Dr. Colette L. Heald presented a seminar at Colorado State Univerisity on May 22, 2006 entitled “Observing Tropospheric Composition: Insights on Sources and Fate of Pollution”
The abstract of her talk is
“Understanding the composition of the troposphere is vital to issues of air quality and climate forcing. The suite of observations of tropospheric
composition from surface sites, aircraft campaigns and remote platforms provide a means of testing current knowledge, as represented by models, and investigating the links between air quality, chemistry and climate. This talk will focus on how we can use these observations to understand the sources and fate of pollution in the troposphere, highlighting the role of satellite observations. The integration of observations has been successfully applied to estimate emissions of carbon monoxide and observe the intercontinental transport of this pollution. Understanding the formation and transport of aerosols in the troposphere represents a greater challenge. The transpacific transport of Asian sulfate has important consequences for domestic air quality objectives. Space-based observations of aerosols are used here with in situ observations to examine the evolution and impact of this transport. Recent observations aboard aircraft off of Asia show a large burden of organic carbon aerosol in the free troposphere. The inability of current models to explain this aerosol suggests an incomplete understanding of secondary organic aerosol formation, with significant implications for both air quality and climate forcing.”
A key statement in this abstract is the recognition that
“Recent observations aboard aircraft off of Asia show a large burden of organic carbon aerosol in the free troposphere. The inability of current models to explain this aerosol suggests an incomplete understanding of secondary organic aerosol formation, with significant implications for both air quality and climate forcing”.
A new paper that she has in press in the Journal of Geophysical Research provides an in depth report on her research on aerosols. The paper is
Heald, C.L., D.J. Jacob, R.J. Park, B. Alexander, T.D.Fairlie, D.A. C hu, R.M. Yantosca, Transpacific transport of Asian anthropogenic aerosols and its impact on surface air quality in the United States, J. Geophys. Res., in press , 2006.
The abstract of the paper reads,
“We use satellite (MODIS) observations of aerosol optical depths (AODs) over the North Pacific, together with surface aerosol measurements at a network of remote U.S. sites (IMPROVE), to improve understanding of the transpacific transport of Asian aerosol pollution and assess the ability of a global 3-D chemical transport model (GEOS-Chem CTM) to quantify Asian aerosol enhancements in U.S. surface air. The MODIS observations show the strongest transpacific transport occurring in spring at 40-55oN. This transport in the model takes place mainly in the lower free troposphere (900-700 hPa) because of scavenging during transport either in the boundary layer or during lifting to the upper troposphere. The preferential altitude of aerosol transpacific transport results in direct impact on the elevated terrain of the NW United States. Sulfate observations in the NW United States in spring 2001 show higher concentrations on the days of model predicted maximum Asian influence (1.04 μg m-3) than seasonal mean values (0.69 μg m-3). No such Asian enhancements are observed for nitrate or for organic carbon (OC) aerosol. Distinct Asian sulfate episodes correlated with dust events are observed in the NW United States and simulated with the model. The mean Asian pollution enhancement in that region in spring is 0.16 μg m-3 with a 50% estimated uncertainty. This is higher than the estimated natural concentration of 0.09 μg m-3 presently used as objective for regulation of visibility in U.S. wilderness areas.”
This research clearly documents the importance of the long range transport of aerosols in the climate system, as also identified in the 2005 National Research Council report in a section entitled “TELECONNECTIONS AND RADIATIVE FORCING”. This type of “teleconnection” over long distances is a first order climate effect which alters the diabatic heating of the troposphere significantly. The result of this alteration in diabatic heating are changes in large scale weather patterns (e.g. see).
A focus on the importance of these types of heterogeneous climate forcing should be a major focus of the international climate assessments (e.g.see), but unfortunately, so far has been mostly ignored since the IPCC and other assessments have made global average surface temperature the icon of climate change. Clearly based on research such as presented in the Heald et al study, the assessments are overlooking critical climate science.