Heating the Earth's Atmosphere & Storm Generation

You will note from reading of the NASA EO website (Lindsey 2009), that not all energy that reaches the upper atmosphere actually reaches the Earth's surface. In fact, less than half of the sun's energy actually reaches the surface due to reflection and absorbence of the light energy by gases in the atmosphere. Given the fact that the Earth surface (land and water) absorbs significantly more light energy which results in thermal energy relative to the atmosphere, most solar heating occurs at the surface closer the equator. Likewise much of the cooling happens in the atmosphere. Thus, heat energy produced at the Earth's surface ultimately is redistributed to the upper atmosphere by processes such as evaporation, convection, and simple thermal radiation.

As shown in this YouTube video produced as an animation from repetitive flights of the Global Hawk UAV (unmanned flight) over Hurricane Karl of 2010, some of this water vapor will climb to more than 12,000 meters above the earth's surface. Once in the upper atmosphere, the heat energy can be lost and radiate out into space. When significant volumes of warm water vapor move upwards, low pressure cells are developed at the Earth's surface and large storms are generated. In the process, water vapor evaporated into the atmosphere will cool and condense. This is ultimately how storm clouds are produced. As the water begins to fall back to the surface, large scale convective cells are generated and the air mass is forced to spin in response to the Coriolis Effect. This causes deflection of air masses to the right in the northern hemisphere and deflection to the left in the southern. In order for storms to sustain themselves, the upward movement of warm water vapor needs to be constantly resupplied or the storm will weaken and eventually fall apart.

For a good model that might help you visualize this process, think about a hot air popcorn maker. As the popcorn is heated, it spins inside the popper's reservoir. Once the popcorn pops, it is blown upward and spirals out of the reservoir where it then falls out of the popper. Without the lid to contain it, the popcorn would flow out in a spiraling pattern and then begin to cool and fall back to the ground. As long as there is popcorn in the popper and heat to generate the uplift, the storm will continue. Once the heat or water vapor is removed, the storm subsides. You could probably find a good video of this process on the web if you need help visualizing this phenomenon.