Publication Date:
2013-08-18
Description:
[1] This paper seeks to investigate the extent to which stratosphere-to-troposphere transport (STT) impacts the Canadian Rocky Mountains foothills. Beryllium-7 ( 7 Be) was monitored weekly at Harlech, Alberta, from July 2003 to June 2004, and daily during the spring of 2004. These data, together with hourly ozone (O 3 ) and relative humidity (RH) measurements, are presented and analyzed, with a focus on the spring of 2004. A Lagrangian dispersion model was used to help determine the origin of air parcels arriving at Harlech in order to assess if these periods were related to well-defined stratospheric intrusions. The modeling results show that events consisting of above average surface observations of 7 Be and O 3 , and below average surface observations of RH, are the result of the arrival of air originating from the mid- and upper troposphere. During the spring of 2004, no direct STTs were observed; all identified events were determined to be indirect STTs or mid- to upper troposphere transport that occurred several days prior to being detected at Harlech. The most significant event occurred between April 3-11, which had the longest period of elevated 7 Be and O 3 observations and the lowest RH measured during the spring of 2004, and where the modeling showed a strong stratospheric input. This input can be connected with two well-defined stratospheric intrusions occurring over the northern Pacific, more than 5 days before the associated surface observations. Furthermore, the modeling shows that periods of below average 7 Be and O 3 occurred when the station was mainly influenced by air masses circulating in the boundary layer.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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