The Relationship Between Air Pressure and Weather By: Laura Capps, Kylie Rife, Shannon Collyer and Lindsay Freebourn

Relationship to Elementary Classroom Standards – 4th grade Nature of Science (2010) Make predictions and formulate testable questions.  Design a fair test. Plan and carry out investigations—often over a period of several lessons—as a class, in small groups or independently. Perform investigations using appropriate tools and technologies that will extend the senses. Use measurement skills and apply appropriate units when collecting data. Test predictions with multiple trials. Laura

Relationship to Elementary Classroom Standards (cont.) – 4th grade Nature of Science Keep accurate records in a notebook during investigations and communicate findings to others using graphs, charts, maps and models through oral and written reports. Identify simple patterns in data and propose explanations to account for the patterns. Compare the results of an investigation with the prediction. Laura

What is Air Pressure? Force applied on a given object by the weight of tiny particles of air also known as air molecules. Kylie

High Air Pressure Vs. Low Air Pressure The amount of “empty” space between air molecules determines whether the air pressure is high or low. If particles are more compressed and there is less empty space, then the air pressure is high. If particles have more “empty” space between them, then particles have more freedom to move, which results in low air pressure. Kylie

Barometers Function = measure changes in air pressure Types Aneroid barometers Fluid barometers Mercury Homemade Balloon Water bottle Laura

Consultant: Steve Smith K-12 Outreach Coordinator for Purdue Department of Earth, Atmospheric, and Planetary Sciences Provides materials and activities to teachers in surrounding schools Provided us with our materials and suggestions for barometers Laura

Balloon Barometer Change in pressure measured by movement of toothpick Toothpick above zero line = increased pressure Toothpick below zero line = decreased pressure Limits Qualitative data Relative to air pressure at which barometer was 1st zeroed Affected by temperature changes Laura

Water Bottle Barometer Changes in pressure measured by change in level of water in bottle Water level in bottle above zero line = increased pressure Water level in bottle below zero line = decreased pressure Limits Very dependent on proper water levels and materials Qualitative data Relative to air pressure at which barometer was 1st zeroed Laura

Consultant: Nick Barber He is a graduate from Purdue with a Bachelor’s in Meteorology. Started the Purdue Weather Facebook page and passed on the responsibility when he graduated. Now holds an administrative position at the CoRec Shannon

How does air pressure affect weather? Weather affects air pressure by increasing or decreasing it depending on what sort of weather is occurring at the time You can have pressure drops in association with a cold front (which is usually accompanied by rain and thunderstorms, possibly severe if all the ingredients are sufficiently present). After the passage of weather systems, pressure tends to increase, which brings about clearing. This happens at the surface and with altitude. Shannon

Air Pressure and Weather cont. When air at the surface is heated by the sun, it begins to rise via convection This causes surface pressure to decrease and pressure above to increase, which, if the air is moist, will produce clouds, and potentially rain and thunderstorms. Shannon

Air Pressure Around the World Air pressure is dependent upon altitude through a pretty simple equation that relates the two indirectly (i.e. as altitude increases, air pressure decreases exponentially) Pressure is also dependent upon temperature and air density, which is usually averaged to one value, but different regions can have different air densities, thus providing you with differing pressures. Shannon

Around the World Cont. One particular region of interest is central band aka the Equatorial Low Pressure Zone, which is more commonly referred to as the Inter-tropical Convergence Zone (ITCZ). Shannon

Shannon

Cont. This is also seen on a smaller time scale with any coast line where this differential heating zone sets up, which causes what are called 'sea or lake breezes', depending upon the body of water. Shannon

Shannon

Things to Keep in Mind Air is warmed near a warm surface. So, the air closest to the earth will be warmed the most. As air rises, temps begin to drop The number of air particles decrease as the altitude increases As air rises the pressure from the air above decreases.

How Air Pressure Relates to Weather Weather is based on high air pressure and low air pressure. Low air pressure = cloudy and rainy weather This happens because the air is rising and condenses into clouds and rain. High air pressure = sunny and dry weather This happens because the air stays low and it tends to stay dry as the air sinks.