"Identifying QBO and Seasonal Variations in Stratospheric Chemical Species using UARS HALOE Data"

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Sunday, 17 January 2010
Exhibit Hall B2 (GWCC)
John Anderson, Hampton Univ., Hampton, VA; and B. A. Crandall and N. M. Pothier

Seasonal oscillations and the quasi-biennial oscillation (QBO) are believed to have a substantial impact on global air circulation in the middle atmosphere. Therefore, identifying the strength of the oscillations with regards to location has been a major priority of middle atmospheric studies. The objective of this study was to identify and graphically reproduce trends and seasonal variability in stratospheric air composition using data retrieved from the HALOE satellite program. Using data collected by the UARS HALOE satellite from October 1991 to October 2005, we analyzed the data for chemical time trends and identified effects of the quasi-biennial oscillation (QBO) and the “tape-recorder effect” of air entering the middle atmosphere. The time trends were produced for data collected on water vapor, methane, and ozone concentrations. Using this data, we designed a twelve-term model to recreate the mean, trends, QBO, and seasonal oscillations within the data using principal component analysis (PCA) to refine the data to be used with the model. Secondly, principal components were run for the duration of the time and applied to the model to obtain the coefficients at a given pressure and latitude. These were then plotted for a chemical species; the seasonal and QBO coefficients were plotted separately using the mean as a backdrop. A root-mean-square (RMS) calculation was applied to provide a simple means of determining the relationship between the QBO and seasonal cycles, and the individual pressure and latitude bin to which the model was applied. Lastly, a residual plot was also created as means of identifying the “goodness-of-fit” of the model. From our results, it was concluded that while though the QBO is significant in lower latitudes and has a notable impact on the dispersion of chemical species, the seasonal cycle generally dominates upper latitudes and tends to have a stronger variation than the QBO cycle. Large residuals indicate the model was a poor fit at the lowest altitudes for ozone and water vapor, and a poor fit at the highest altitudes for methane.