Photochemical Ozone Budget of the Eastern North Pacific Atmosphere-II (PHOBEA-II)


In our now completed NSF project Photochemical Ozone Budget of the Eastern North Pacific Atmosphere (PHOBEA) we investigated the chemistry of the background North Pacific atmosphere during spring using observations from the Cheeka Peak Observatory in Washington state and aircraft vertical profiles.   In PHOBEA-II, we will extend our previous investigations by making ground and airborne observations during all seasons and adding in a number of new measurements.  Our primary goal is to understand the current sources for these compounds, as well as possible future changes in composition of the air which arrives to the west coast of North America.  Specific questions to be addressed include:


1.      What is responsible for the relatively high mean spring ozone mixing ratios observed during PHOBEA (mean values of 45 ppbv at surface, 60 ppbv at 2-4 km above sea level)?

2.      To what extent does the elevated mean ozone, observed  at 2-4 km asl over the Pacific, impact surface mixing ratios in the mountainous regions of the western U.S.?

3.      Why do some long range transport events from Asia to North America have elevated ozone while others do not?

4.      What is the speciation of NOy in the eastern North Pacific atmosphere?  What fraction of NOy is due to upstream anthropogenic emissions, compared with other sources?

5.      How does precipitation impact the mixing ratios of O3 (indirectly), NOy and/or aerosols (nss-SO42-) in the eastern North Pacific atmosphere? 

6.      What is the relative contribution of industrial emissions, fires, and the stratosphere to the budgets of CO, O3, NOy and non-seasalt sulfate?

7.      How well can current global and regional models simulate the sources, transport and processing of gases and aerosols during transport from Asia to North America?


Our primary tools are ground based observations at Cheeka Peak and airborne observations from a new, low cost airborne platform, a Beechcraft Duchess aircraft.  The Duchess is being outfitted with in-situ sensors for CO, O3, aerosol scatter, temp, RH and canisters for NMHCs.  Measurements will tie in with several planned experiments in the Pacific, including the NASA TRACE-P, ACE-Asia and the NOAA-ITCT projects.  Observations will be focused on the 2001-2002 time frame with most of the work in 2003 focused on data analysis and publication.