Introduction: (Initial Observation)
A weather station is a collection of instruments that can measure and record weather conditions such as wind, air pressure and temperature. Meteorologists use the data from multiple weather stations to forecast weather in a specific region. For example by knowing the speed and the direction of wind, meteorologists can calculate the time that it takes for the clouds to travel from one region to the other. If the path of such clouds is crossing the path of a cold air current, it may result precipitation in the form of rain or snow.
Although I know what weather instruments do, I am wondering how do they do that.
In this project I will study a few weather instruments to determine their work mechanism and try to make at least one weather instrument. I will also put together a weather station with weather instruments that I can gather or build and use them to record the weather data in a period of about seven days. Analyzing the weather data that I collect may help me to find a clear pattern between changes in weather and my gathered data.
Visit your local library and find books about weather and meteorology instruments. Keep track of where you got your information from.
Following are samples of information that you may find:
Meteorologists study the weather by recording and analyzing data. You can become an amateur meteorologist by building your own weather station and keeping a record of your measurements. After a while, you’ll notice the weather patterns that allow meteorologists to forecast the weather.
Following are some weather instruments and what they measure:
Barometer – used to measure the air pressure. In general, rising pressure indicates fair weather while falling pressure indicates foul weather.
Thermometers of various types, including liquid-expansion thermometers, metal-expansion thermometers and digital-electronic thermometers–used to measure temperature.
Weather vanes–used to show the wind direction.
Hygrometers of various sorts–to measure moisture in the air.
When air ascends, eventually it cools so much that water vapor starts condensing out into liquid form. It’s difficult to form a water droplet out of a collection of water molecules in gas form. The water usually needs something to condense onto. The atmosphere has plenty of candidate particles, called condensation nuclei, which allow water to condense onto them in liquid form. As this takes place, you get many, many tiny water droplets, and a cloud is born.
By the way, the visible part of a cloud, and steam or fog for that matter, is all the little liquid water droplets; water vapor (the gas form of water) is transparent.
As the air continues to ascend and cool, and the cloud continues to grow, the existing cloud droplets get bigger and bigger. Well, “bigger” is relative; most cloud droplets are just a few microns in diameter. And such tiny droplets pretty much float in the air without falling.
Raindrops are much bigger than cloud droplets – usually a few millimeters in diameter, hundreds of times the diameter of a cloud droplet. So how do you make big raindrops out of little cloud droplets?
Most precipitation starts out as snow, even though most of what we see at the ground is rain. It is formed several kilometers high in the atmosphere, where the temperature is below freezing, and the snowflakes melt on the way down.
At least, that’s what happens most of the time. Other times, if the air is cold enough, the snowflakes may not melt, and they make it all the way down to the ground as snow. And on rare occasions, other types of precipitation may result.
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to find out what instruments are used in a weather station and learn how they work. Specific questions that we can investigate in this project are:
How does changes in air pressure, temperature and moisture affect the weather condition?
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
The independent variables are changes in temperature, air pressure and moisture.
Dependent variable is weather condition (clear, cloudy, rainy, snowy, windy)
Controlled variables are location, instruments and methods of observation.
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. Following is a sample hypothesis:
High pressure and moisture along with low temperature results rain. Low pressure air results a clear sky.
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
The main experiment in this project involves observation and recording weather data using a weather station . You may use different weather instruments for your weather station. You may choose to purchase them all, or build some of them yourself. The main instruments that you need in a weather station are:
- Hygrometer or Psychrometer
- weather vane (optional)
- rain gauge (optional)
A weather station like the one shown in the right can show temperature, moisture and air pressure. They are normally sold about $29. (I bought one in a garage sale for about $3). Add to that a weather vane (to show the wind direction) and an empty cup (to measure precipitation) and you will be able to observe and record weather conditions.
Although you may gather or purchase all the components that you need for your weather station, I suggest to build some of them yourself.
Some of the instruments that you can make yourself are suggested here in experiments number 2 and 3.
Use your weather station to observe and record weather data.
Every meteorologist needs to keep a good weather journal. Remember, good observations make good forecasts. In this experiment you use your weather station to record weather data.
Place your weather station somewhere outside, away from direct sunlight and excessive moisture. If you live in northern hemisphere, place it in the north part of the house so you will have shade. Also place them on a table to be away from excessive moisture on the ground.
Decide how often you can make observation and recording and make a schedule for yourself. Observations and recording must be done at least once each day. Other options are twice a day (every 12 hours) or four times a day (every 6 hours). During each observation, record the measurements from each of your weather instruments in your weather station. Record your observations in a data table like the one shown below, so that you’ll be able to notice patterns in your weather data. Try to make your observation at the same time every day.
Have you ever seen your breath on a cold day? That’s moisture in your breath, just like the water in clouds, rain, or moisture in the air. How does the amount of moisture in the air change when a storm comes? Can you use moisture to predict a storm? Use the tools below to measure moisture in the air.
Can you measure moisture? Can you use moisture to predict a storm?
Make a Psychrometer (kind of hygrometer)
A psychrometer measures the amount of relative humidity in the air.
