Open AccessMechanisms for midlatitude ozone loss: Heterogeneous chemistry in the lowermost stratosphere?
Author(s) -
Smith Jessica B.,
Hintsa Eric J.,
Allen Norton T.,
Stimpfle Richard M.,
Anderson James G.
Publication year - 2001
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000jd900464
Subject(s) - tropopause , middle latitudes , cirrus , atmospheric sciences , stratosphere , ozone , ozone depletion , saturation (graph theory) , chlorine , chemistry , environmental science , geology , mathematics , organic chemistry , combinatorics
The question of midlatitude ozone erosion by chlorine free radical catalysis is examined. We present and analyze simultaneous, high‐resolution observations of ClO, H 2 O, tropopause height, particle reactive surface area, and ice saturation occurrence frequency obtained from the NASA ER‐2 aircraft. The objective is to test the hypothesis that the existence of cirrus clouds or cold aerosols in the first few kilometers above the tropopause at midlatitudes is responsible for increasing the ratio of chlorine free radicals to total inorganic chlorine, thus amplifying the rate of catalytic ozone destruction. The observations reveal a sharp decrease in ice saturation frequency at the tropopause, a marked degree of under‐saturation just above the tropopause, a corresponding sharp gradient in the product of cold aerosol reactive surface area and reaction probability, γ S a , and, finally, the consistent absence of enhanced concentrations of ClO immediately above the tropopause. These results suggest that midlatitude ozone loss is not controlled in situ by the mechanism of cirrus cloud and/or cold aerosol enhancement of chlorine radicals in the vicinity of the tropopause.