The field of atmospheric sciences, which includes chemistry, physics, and meteorology, is dependent on observations. It is not possible to reproduce in a laboratory all the chemical reactions and motions of air that occur in the real atmosphere. This means that numerous observations must be made on many different time and size scales. The time or temporal scales can range from a few minutes to many decades. The size or spatial scales can range from under one kilometer to thousands of kilometers, indeed, to the entire world (e.g., satellite measurements). Therefore, observing the atmosphere requires a diverse set of measurement tools. These tools take the form of different sorts of instrumentation. We must be able to operate a diverse set of instruments from different locations. Where we operate the instrument depends on what component of the atmosphere we are observing. Measurements can be made from: (1) space; (2) balloons; (3) aircraft; and (4) the ground. The set of instruments used in any of these four locations is referred to a platform. Thus, we speak of space-based or satellite platforms, balloon platforms, aircraft platforms, and ground based platforms. Each platform makes a unique set of measurements, and each has its advantages and disadvantages, but all contribute to a better understanding of Earth's atmosphere.

1.1 Lecture Objectives

When you complete the reading of this discussion you should be able to