Background Pollution & Traffic
The results from the CO Streetbox monitors capture many of the characteristics of the site. Over night CO levels tend to be close to zero, as would be expected when the main source of pollution, the traffic, is at its minimum. During the working week two CO peaks can be identified associated with the morning and evening rush hours (which are absent at weekends). Changing synoptic conditions, which drive the in-street flows and are the source of any imported pollution, show:
- High pressure systems, with light winds (<1ms-1) and easterly flows generate high pollution episodes;
- Prevailing low pressure systems and SW winds result in more subtle differences in the distribution of pollution, depending on the obliqueness of the synoptic flow to Marylebone Rd; e.g. a strong S component (i.e. SSW) supports a flow across the top of the canyon from S to N, which generates a counter flow at ground level, sweeping the pollution from the N to the S side of Marylebone Rd; whilst
- Strong Westerly component winds support more uniform mixing throughout the cross-section of the street and hence more similar CO values on both sides of Marylebone Rd.
Background Monitoring
Supersite and Streetbox for Calibration |
Sonic and Streetbox, Site 1 |
Supersite in Front of Westminster Uni Towards Baker St |
Supersite in Front of Westminster University |
WCH Rooftop View of Intersection, Sites 1, 2 and 3 |
