Abstract
We use various temperature profilers located in and around New York City to observe the structure and evolution of the thermal boundary layer. The primary focus is to highlight the spatial variability of potential-temperature profiles due to heterogeneous surface forcing in an urban environment during different flow conditions. Overall, the observations during the summer period reveal the presence of thermal internal boundary layers due to the interaction between the marine atmospheric boundary layer and the convective urban environment. The summer daytime potential-temperature profiles within the city indicate a superadiabatic layer is present near the surface beneath a mildly stable layer. Large spatial variability in the near-surface (0–300 m) potential temperature is detected, with the thermal profile in the lower atmosphere uniquely determined by the underlying surface forcing and the distance from the coast. The summer and winter average night-time potential-temperature profiles show that the atmosphere is still convective near the surface. The seasonal averages of mixing ratio show large variability in the vertical direction.
Highlights
The primary focus is to highlight the spatial variability of potential-temperature profiles due to heterogeneous surface forcing in an urban environment during different flow conditions
We do not refer to these experiments to provide an exhaustive list of urban boundary-layer studies, but to emphasize the fact that very few observations exist on the thermal characteristics of the urban boundary layer (Barlow 2014)
Downstream, less stable layers can be seen at the City College of New York (CCNY) and John F. Kennedy International Airport (JFK) locations, with gradients of 6.6 and 3.5 K km−1, respectively, since roughness elements may be generating turbulence, resulting in a near-adiabatic layer extending from the surface up to 200 m at the CCNY site, and up to 375 m at the JFK site
Summary
Key knowledge gaps exist in our understanding of boundary-layer processes over coastal cities where the population is projected to increase in the coming years (United Nations 2015). The climatology of coastal cities is simultaneously influenced by the additional convection resulting from anthropogenic activities and sea-breeze incursion, leading to an uncertain
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