 August 1992
Wind speed, 0-3 km asl, 6.5 m/s
Wind speed, 3-6 km asl, 12.3 m/s
Wind speed, 6-9 km asl, 18.6 m/s
Wind speed, 9-12 km asl, 24.9 m/s
Wind speed, 12-15 km asl, 10.9 m/s
Avg wind direction, 0-3 km 205
Avg wind direction, 3-6 km 290
Avg wind direction, 6-9 km 315
Avg wind direction, 9-12 km 308
Avg wind direction, 12-15 km 275
Tropopause height, 10.7 km asl
Temp, 0 km asl, 15.2 C
Temp, 3 km asl, -7.2 C
Temp, 6 km asl, -23 C
Temp, 9 km asl, -47 C
Temp, 12 km asl, -62.3 C
Dew Point, 0 km, 8.0 C
Dew Point, 3 km, -8.3 C
Dew Point, 6 km, -34 C
The real lab work starts here!
Signing on to Terascan:
Terascan Software functions you should test drive:
First, load some data:
Second, explore the use of some key functions:
Third, try using some more of the functions under the Tools box at the upper left.
OK, now load several more data sets as follows:
note: these number correspond to AVHRR satellite data for about 19 hours, with those numbers reprenting the UT of the satellite pass over the volcanic cloud. The last file is raw, unregistered data at 1857 UT.
Mapping and Gridding of Satellite data: This is very important because satellites view a curved surface of the earth, so mapping that surface accurately is a vital part of the process. In the data set we look at we warp the data to a map projection, in this case lambert azimuthal, which is easy to measure distance on. You should compare unwarped swath data (no .reg suffix), with the registered ones, to get an idea of the degree of warping that is needed. This is why we load the last image set, one that is raw, showing what the satellite actually sees. How does it compare with the warped image we actually work with?
Ok now you know enough to be barely able to work---so let's work.
The eruption started at 00:42 UT on 19 August and ended at 04:10 UT the same day (see table above).
Some questions for you to answer.
Given the temperature profile of the atmosphere (see balloon data above) , and the temperature of the clouds during the first few hours, how high were the volcanic clouds? (this assumes that the clouds are cooled to the same temperature as the air that surrounds them) (you can compare your answer with data that came from observations during the eruption--see table above)
How fast is the volcanic cloud expanding downwind? (You can measure this using the survey tool)
How fast is the cloud spreading across (perpendicular to) the wind?
When did the cloud reach Anchorage? Juneau? (note lat and long info for those places, above)
Does the wind data make sense, given the height estimate and the rate of movement of the cloud? (see balloon data again)
This exercise has shown you some basic data and tools. Is is meant as a hands-on introduction to the data from only one satellite system. We have learned to use satellite data for many purposes.
The Spurr remote sensing results that you have worked on are shown for you in this web source. Discussion of volcanic cloud results from a variety of eruptions can be found in our web resources also. A new example, the Feb 2000 eruption of Hekla, Iceland is discussed here.
Still want to learn more about this? Volcanic clouds web page.
http://www.DOMAIN/PATHNAME.HTM -- Revised: 13 SEPTEMBER 2000
Copyright © 2000 MTU Department of Geological Engineering and Sciences. All Rights Reserved.