The paper illustrates how SAR images over the sea may be combined with scatterometer derived wind fields, to study the spatial characteristics of the atmospheric boundary layer (ABL). Both instruments are active microwave radars, relying upon the same physical mechanisms of electromagnetic-sea surface wave interaction. Providing a radar backscatter signature of the sea surface at different spatial resolutions, they make possible to investigate the horizontal (and possibly vertical) structure of the ABL from the mesoscale (< 100 km) down to the intermediate (< 10 km) and small (< 2 km) scales. An example of the multi-scale description of the ABL is provided analysing a SAR image overlapped to a scatterometer wind field. The Ekman vertical velocity has been derived from it, and the bi-dimensional spectrum of the SAR image has been computed. Large scale modulation of the radar backscatter seems related more to the vertical velocity than to the wind speed, while the shorter scale modulations reveal the occurrence of wind rolls. The importance of parameters like the air and the sea surface temperatures in the interpretation of the SAR images is evidenced through the comparison of the spatial structure of the radar backscatter and that of the wind and vertical velocity.