When people ask me what I do for a living, I usually say I am an atmospheric chemist. Since this term doesn't mean much to most people, I usually go on to say that atmospheric chemists study issues like acid rain, ozone depletion, and smog. Atmospheric chemists don't have to know as much chemistry as real hard core chemists do, but it is very important to know something about the weather, the global circulation, clouds, and radiation, because all of these processes affect the distribution of chemical species in the atmosphere. This is opposite to the situation in physics and chemistry, which tends to search for progressively more detailed explanations at smaller and smaller spatial and temporal scales. For example, the propagation of solar radiation is especially important in atmospheric chemistry because most chemical reactions in the atmosphere are ultimately initiated by sunlight - visible and ultraviolet radiation split molecules into fragments, each of which can go on to react with some other molecule, and so on.
Atmospheric chemists come in three basic flavors.
Some atmospheric chemists spend most of their time in laboratories trying to measure chemical rate constants that are relevant to the atmosphere. Other atmospheric chemists spend a lot of time outdoors, measuring the concentrations of chemical species, often in exotic far away places. I am mostly a modeler, but work very closely with measurements, and have been involved in some field work on the environmental cycling of mercury. Below are some of my recent research areas. The troposphere is the atmospheric layer closest to the earth's surface.