Downdrafts are one type of the atmospheric condition known as vertical drafts. The primary cause of downdrafts is the movement of air hotter or colder than the air around it. Since hotter air is less dense it will rise until it finds air of a similar density. Colder air is denser and will sink through a process known as subsidence. Downdrafts are also be caused by high pressure regions which attract surrounding air, which sinks as it reaches the center of the region.
Understanding vertical drafts may be done with projects exploring their causes. Have students draw diagrams and posters of high pressure regions and how the movement of air is affected by air density. Have students research the relationship between air density and temperature. Working in two groups -- one for cold air and one for hot air -- have students perform the process of downdrafts. Since cold air denser, the students in this group stand closer together, while the hot air students stand farther apart. As the two pass through each other, the cold air goes below and the hot air goes above, creating a downdraft.
Have students create a tornado, one weather condition caused by downdrafts, by filling a soda bottle to the brim with water. Have the students swirl the bottle to create a vortex in the water. Turn it upside down over the mouth of another bottle to observe the tornado. Simulate thunderstorms by placing a small jar filled with cold, colored water into a larger beaker filled with hot water. Seal the beaker with plastic wrap and a rubber band. When a slit in made in the plastic wrap, the cold water in the jar disperses, simulating a thunderstorm.
In 1985, during a routine landing at Dallas-Fort Worth Airport, Delta Air Lines Flight 191 crashed, killing eight crew members, 126 passengers and one person on the ground. The crash was attributed to a microburst -- a sudden, intense downdraft -- and spurred reform and safety measures in the aviation industry. Have students research how the microburst caused the crash, while studying the physics necessary for planes to take off and land. Have them study the on-board wind shear detection system that became required of commercial airlines after the crash, and how these systems work to detect wind shears, microbursts and downdrafts.