Abstract

The nighttime boundary layer was studied in an urban area surrounded by tropical forest by use of a copter-type unmanned aerial vehicle (UAV) in central Amazonia during the wet season. Fifty-seven vertical profiles of ozone concentration, potential temperature, and specific humidity were collected from surface to 500 m above ground level (a.g.l.) at high vertical and temporal resolutions by use of embedded sensors on the UAV. Abrupt changes in ozone concentration with altitude served as a proxy of nighttime boundary layer (NBL) height for the case of a normal, undisturbed, stratified nighttime atmosphere, corresponding to 40% of the cases. The median height of the boundary layer was 300 m. A turbulent mixing NBL constituted 28% of the profiles, while the median height of the boundary layer was 290 m. The remaining 32% of profiles corresponded to complex atmospheres without clear boundary layer heights. The occurrence of the three different cases correlated well with relative cloud cover. The results show that the standard nighttime model widely implemented in chemical transport models holds just 40% of the time, suggesting new challenges in modeling of regional nighttime chemistry. The boundary layer heights were also somewhat higher than observed previously over forested and pasture areas in Amazonia, indicating the important effect of the urban heat island.

Highlights

  • The nighttime boundary layer (NBL) occurs in response to surface cooling associated with the emission of long-wave radiation into space, causing a temperature inversion in the overlying atmospheric column at a maximum vertical extent of about 500 m [1]

  • An unmanned aerial vehicle equipped with a chemical sensing system was used to investigate the vertical profiles of nighttime ozone concentration during the wet season in an urban region of central Amazonia

  • The ozone concentration was observed to increase from the surface layer to the boundary layer top as a result of reactive dry deposition and chemical losses in the surface layer

Read more

Summary

Introduction

The nighttime boundary layer (NBL) occurs in response to surface cooling associated with the emission of long-wave radiation into space, causing a temperature inversion in the overlying atmospheric column at a maximum vertical extent of about 500 m [1]. For this atmospheric structure in its theoretical state, conditions of atmospheric stability result, and there is little or no vertical mixing between the surface layer and the altitudes above the NBL [1]. In urban regions, the effects of a heat island, meaning an elevated surface temperature relative to adjacent non-urban regions, can further affect the development of the NBL [9]

Methods
Results
Conclusion
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.