Abstract
Snow-capped mountains make a picturesque scene, especially in summertime when the peaks are in such contrast to the warmth below. This project shows you a way to see how temperature changes with altitude using data collected twice daily from weather balloons.Summary
Sources
This project is based on:- Millersville University LEAD Undergraduates, n.d. Lead-to-Learn: Exploring Temperature and Pressure Changes with Altitude Millersville University. Retrieved March 27, 2007.
Objective
The goal of this project is to use weather balloon sounding data to investigate how air temperature and pressure vary with altitude.Introduction
Twice a day all over the U.S., the National Weather Service launches weather balloons with instrumentation packages called radiosondes to collect data on the current conditions of the upper atmosphere. As they ascend with the weather balloon, the radiosondes measure profiles of pressure, temperature, and relative humidity. The radiosondes contain radio transmitters that send the collected data back to Earth. The data are used for weather forecasting, and are available online.
You can use this data for a science fair project on atmospheric conditions. We will show you how to read temperature and pressure data from a standard upper air sounding plot—the same graphs that are used by meteorologists for weather forecasting. This project shows you how to find out how the temperature changes with altitude in the lowest layer of the Earth's atmosphere, the troposphere.
Figure 1 shows an example of an upper air sounding plot. This is a standard graph used by meteorologists to analyze data from a balloon sounding. There is a lot of additional information in the graph, but basically it is a plot of temperature (x-axis) vs. height (y-axis). The white data line on the left shows the dewpoint vs. pressure, and the white data line on the right shows the temperature vs. pressure. The pressure (in millibars, mb) is shown on the y-axis in blue lettering, and the height (in m) is shown in white lettering. A sounding plot is also called a "Skew T" plot, because the temperature axis is plotted at an angle (i.e., skew) of 45°. The temperature lines of the Skew T are in blue (at 45°).
A screenshot of an upper air sounding plot with data shown from International Falls, Minnesota on March 23, 2007. Dewpoint and temperature of the atmosphere are plotted with elevation on the left axis, temperature along the x-axis, and wind speed on the right.
Figure 1. Example of an upper air sounding plot from the Unisys Weather webpage. Data shown are from International Falls, MN, March 23, 2007. Brrrrr!
Atmospheric pressure decreases with height above the Earth's surface. The higher you go, the less atmosphere remains above you, so the pressure decreases. "Meteorology uses pressure as the vertical coordinate and not height. This works out better for thermodynamic computations that are done on a regular basis. Pressure decreases in the atmosphere exponentially as height increases reaching 0 pressure in space. The standard unit of pressure is millibars (mb or hectopascals-hPa) of which sea level is around 1015 mb. Here is a table of pressure levels and approximate heights (Unisys Corp., 2001):"
| Pressure | Approximate Height | Approximate Temperature | ||
| (mb) | (m) | (ft) | (°C) | (°F) |
| 1015 (sea level) |
0 | 0 | 15 | 59 |
| 1000 | 100 | 300 | 15 | 59 |
| 850 | 1500 | 5000 | 5 | 41 |
| 700 | 3000 | 10000 | −5 | 23 |
| 500 | 5000 | 18000 | −20 | −4 |
| 300 | 9000 | 30000 | −45 | −49 |
| 200 | 12000 | 40000 | −55 | −67 |
| 100 | 16000 | 53000 | −56 | −69 |
Figure 2 shows how to read the temperature at a chosen pressure level (height). On the y-axis, find the pressure level (in mb) where you want to know the temperature. Follow the horizontal pressure line over until it intersects with the temperature plot (right-hand data plot, in white). Then follow the 45° temperature line down and to the left to the temperature axis. As shown in Figure 2, the temperature at 700 mb was about −11°C.
A screenshot of an upper air sounding plot with data shown from International Falls, Minnesota on March 23, 2007. The plot includes instructions to calculate the temperature at a given altitude and pressure level. To find the temperature at a given pressure level, read straight across the temperature plot, and then follow the blue lines down to the left to find the corresponding temperature.
Figure 2. Reading the temperature of the atmosphere at 700 mb (3022 m) from the sounding plot. Follow the horizontal pressure line to where it intersects with the temperature plot (right hand data line, in white). Then follow the 45° temperature line down and to the left to the temperature axis. In this example, the temperature at 700 mb was about -11°C.
There is a lot more information in the sounding plot, but it isn't important for this project. If you want to learn more about sounding plots, do more research about them online.
In this project you will use balloon sounding data to investigate how atmospheric temperature and pressure change with altitude.
Terms and Concepts
To do this project, you should do research that enables you to understand the following terms and concepts:- Troposphere
- Pressure
- Temperature
Questions
- What is the source of heat for the troposphere?
Bibliography
For more information about the layers of the Earth's atmosphere:
- Sharp, Tim. (2017, October 13). Earth's Atmosphere:Composition, Climate & Weather. Space.com. Retrieved March 3, 2021.
- Cirjak, Antonia. (2020, May 1). What Are The 5 Layers Of The Earth's Atmosphere?. Worldatlas.com. Retrieved March 3, 2021.
For more information on weather balloons:
- UCAR. (n.d.). Exploring the Atmosphere with Weather Balloons. Retrieved March 3, 2021.
For current and archived sounding plots:
- NOAA Storm Prediction Center (n.d.). Observed Sounding Archive. National Oceanic and Atmospheric Administration. Retrieved January 1, 2019.
Materials and Equipment
To do this experiment you will need the following materials and equipment:- Computer with Internet access
- Graph paper or graphing software
Experimental Procedure
- Do your background research so that you are knowledgeable about the terms, concepts, and questions.
- For current weather balloon data from across the U.S., you will need to find sounding plots online, for example from https://www.spc.noaa.gov/exper/soundings/.
- Follow the instructions in the Introduction for reading the sounding plot. Make a table showing pressure (in mb), altitude (in m), and temperature (in °C) for each of the pressure levels shown in the sounding plot.
| pressure (mb) |
altitude (m) |
temperature (°C) |
- Repeat this for at least 5 different sounding stations.
- Make a graph of your results that shows how temperature varies with atmospheric pressure for each station.
- Make a graph of your results that shows how pressure varies with altitude for each station.
Ask an Expert
Variations
- Balloon soundings are taken at 12-hour intervals. (Notice that the time given in the plots is coordinated universal time (UCT), not local time.) Depending on the station location and time of year, you may be able to compare soundings taken during daylight hours to those taken after sundown. Compare several sequential pairs of soundings (daylight/after sundown) for several locations. Do you see any consistent relationships in the two temperature plots? What do they tell you about the sun's contribution to heating different levels of the atmosphere?
- For an experiment that relates atmospheric temperature and characteristics of snow, see the Science Buddies project How Does Atmospheric Temperature Affect the Water Content of Snow?
Careers
If you like this project, you might enjoy exploring these related careers:
