Page 180 - Geosystems An Introduction to Physical Geography 4th Canadian Edition
P. 180
144 part I The energy–atmosphere System
(a) Mount Pinatubo eruption, June 15, 1991. Images below track the movement of aerosols across the globe.
Map location
(b) False-colour images show aerosol optical thickness: White has the highest concentration of aerosols; yellow shows medium values; and brown lowest values. Note dust, smoke from fires, and haze in the atmosphere at the time of the eruption.
PHILIPPINES
10°N
(c) Aerosol layer circles the entire globe 21 days after the eruption.
(d) The effects of the eruption cover 42% of the globe after 2 months.
▲Figure 6.1 Atmospheric effects of the Mount Pinatubo volcanic eruption and global winds. [(a) USgS. (b–d) aOT images from the advanced very high resolution radiometer (aVHrr) instrument aboard NOAA-11; neSDiS/nOaa.]
The 1991 eruption in the Philippines of Mount Pinatubo, after 635 years of dormancy, provided a unique opportunity to assess the dynamics of atmospheric circulation using satellite monitoring and tracking of contaminants from the volcanic explosion (Figure 6.1a). The Mount Pinatubo event had tremen dous impact, lofting 13 to 18 million tonnes of ash, dust,
LAOS CAMBODIA
20°N
Philippine Luzon Sea
15°N
0
250 500 KILOMETRES
CHINA
Tropic of Cancer
VIETNAM
South China Sea
Mt. Pinatubo
Manila
BRUNEI 5°N MALAYSIA Celebes
105°E 110°E 120°E Sea 125°E Equator INDONESIA
and sulfur dioxide (SO2) into the atmosphere. As the sulfur dioxide rose into the stratosphere, it quickly formed sulfuric acid (H2SO4) aerosols, which concentrated at an altitude of 16–25 km.
In Figure 6.1b, which shows atmo spheric aerosols in the first few days after the eruption, we see some of the millions of tonnes of dust from Afri can soils that cross the Atlantic each year, borne by the winds of atmo spheric circulation. We also see the effects of smoke from Kuwaiti oil well fires set during the first Persian Gulf War, as well as smoke from forest fires in Siberia and haze off the East Coast of North America.
Figures 6.1c and d show Mount Pinatubo’s aerosols mixed with air borne debris from dust storms, fires, and industrial haze as global winds swept them around Earth. This debris increased atmospheric albedo about 1.5%. Some 60 days after the eruption,
the aerosol cloud covered about 42% of the globe, from 20° S to 30° N. For almost 2 years, colourful sunrises and sunsets and a small temporary lowering of average tem peratures followed.
Aerosols move freely throughout Earth’s atmosphere, unconfined by political borders. International concerns about transboundary air pollution and nuclear weap ons testing illustrate how the fluid movement of the at mosphere links humanity more than perhaps any other natural or cultural factor. The global spread of lowlevel radioactive contamination from Japan’s nuclear disaster associated with the earthquake and tsunami in 2011 is an other example of this linkage. More than any other Earth
0°