- 2 centigrade thermometers
- wet gauze or wet paper towel
- rubber band
- Relative humidity table (shown below)
- Tape the two thermometers on a board about 6 inches apart with the numbers facing up and the liquid filled ends sticking over the edge of the table about 2.5 cm (1 inch).
- Place the wet gauze on the liquid filled end of one thermometer and secure it using the rubber band if needed. If the thermometer that you are using does not have a back plate, wrap the wet gauze around the thermometer bulb and then use the rubber band to hold it in place.
- Blow the fan on the thermometers until the temperature stops falling.
- Write down the temperature on both thermometers.
- Subtract the temperature on the wet thermometer from that of the dry one.
- Look at the table below. Find the dry thermometer temperature on the left and follow it to the right. Find the difference between the two temperatures on the top, and follow it down. The number where the row and column intersect is the relative humidity.
Can you use your psychrometer to predict a storm?
Relative Humidity Table (in percent)
Dry Bulb Minus Wet Bulb (degrees celsius)
How Does it work?
When moisture in the air is low, water evaporates faster. Water evaporation cools of the air and the thermometer shows a drop in the temperature. Using the temperature drop we can determine the moisture in the air.
How can you measure air? Can you see pure air? Can you feel it? Air pressure is the weight of air pressing on every part of your body, and everything around you, right now. Do you think you can use air pressure to predict a storm? Use the tools below to measure air pressure.
In a hurricane, there is very low air pressure. How does pressure change during other storms? Read to see how you can make a barometer. Watch what happens to your barometer during a storm.
Make a Barometer
Do you know what the air pressure is today? You can find out for yourself by measuring the air pressure on a barometer.
- small coffee can
- plastic wrap
- index card
- rubber band
- Cover the top of the can with plastic wrap. Use a rubber band to hold the plastic wrap in place. The cover should be taut making the can airtight.
- PLACE the straw horizontally on the plastic wrap so that two-thirds of the straw is on the can.
- TAPE the straw to the middle of the plastic wrap.
- TAPE the index card to the can behind the straw.
- Carefully record the location of the straw on the index card.
- After 15 minutes, record the new location of the straw on the index card.
- Continue checking and recording the straw location as often as desired.
- Be careful not to place your barometer near a window, as the barometer is sensitive to temperature as well as air pressure.
High pressure will make the plastic wrap cave in, and the straw go up. Low pressure will make the plastic wrap puff up, and the straw go down. Check your measurements with a real barometer.
What happens to your barometer when a big storm comes? Can you use your barometer to predict a storm?
Since barometers are very sensitive to minor changes in weather conditions, you’ll want to keep the barometer indoors to get more accurate readings.
Make a Wind Direction indicator:
A weather vane is also know as a wind direction indicator. The vane points in the direction from which the wind blows.
a long wooden dowel (about the size of a broom stick)
an aluminum pie plate
a 12 inch long piece of wood (A sturdy ruler would work)
a metal washer
small saw (or serrated knife)
wire (for mounting)
scissors (strong enough to cut aluminum)
Begin with the 12 inch piece of wood. Use the small saw (or serrated knife) to cut a vertical slit at each end of the stick. The slit should be about one half inch deep. At the midpoint (exactly halfway) of the top of the stick, hammer one nail all the way through the stick. Then turn the wood around the nail several times until the stick turns easily around the nail.
Refer to the pattern picture and cut the head and tail from the aluminum plate. Glue the head into the slot at one end of the wooden stick. Glue the tail into the other end. Allow time for the glue to dry before you take the vane outside.
Attach the weather vane to the long wooden dowel by placing the metal washer on the end of the dowel and then hammering the nail through the wooden stick and into the wooden dowel. (Refer to the picture.) Make sure that the vane moves freely and easily around the nail.
Now you are ready to mount your weather vane outside. If you mounted your rain gauge on a fence, you may want to mount your weather vane near it. Position the wooden dowel beside the fence and secure it with wire. Try to get the vane as high above the fence as you can while still keeping the dowel steady and secure.
The head of the pointer will always point to the direction from which the wind is blowing. For example, if the head points to the NorthEast, then the wind is blowing from the NorthEast. It’s as simple as that. (A common mistake is to think that the wind is blowing toward the NorthEast.) Record your wind direction readings in your weather journal.
Materials and Equipment:
List of material can be extracted from the experiment section. It depends on the experiments that you choose.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Enter the result of your daily observation in a table like the one provided in the experiment number 1. Also write down any other noticeable observation such as sudden change in weather condition.
No calculation is required for this project.
Summery of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
The same data table can be used as the summery of results.
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
If you noticed any specific pattern that can help you to relate your data to certain weather condition, write the results here. Did your results support your hypothesis? Did your results disprove your hypothesis? Or the results were not conclusive.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested. Following are samples of related questions.
At what temperature range we can expect the precipitation in the form of snow?
At what temperature range we can expect precipitation in the form of rain?
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
Meteorologists have modern instruments that record temperature, pressure and other measurements continuously. Making observations as low as once a day reduces the accuracy of the data and does not allow us to monitor changes that may have happened between two observations. This can potentially cause wrong or inconclusive results.