Tropospheric Methane Over the Pacific Basin During TRACE-P

We received funding for the acquisition, statistical analysis, interpretation, and publication of atmospheric methane data collected during the Transport and Chemical Evolution over the Pacific (TRACE-P) mission, flown February through April of 2001. These high precision measurements were made aboard the NASA DC-8 and P-3B aircraft using a fast response, tunable diode laser system, the DACOM instrument. Our analysis focused on the vertical and geographical distribution of this key trace gas, particularly in the context of other data available from the region such as those from the Pacific NOAA CMDL surface sites, and earlier NASA aircraft missions (such as PEM-West A and B). The paper reporting these results, "Large-Scale Distribution of CH4 in the Western Pacific: Sources and Transport from the Asian Continent" by authors K.B. Bartlett, G.W. Sachse, T. Slate, C. Harward, and D.R. Blake, is attached. The dataset of roughly 13,800 CH4 measurements ranged between 1602 ppb in stratospherically impacted air and 2149 ppb in highly polluted air. Overall, we found that CH4 concentrations were highly correlated with trace gases characteristic of a mix of anthropogenic industrial and combustion sources. They were strikingly correlated with ethane (C2H6) in particular, whose major sources are natural gas leakage and biomass burning. Correlation between the two hydrocarbons indicated that these sources may dominate for CH4 as well at this time.