Observations of ozone and related species in the northeast Pacific during the PHOBEA campaigns: 1. Ground‐based observations at Cheeka Peak

Dan Jaffe,Theodore Anderson,Jen Danielson,Donald Blake,William Simpson,David Streets,Dave Covert,Joyce Harris,Barbara Trost

doi:10.1029/2000jd900636

Abstract

As part of the Photochemical Ozone Budget of the Eastern North Pacific Atmosphere (PHOBEA) project, we made observations of CO, O3, NOx, peroxyacetyl nitrate (PAN), nonmethane hydrocarbons (NMHC), Rn, aerosol scattering, aerosol absorption, and aerosol number density during the springs of 1997 and 1998 at the Cheeka Peak Observatory (CPO) on the western tip of Washington State. The data have been segregated to quantify the mixing ratio of these species in the Pacific marine atmosphere. However, even in these marine air masses, there are occasionally substantial enhancements of NOx and aerosols, but not CO, which we attribute to diesel exhaust from ship traffic to and from major ports in the region. The marine air masses were further classified into four categories based on 10‐day back isentropic trajectories; high, mid, and low latitude and those which had crossed over the Asian industrial region. Mean marine mixing ratios in 1998 were significantly higher than the 1997 values for CO (1997 mean equal to 151, 1998 mean equal to 170 ppbv), ethane (1771, 1968 parts per trillion by volume (pptv)), and ethyne (306, 452 pptv). Also, segregation of the 1998 data by air mass origin produced smaller differences in the mixing ratios for most species when comparing different source regions. We attribute both of these results to elevated emissions associated with unusually large areas of biomass burning which took place in Indonesia and Siberia dunng late 1997 and 1998. The relative enhancements of CO, ethane, ethyne, and propane we observed at CPO are consistent with enhanced biomass burning and industrial sources in the spring of 1998, relative to the spring of 1997.

Highlights

Ozoneplaysa keyrolein tropospherichemistry.It is the gionsof theworld,mostnotablyEastAsia[Logan,1994;Lee primarysourcefor theOH radicalwhichisthemostimportant et al, 1998], due to tile continuedrapid increaseof NOx oxidantin thetroposphereI.t is alsoa greenhousgeasandhas emissions(-4%/yr) from East Asia [Akimotoand Narita, toxicandphytotoxiceffectsat levelsnot far aboveambient. 1994;Streetsand Waldhoff,2000]
Previously,we have shown that anthropogenicemissions from EastAsia canbe transportedto WashingtonStateduring springin aslittle as5 days[Jaffeet al., 1999]
Because the focus of this work is on the atmosphericchemistryof the North Pacific environment, we segregatedthe data conservativelyto consideronly periods when we were fairly certain that recentemissionsfrom North America had not impactedour observations.In this paper we will use the term "marine" to refer to air masses which have not crossedover or been influencedby North Americanemissionswithin at leastthe past3 days,and"continental"to refer to the portionof the datafor which a North Americaninfluenceis likely

Summary

Introduction

Ozoneplaysa keyrolein tropospherichemistry.It is the gionsof theworld,mostnotablyEastAsia[Logan,1994;Lee primarysourcefor theOH radicalwhichisthemostimportant et al, 1998], due to tile continuedrapid increaseof NOx oxidantin thetroposphereI.t is alsoa greenhousgeasandhas emissions(-4%/yr) from East Asia [Akimotoand Narita, toxicandphytotoxiceffectsat levelsnot far aboveambient. 1994;Streetsand Waldhoff,2000]. Because the focus of this work is on the atmosphericchemistryof the North Pacific environment, we segregatedthe data conservativelyto consideronly periods when we were fairly certain that recentemissionsfrom North America had not impactedour observations.In this paper we will use the term "marine" to refer to air masses which have not crossedover or been influencedby North Americanemissionswithin at leastthe past3 days,and"continental"to refer to the portionof the datafor which a North Americaninfluenceis likely. The median NOx mixing ratio in continentaloutflow from Asia was 120 pptv, as observedduringthe PEM-West campaignsin the springof 1994 [Kondoet el., 1997].

Results

Conclusion