Observational Techniques: Sampling the Mountain Atmosphere

In this chapter several types of instruments are surveyed that have contributed to increased understanding of the structure of atmospheric flows and processes that drive these flows in complex terrain. After a brief example of the use of in-situ measurements, those that are in contact with the air they are measuring, a review of basic remote sensing principles serves as a background for a discussion of several types of remote sensors. The review focuses on active remote sensing systems, those that transmit and receive their own signal, including sodar, radar, radar wind profilers, and lidar. Examples of the kind of data available from each type of system allow an appreciation for how these systems contribute to advanced understanding of atmospheric processes by providing data above the surface and revealing the evolving vertical and horizontal structure of complex terrain flows. Advantages of deploying combinations of complementary instruments are described. The roles of measurements and mesoscale numerical models are discussed in a section where modeling studies have used high-resolution remote sensing and other advanced measurement systems to verify the models. Finally a brief section describes turbulence measurement techniques by remote sensing that may be able to provide profiles of turbulence quantities in mountain studies.