An assessment of HOx chemistry in the tropical Pacific boundary layer : Comparison of model simulations with observations recorded during PEM tropics A

• Published in: Journal of atmospheric chemistry 2001-03, Vol.38 (3), p.317-344
• Main Authors: CHEN, G, DAVIS, D, BARRICK, J, ANDERSON, B, BLAKE, D, BRADSHAW, J, SANDHOLM, S, CARROLL, M, ALBERCOOK, G, CLARKE, A, CRAWFORD, J, HEIKES, B, O'SULLIVAN, D, LEE, M, EISELE, F, MAULDIN, L, TANNER, D, COLLINS, J
• Format: Article
• Language: English
• Subjects: Boundary layer; Boundary layers; Chemical composition and interactions. Ionic interactions and processes; Chemistry; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; Simulation; Tropical environments
• ISSN: 0167-7764; 1573-0662
• DOI: 10.1023/A:1006402626288

Reported are the results from a comparison of OH,H^sub 2^O^sub 2^CH^sub 3^OOH, and O^sub 3^ observationswithmodel predictions based on current HO^sub x^-CH^sub 4^reaction mechanisms. The field observations are thoserecorded during the NASA GTE field program, PEM-Tropics A. The major focus ofthis paper is on thosedata generated on the NASA P-3B aircraft during a mission flown in the marineboundary layer (MBL) nearChristmas Island, a site located in the central equatorial Pacific (i.e.,2° N, 157° W). Taking advantage of thestability of the southeastern trade-winds, an air parcel was sampled in aLagrangian mode over a significantfraction of a solar day. Analyses of these data revealed excellent agreementbetween model simulated andobserved OH. In addition, the model simulations reproduced the major featuresin the observed diurnalprofiles of H^sub 2^O^sub 2^ and CH^sub 3^OOH. In the case ofO^sub 3^, the model captured the key observational feature whichinvolved an early morning maximum. An examination of the MBL HO^sub x^budget indicated that the O(^sup 1^D) + H^sub 2^Oreaction is the major source of HO^sub x^ while the major sinks involveboth physical and chemical processes involving the peroxide species,H^sub 2^O^sub 2^ and CH^sub 3^OOH. Overall, the generally goodagreement between modeland observations suggests that our current understanding ofHO^sub x^-CH^sub 4^ chemistry in the tropical MBL isquite good; however, there remains a need to critically examine this chemistrywhen both CH^sub 2^O and HO^sub 2^are added to the species measured.[PUBLICATION ABSTRACT]