TABLE OF CONTENTS The role of turbulence as a frequent and serious atmospheric hazard to aviation was addressed in Section 3.3. It was pointed out in Chapter 4 that thunderstorms generate some of the strongest turbulence found naturally in the atmosphere. However, atmospheric turbulence is of widespread occurrence, and clear air turbulence is a commonly experienced source of aviation hazard and discomfort. The basic capability of coherent weather radars to sense and measure turbulence through an estimate of the Doppler spectral width was discussed in Chapter 6. In view of the paramount importance of turbulence in the aviation context, this chapter is devoted to a closer and deeper study of some of the fundamental aspects of atmospheric turbulence, and its relationship with aviation on the one hand and radar-measured variables on the other.
Doppler radar is the only remote sensing instrument that can detect tracers of wind, both in the clear air outside precipitation zones and in low-visibility conditions such as those occurring inside heavy rainfall regions and cloud masses. Cloud and precipitation droplets hamper the operation of optical sensors such as lidars by almost completely extinguishing the optical radiation within a few metres of propagation distance. This unique all-weather sensing capability makes the Doppler radar an instrument of choice to survey the wind fields traversed by aircraft. Of particular interest are the spatial and temporal variability of the wind. As mentioned before, wind shear and turbulence relate to two different aspects of this variability. After a short discussion on wind...
