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Numerical Simulations and Diagnostic Studies Relating Meteorology to Atmospheric Chemistry During TRACE-P

A Research Project for the Office of Earth Science National Aeronautics and Space Administration

The Transport and Chemical Evolution over the Pacific (TRACE-P) experiment was conducted over the western Pacific Ocean during March-April 2001. TRACE-P was a component of the NASA's Global Tropospheric Experiment (GTE). TRACE-P follows two previous missions conducted in the region during 1991 and 1994 (the Pacific Exploratory Missions--West A and B, respectively). Since those earlier missions, there has been increased interest in the origin, chemistry, and fate of the pollution plume emerging from Asia. Although the Pacific Basin is less impacted by human activities than some other parts of the world, the area is growing rapidly in both population and economic activity. TRACE-P had two scientific objectives: 1) determine the chemical composition of Asian outflow over the western Pacific during spring, and 2) determine the chemical evolution of this Asian outflow as it is transported by the atmosphere.

Meteorological conditions greatly influence concentrations and distributions of aerosols and atmospheric chemical species, and Florida State University conducted a series of research tasks to investigate and characterize the meteorological conditions during TRACE-P. Our TRACE-P research is virtually complete.

Our participation in TRACE-P had three major components:

Mission Meteorologist

Prof. Fuelberg was Mission Meteorologist on the DC-8 aircraft during TRACE-P. As such, he was responsible for meteorological forecasting for flight operations and for providing input on the origins and destinations of air parcels encountered during the flights. He coordinated with the other TRACE-P meteorologists and sought advice from local meteorologists at the various field sites. Prof. Fuelberg was a Mission Meteorologist on four previous DC-8 missions--TRACE-A (1992), PEM-Tropics A (DC-8, 1996), SONEX (SASS Ozone and NOx Experiment, 1997), and PEM-Tropics B (DC-8, 1999).

As part of being a Mission Meteorologist, we prepared meteorological products that were needed in forecasting and sent those products to the field sites. For example, Florida State prepared backward trajectories that arrived at various locations along the proposed flight tracks.

At the end of the TRACE-P analysis period, we prepared a journal manuscript describing meteorological conditions during the period. We also assisted the various TRACE-P chemists in incorporating meteorological considerations into their studies.

Intercomparison of Chemical Transport Models

This research constituted the M.S. thesis research for Chris Kiley. We intercompared four global scale and three regional scale chemical transport models during the TRACE-P Experiment. Model simulated and measured CO were statistically analyzed along aircraft flight tracks. Results for the combination of eleven flights show an overall negative bias in simulated CO. Biases are most pronounced during large CO events. Statistical agreements vary greatly among the individual flights. Those flights with the greatest range of CO value tend to be the worst simulated. However, for each given flight, the models generally provide similiar relative results. The models exhibit difficulties simulating intense CO plumes. CO error is found to be greatest in the lower troposphere. Convective mass flux is shown to be very important, particularly near emissions source regions. Occasionally meteorological lift associated with excessive model-calculated mass fluxes leads to an overestimation of mid- and upper- tropospheric mixing ratios. Planetary Boundary Layer (PBL) depth is found to play an important role in simulating intense CO plumes. PBL depth is shown to cap plumes, confining heaving pollution to the very lowest levels.

Atmospheric Transport by Wave Cyclones

This was the Ph.D. dissertation research of John Hannan. We investigated transport of boundary layer air to the free troposphere by cyclones during the TRACE-P experiment. Airstreams responsible for boundary layer venting are diagnosed using results from a high-resolution meteorological model (MM5) together with in situ and remotely sensed chemical data. Hourly wind data from the MM5 are used to calculate 3-D grids of backward air trajectories. A reverse domain filling (RDF) technique then is employed to examine the characteristics of airstreams over the computational domain, and to isolate airstreams ascending from the boundary layer to the free troposphere during the previous 36-hours. Two cases are examined in detail. Results show that airstreams responsible for venting the boundary layer differ considerably from those described by classic conceptual models and in the recent literature. In addition, airstreams sampled by the TRACE-P aircraft are found to exhibit large variability in chemical concentrations. This variability is due to differences in the boundary layer histories of individual airstreams with respect to anthropogenic sources over continental Asia and Japan. Complex interactions between successive wave cyclones also are found to be important in determining the chemical composition of the airstreams. Particularly important is the process of post-cold frontal boundary layer air being rapidly transported offshore and recirculated into ascending airstreams of upstream cyclones.

Graduate Student on this Project

Chris Kiley

Click here to view the Trace-P Post Meteorological and Trajectory Products.

Click here to reach NASA's web site for the TRACE-P Experiment.

last updated July 9, 2006