Tropospheric Modeling Studies of TRACE-P Data: Investigation of the HO_x/NO_x/O₃ Photochemical System and its Coupling to Sulfur/Aerosol Species

Georgia Institute of Technology
Doug Davis (PI), Gao Chen (Co-PI), Shaw Liu, and Mian Chin

To be carried out our model based investigations of tropospheric chemistry as related to the following questions and issues:

• What role do photochemical processes play in the western North Pacific as related to the column ozone budget? More specifically, how does the magnitude of photochemical ozone formation compare with the ozone flux from the stratosphere for this region? To what extent does the latter comparison change as one transitions from late winter through spring and what factors are responsible for this? And finally, how does Pacific Rim outflow impact on the photochemical ozone budget in the central and eastern North Pacific?

• What are the relative contributions of primary and secondary NO_x sources to the active pool of photochemical NO_x, in the western North Pacific? And, to what extent is this balance perturbed by Pacific Rim outflow?

• What are the controlling factors that dictate HO_x levels and therefore the oxidizing power in the western North Pacific? And, to what degree is Pacific rim outflow influencing these levels at remote locations in the Pacific?

• What are the relative contributions of biogenic versus anthropogenic and/or volcanic sulfur sources in the North Pacific in the production of H₂SO₄(g) and sulfate; and do these contributions change significantly as a function of distance from the northwestern Pacific rim?

• What are the chemical and physical factors controlling H₂SO₄ (g) and sulfate levels in the western North Pacific and how is this setting altered by Pacific Rim outflow.? What evidence is there for new particle formation in the form of binary nucleation versus other forms such as ternary or ion controlled nucleation? Can new particle formation occur on the fringes of continental plumes or are aerosol growth processes dominating?

• What is the degree to which mineral aerosols associated with the spring outflow influence the chemical conversion and scavenging of non-sulfur species, i.e., NOy and HOx species.

Investigation of these issues and questions will build on earlier work completed during PEM-West A and B, PEM-Tropics A as well as that from on-going analyses of PEM-Tropics B data. Data analysis will involve the use of both DC-8 and P-3B TRACE-P airborne observations. The analysis will engage several versions of a basic box model including: a time-dependent photochemical box model with and without coupling to a sulfur/aerosol chemistry module, a Lagrangian photochemical model, and an aerosol-dynamic sectional model that can be used to simulate the temporal variations in the aerosol size distributions. Interpretation of the output from these models will be supplemented with data from trajectories, satellite imagery, and ozonesonde information. It is also expected that some data will be made available from the ACE-Asia field program and that some degree of collaboration with some members of the science team will take place. Given our past collaboration with the modeling group within the Atmospheric Sciences Division at NASA Langley, we again anticipate several collaborative efforts with this group during TRACE-P.