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Weekly cycles of air pollutants, precipitation and tropical cyclones in the coastal NW Atlantic region

  • An Erratum to this article was published on 24 September 1998


Direct human influences on climate have been detected at local scales, such as urban temperature increases and precipitation enhancement1,2,3, and at global scales4,5. A possible indication of an anthropogenic effect on regional climate is by identification of equivalent weekly cycles in climate and pollution variables. Weekly cycles have been observed in both global surface temperature6 and local pollution7 data sets. Here we describe statistical analyses that reveal weekly cycles in three independent regional-scale coastal Atlantic data sets: lower-troposphere pollution, precipitation and tropical cyclones. Three atmospheric monitoring stations record minimum concentrations of ozone and carbon monoxide early in the week, while highest concentrations are observed later in the week. This air-pollution cycle corresponds to observed weekly variability in regional rainfall and tropical cyclones. Specifically, satellite-based precipitation estimates indicate that near-coastal ocean areas receive significantly more precipitation at weekends than on weekdays. Near-coastal tropical cyclones have, on average, significantly weaker surface winds, higher surface pressure and higher frequency at weekends. Although our statistical findings limit the identification of cause–effect relationships, we advance the hypothesis that the thermal influence of pollution-derived aerosols on storms may drive these weekly climate cycles.

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We thank D. Parrish for the Canadian pollution data, S. J. Oltmans for the Bermuda ozone data, C. Landsea for the tropical cyclone database, and R. Spencer for the MSU daily precipitation data set.

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Correspondence to Randall S. Cerveny.

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Figure 1: Location map.
Figure 2: Mean values of three variables by day of the week; error bars show standard error of the mean (±1σ).


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