Three satellite images above show a range of almost two years. The aerosol measured included crustal material as well as the sulfuric
acid and water aerosols produced by the sulfur dioxide (SO2). The blue represent small optical thickness of the order of 10-3 or less;
whereas, the reds and pinks large optical depths of the order of 10-1 or greater. Figure(left) is data taken from April 15, 1991 to May 25,
1991 which is approximately two weeks before the Mount Pinatubo eruption. The optical depth during this time interval was
consistently low throughout the globe. Figure (middle) shows optical depth from June 14, 1991 to July 26, 1991. As indicated by the
red and pink stripe around the equatorial region of the earth, the optical depth had increased significantly and exclusively in the tropics
from the Mount Pinatubo eruption. The right-figure shows the optical depth from February 2, 1993 to March 26, 1993 (over a 1.5 years
following the eruption). Globally, the optical depth had significantly thickened over the entire the Earth. The equatorial optical depth
had slightly decreased but was still well above the levels before the Mount Pinatubo eruption. The greatest increases occurred near
the poles where some pink regions were present.
平流層的溫度分布與臭氧有關。下列化學作用在平流層中不斷發生:
(a): O2 + O + M = O3 + M
(b): O3 + hv = O2 + O
作用(a)由O2、O、M (催化劑)三體碰撞產生臭氧。臭氧是極端不穩定的氣體,容易吸收
紫外線分解成O2、 O。(a)、(b)兩種作用不斷進行,其結果是化學成份不變,大氣卻因
此吸收了許多能量,提高溫度。此一過程在高度約50 公里處最有效率,因此該處溫度
最高。臭氧含量最大的地方,約在20∼30 公里之間。為什麼最高溫在50 公里處?因為
高度太高,氣體密度小,不易產生三體碰撞;高度太低則紫外線多已被吸收,而且O 原
子含量太低(O 的產生:O2 + hv = 2O,吸收非常短波長輻射,且發生在高層大氣,上述
反應不易進行。)