On slightly larger scales, urbanization can also lead to changes in precipitation above and downwind of urban areas. In fact, urbanization alters just about every element of climate and weather in the atmosphere above the city, and sometimes downwind of the city. Although cities themselves form a very small fraction of the Earth's surface area, the world's population has become increasingly urbanized and is now affected by urban climates. Cities too, are important sites for greenhouse gas emissions because of the high energy demands by urban residents and activities. Locally altered urban climates that have existed for many years may provide us with some insight into how to respond to large scale climate change and this makes the study of urban climates increasingly important.
Urban climatologists study a range of problems.
Some urban climatologists specialize in understanding atmospheric processes, and therefore use knowledge and techniques from the fields of geography, meteorology, chemistry, physics and biology to study problems such as air pollution, turbulence, precipitation effects, urban heat islands, and representing urban areas in numerical models. The right-hand photograph shows the extended tower with the skyline of the Shinjuku area of Tokyo in the background. My own research focuses on urban surface temperatures. The surface temperature is an important quantity that plays a role in many environmental processes. The surface temperature is a measure of the state of energy exchange at the surface and therefore combines the influences of a number of processes that occur at the surface such as radiative exchange, subsurface heat storage, evaporation and turbulent heat fluxes.