Build and calibrate a hair hygrometer.

This image shows ER-2 Doppler radar data from Hurricane Emily on July 17, 2005. You are looking at a vertical cross-section of the rain bands in the eyewall. Red colors indicate the most intense rain within the hurricane. Dr. Gerald Heymsfield, another NASA hurricane researcher, collected and compiled these data for the hurricane science team.

1. Design an investigation using your hair hygrometer to examine humidity levels around your home or school. Plan to collect data for at least two weeks. Write out the steps of the procedure that you would follow in your investigation and the purpose of each step.
   
   
2. Conduct your investigation and record your data.
   
   
3. Examine your measurements of the amount of humidity around your home or school. What does your hygrometer tell you about the amount of water in the air in your test location?
   
   
4. Do your results match your expectations? Why or why not?
   
   
5. Do you think this tool is accurate for measuring water in the air? Why or why not?
   
   
6. Did you encounter limitations when using this instrument to measure humidity? Explain.
   
   
7. Research other designs for a hair hygrometer, and compare and contrast your tool to the others you find. If time permits, build one of the other designs you find and compare the accuracy and precision of your two instruments. Recall that accuracy refers to the correctness of a tool’s measurement and precision refers to the tool’s ability to consistently repeat the measurement. 

According to Robbie’s studies, the stronger the signal she gets back from the storm, the more water vapor (and therefore energy) is in the air. The more energy there is, the stronger the storm is likely to be. In her studies, Robbie uses microwaves, which are part of the electromagnetic spectrum. Visible light is also part of that spectrum, and because it is easier to measure, we will use visible light to build our model. In this challenge, you will develop your own model sensor to help you determine the amount of “water” in the air and the strength and behavior of your “monster storms.”

To set up your model sensor, position the flashlight on a flat surface as shown in the diagram and secure it with tape. Use clay to anchor a 4 × 6 white index card in an upright position on the table, 30 cm (12 in.) away from the front of the flashlight. You will use blue plastic light filters to create your storm “signatures.” Before you can read your sensor instrument, however, you will need to calibrate it.

1. To calibrate your instrument, turn on the flashlight and make sure that it is pointing directly at the index card. Cover the light source with one square of the blue plastic filter. What color do you see on the white index card now? Use your colored pencils to illustrate the observed color on your calibration sheet.
   
   
2. Add filters to the light source one at a time. Use your colored pencils to record the observed color each time you add a filter, until the observed color is black. Robbie Hood must calibrate her microwave sensor each time she uses it. Would you need to calibrate your instrument each time you use it? Why or why not?
   
   Using your calibration sheet, divide your observed results into 5 sets, numbering them from 1 to 5, with 5 being the darkest set. This will be your intensity scale. Robbie also produces an intensity scale from her calibrations. The scale helps her determine the amount of water in a storm, when she takes her instrument into the field. In your model, the blue filters represent a storm’s water content.
   
   
3. Your teacher will give you several blue filters taped together in a bundle. You will not know how many layers are in each bundle. Use your calibration sheet to determine the number of filters in each bundle. Assign each bundle an intensity rating from your scale.
   
   
4. Now your teacher will give you a series of bundled filters. The series represents the progression of a storm in 24-hour intervals. Use your sensor instrument to assign an intensity rating to each filter bundle. These ratings will represent the storm’s water content for each 24-hour period. After you assign an intensity rating to each filter bundle, make a prediction for the intensity rating of the next filter bundle your teacher will give you.
   
   
5. Record both your predicted and observed intensity rating data in a table and make a chart of time and intensity to tell the story of your storm.

1. You were asked to predict the strength of a storm based only on the signatures you saw from the previous days. How accurate were you? What other information would have helped you make those predictions?
   
   
2. How does this represent what Robbie Hood sees when she gathers data using microwave radiation?
   
   
3. When you looked at the light source on the paper without any filters, what type of day did that represent (cloudy, clear, rainy, stormy, etc.)? Explain your answer.
   
   
4. How much energy do you think is in the atmosphere on a clear day? Explain your answer.
   
   
5. If water vapor releases heat energy as it rises and condenses, where does that energy go?
   
   
6. What do the blue filters represent from Robbie Hood’s research? The white paper? Explain your answer.
   
   
7. What do the darker blue colors represent in terms of water vapor in the atmosphere? Explain your answer using Robbie’s research methods.

Journal Question   Why is Robbie Hood’s research important for other scientists who study hurricanes?