A conically scanning, continuous-wave LIDAR is placed on an island in the central Baltic Sea with large open-water fetch, providing wind and turbulence profiles up to 300 m height. LIDAR and Weather Research and Forecasting (WRF) profiles from one year are used to characterize the marine boundary layer, at the same time performing an evaluation of the WRF model against LIDAR measurements with a focus on low-level jet representation. A good agreement is found between the average wind speed profile in WRF and LIDAR, with the largest bias occurring during stable conditions. The LLJ frequency is highest in May with frequency of occurrence ranging between 18% and 27% depending on the method of detection. Most of the LLJs occur during nighttime, indicating that most of them do not have local origin. For cases with simultaneous LLJs in both data sets the WRF agrees well with the LIDAR. In many cases, however, the LLJ is misplaced in time or space in the WRF simulations compared to the LIDAR. This shows that models still must be improved to capture mesoscale effects in the coastal zone.

Streaky structures of narrow (8-9 km) high wind belts have been observed from SAR images above the Baltic Sea during stably stratified conditions with offshore winds from the southern parts of Sweden. Case studies using the WRF model and in situ aircraft observations indicate that the streaks originate from boundary layer rolls generated over the convective air above Swedish mainland, also supported by visual satellite images showing the typical signature cloud streets. The simulations indicate that the rolls are advected and maintained at least 30–80 km off the coast, in agreement with the streaks observed by the SAR images. During evening when the convective conditions over land diminish, the streaky structures over the sea are still seen in the horizontal wind field; however, the vertical component is close to zero. Thus advected feature from a land surface can affect the wind field considerably for long times and over large areas in coastal regions. Although boundary layer rolls are a well-studied feature, no previous study has presented results concerning their persistence during situations with advection to a strongly stratified boundary layer. Such conditions are commonly encountered during spring in coastal regions at high latitudes.

Comparative studies on traffic-derived particulate matter (PM) from fuel combustion and non-exhaust sources are scarce. This study compares cytokine release (CXCL8, IL-1α, IL-1β, TNFα) and expression of genes linked to inflammation (CXCL8, IL1A, IL1B, COX2, IL6), xenobiotic metabolism (CYP1A1) and redox responses (HMOX1) in human bronchial epithelial cells (HBEC3-KT) and THP-1-derived macrophages after exposure to samples of tire and road wear particles (TRWP) and diesel exhaust particles (DEP). CH223191 was used to assess the involvement of the aryl hydrocarbon receptor (AhR) in the cytokine responses. The results show that TRWP and DEP induced pro-inflammatory responses in both cell types. Moreover, exposure to TRWP and DEP in combination enhanced the pro-inflammatory responses in HBEC3-KT. While the relative potency of TRWP differed between the cell types and endpoints, pro-inflammatory responses of similar or greater magnitude than DEP were observed. The AhR inhibitor CH223191 attenuated the particle-induced cytokine release in HBEC3-KT, but not in the THP-1-derived macrophages. In conclusion, TRWP and DEP induced pro-inflammatory responses in human bronchial epithelial cells and macrophage-like cells, acting through different mechanisms. Responses of a similar magnitude as DEP were observed after exposure to TRWP, showing that TRWP constitutes a potential health hazard. Moreover, the enhanced responses following exposure to TRWP and DEP in combination suggest that the interplay between PM components could be a contributing factor in PM-induced health effects.