Open AccessPeroxy radical observations using chemical ionization mass spectrometry during TOPSE
Author(s) -
Cantrell Christopher A.,
Edwards G. D.,
Stephens S.,
Mauldin L.,
Kosciuch E.,
Zondlo M.,
Eisele F.
Publication year - 2003
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 - 10.1029/2002jd002715
Subject(s) - latitude , atmospheric sciences , altitude (triangle) , ozone , environmental science , troposphere , ionization , radical , analytical chemistry (journal) , chemistry , meteorology , environmental chemistry , geology , physics , ion , geodesy , geometry , mathematics , organic chemistry
Peroxy radicals (HO 2 + RO 2 ) were measured by chemical conversion‐chemical ionization mass spectroscopy in the TOPSE (Tropospheric Ozone Production about the Spring Equinox) campaign that took place February through May 2000. Instrumentation for these measurements was deployed on the NCAR/NSF C‐130 aircraft that flew at latitudes from 40 to 85°N, and altitudes from the surface to 7.5 km over the North American continent. The measurements demonstrate the evolution of photochemical activity as time progresses through the study period due to increases in free radical source rates. The increase in average peroxy radical concentration moves northward as the maximum solar elevation and length of sunlit days increase. HO x RO x (HO 2 + RO 2 ) concentrations are distributed lognormally with means of 11.5 and 7.8 pptv for the middle‐latitude band (MLB) and high‐latitude band (HLB), respectively. The observations agree well on average with steady state derived concentrations; measurement‐model concentration ratios are 1.04 (MLB) and 0.94 (HLB). Concentrations within a given latitude band and altitude region sometimes appear to increase with NO x concentrations, but this correlation nearly disappears at low and moderate NO x levels when the data are parsed by radical production rate; lower radical levels are observed at the highest NO x levels measured (near 1 ppbv). These data are compared with results from other recent observations utilizing a variety of platforms.