Analytical Description and Vertical Structure of the Atmospheric Boundary Layer - Surface Based Remote Sensing of the Atmospheric Boundary Layer - page 22

Fig. 2.5 Urban plume downwind of a larger city. This is a special case of an internal boundary
layer (cf. Fig. 2.3 )

In a horizontal flow, the presence of the city is a change in surface properties.
Following Section 2.2.1.4 , this leads to the formation of internal boundary layers
(Fig. 2.5 ). The internal layer formed by the properties of the urban surface is often
called urban plume.
Following Plate ( 1995 ), Roth ( 2000 ), and Piringer et al. ( 2007 ), the urban
boundary layer (UBL) is usually divided into four layers (Fig. 2.6 ). The lowest one

Fig. 2.6 Vertical layering in an urban boundary layer. H gives the average building height, p+ and
p − designate atmospheric pressure disturbances upstream and downstream of single buildings