1. North Atlantic Oscillation and its Influence on Ozone in London

2. North Atlantic Oscillation

3. NAO Index Magnitude of a NAO event is categorized by and index value
The amplitude is determined such that the combined sum of the products with the corresponding pattern eigenvectors explains the maximum spatial structure of the observed height anomaly field during the month.
The amplitudes were then assembled into a continuous time series, and standardized.
Translation: The CPC takes geopotential height anomalies, averages them and assigns a value based on variation in height between two locations

4. Is NAO Important?

5. Hypothesis
The positive phase of the NAO brings stronger advection of polluted air from North America
Combined with local sources, during NAO + concentrations of Ozone should be higher in London
During NAO – phase concentrations of Ozone should be lower due to the loss of inter-hemispheric transport from North America

6. Calculations
Statistical Analysis of Ozone concentration deviations from average at London – Bloomsbury station (5-10 km NW of downtown) near the British Museum.
Correlation Analysis between NAO Index Value and Deviation

7. Results
Correlation O3 Dev and NAO Index
0.33
Correlation O3 Dev and NAO + Events
0.22
Correlation O3 Dev and NAO - Events
0.06
With a significance level of α = .01, the calculated correlation coefficients for row 1 and 2 are greater than the critical value and are hence significant
NAO (-) phase correlation fall short

10. Conclusions
Correlation between O3 concentrations and NAO Index is present however only strong correlation is with NAO positive events
Strong advection into British Isles most likely brings polluted air from the North American coast during NAO positive phase
NAO negative phase demonstrates lower O3 concentrations, however more stagnant air may allow for local sources of O3 to build up
Variations in meteorology may be the cause for many of the deviations from expected correlation

11. Trouble Brewing? Trend of increasing values of NAO index
What will this suggest for future air quality in the British Isles?