Air Pollution Climatology Analysis

Background

The purpose of this component of the study is to provide a historical air quality and climatological context in which the results of the emissions modeling can be evaluated. In effect, our work will help establish the regional synoptic weather patterns wherein emissions from burning in the Flint Hills can accumulate in the three urban air sheds at concentrations that are detrimental to human health. A review of previous research on climatic aspects of air pollution episodes indicates that analysis of air masses and air mass trajectories have been the most common approaches. In some of these studies, long-term climatological data are first assembled and analyzed; then the analysis looks at those specific air mass types that can be associated with the offending air pollution events. Other case study modeling efforts identify an offensive air pollution date and then use regional scale atmospheric modeling to identify a “backward air mass trajectory” that links the urban air pollution with locations of the fires that have contributed additional pollutants to the airstream and airshed.

Methods

Year 1 activities will include both development of air pollution time histories for Omaha, Kansas City, and Tulsa and then a synoptic climatology analysis for the three cities. Daily data on air pollution at each of the three cities will be analyzed to identify both background levels of air pollution and days (events) when air pollution levels exceed selected thresholds. It is common is applied climate work to examine a long time history of data to obtain both background levels and to identify times when the data ‘spike' due to some change in local conditions (such as when higher levels of ozone or PM2.5 impact the area). These few days with higher pollution concentrations skew the data positively. The statistical analysis will involve determination of daily, monthly, seasonal, and annual descriptive statistics. The emphasis will include measures of central tendency, dispersion, and skewness, and the frequency, magnitude, and seasonal timing of spikes in the data record.

During Year 1, data for the Spatial Synoptic Classification (SSC) for Omaha [1948-2005], Kansas City [1973-2005], and Tulsa [1948-2005] will also be analyzed. The SSC is an established method for determining air mass types on a daily basis and the needed data were obtained from Dr. Scott Sheridan at Kent State University, who maintains an on-line resource and updates the SSC for a number of cities across the US. Data for Topeka have been summarized (Fig. 10)

During a Flint Hills grassfire-induced pollution event in April, 2003, a dry tropical (DT) air mass moved into the Topeka area on April 11th and the air mass continued to influence air movement in the region through the 14th. The climatological summary helps document that the DT air masses associated with April 2003 event occur only about 10.7 percent of the time.

Numerous studies, have documented the utility of the SSC in heat/health watch and warning system development and in other bioclimatic research. The SSC data for Omaha, Kansas City, and Tulsa will be analyzed during Year 1 to provide daily, monthly, and seasonal frequencies of the different synoptic weather types. In year 2, periods of varying air pollution levels at these three urban locations will be matched with a daily synoptic climate type.

In addition, an attempt will be made beginning in Year 1 to determine when spring Flint Hills grassland burns have been performed for the past several years. While no formal database exists on the activities of private citizens, an attempt will be made to compile what information is available by talking with county extension agents, large land owners, and anyone who might keep records on when are where burning occurred.

The analyses described above will help identify specific dates when burning of Flint Hills rangelands can be linked with above background level air pollution events in either Omaha, Kansas City, or Tulsa. During Year 2, the meteorological condition on these specific dates will be examined in detail with special attention to wind speeds, atmospheric instability, and air mass trajectories. Results of the synoptic weather analysis will be also used to define the meteorological conditions under which smoke-induced spikes in air quality data are most likely to occur in the three cities if large scale burning is conducted in the Flint Hills. These analyses in turn will help land managers and others identify both the conditions and the long-term probability of the conditions under which burning should be discouraged or postponed until conditions are more favorable.

Air Pollution Climatology Presentation, Presentation Text (South Dakota State University Geography Convention, 4/16/2009)