Weather Instruments WHAT IS WEATHER

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1 TOPIC TWO 1

2 WHAT IS WEATHER Weather is the combined short-term conditions found in the lower atmosphere. These conditions include precipitation, or rain and snow, as well as wind, pressure, storminess, cloudiness, and various other atmospheric conditions. What will the weather be like in exactly 37 days? Will it be erratic and very difficult to project. Weather is an ever changing short-term, localized phenomena. Weather Instruments A THERMOMETER measures the air temperature. Most thermometers are closed glass tubes containing liquids such as alcohol or mercury. When air around the tube heats the liquid, the liquid expands and moves up the tube. A scale then shows what the actual temperature is. A BAROMETER measures air pressure. It tells you whether or not the pressure is rising or falling. A rising barometer means sunny and dry conditions, while a falling barometer means stormy and wet conditions. An Italian scientist named Torricelli built the first barometer in

3 Rain gauges usually measure rain in millimeters or inches. By looking at the level of water in the graduated cylinder and the measurement lines, you can determine the total rainfall. For example, if it rained hard all day and you looked at your rain gauge, the level of water might rise to the 1/2 inch mark. This means that 1/2 inch of rain fell on the ground in that spot Meteorologists use an anemometer to measure the speed of wind. An anemometer looks like a bar with small measuring cups attached at the top like the spokes of a bicycle. As the wind blows, it pushes the cups so they spin around the bar like a pinwheel. If the wind is blowing slowly, then the cups will spin around slowly. If the wind is blowing hard, then the cups will spin around fast, and you will probably want to hold on to your hat! 3

4 A WIND VANE is an instrument that determines the direction from which the wind is blowing. Another type of wind vane is the WIND SOCK, usually found in airports and airfields. WEATHER SATELLITES are used to photograph and track large-scale air movements. Then meteorologists compile and analyse the data with the help of computers. 4

5 The Stevenson Screen or thermometer screen is a standard shelter (from rain, snow and high winds, but also leaves and animals) for meteorological instruments, particularly wet and dry bulb thermometers used to record humidity and air temperature. It is kept 1.25m/4.1ft (UK standard) above the ground by legs to avoid strong temperature gradients at ground level, has louvred sides to encourage the free passage of air, and is painted white to reflect heat radiation, since what is measured is the temperature of the air in the shade, not of the sunshine. YOUR EYES are one of the best ways to help detect the weather. Always keep an eye at the sky and you'll usually be on top of weather conditions. 5

6 RAIN How does rain form? Water droplets form from warm air. As the warm air rises in the sky it cools. Water vapor (invisible water in the air) always exists in our air. Warm air holds quite a bit of water. For example, in the summer it is usually very humid. When enough of these droplets collect together, we see them as clouds. If the clouds are big enough and have enough water droplets, the droplets bang together and form even bigger drops. When the drops get heavy, they fall because of gravity, and you see and feel rain. What causes rain? When clouds develop or rain occurs, something is making the air rise. Several things can make this happen. Mountains, low-pressure areas, cold fronts, and even the jet stream. How big are raindrops? Raindrops are much smaller than we think! They are actually smaller than a centimetre Raindrops range from 1/100 inch (.0254 centimetre) to 1/4 inch (.635 centimetres) in diameter. 6

7 TEMPERATURE What is temperature? Temperature is a degree of hotness or coldness the can be measured using a thermometer. It's also a measure of how fast the atoms and Temperature is measured in degrees on the Fahrenheit, and Celsius scales What is the Wind Chill Index? The wind chill index is the temperature your body feels when the air temperature is combined with the wind speed. The higher the wind speed the faster exposed areas of your body lose heat and the cooler you feel. What is the Heat Index? The Heat Index is a combination of air temperature and humidity that gives a description of how the temperature feels. This is not the actual air temperature. Heat Stroke is the most severe form of heat injury and is a life-threatening emergency. It is the result of long, extreme exposure to the sun, in which a person does not sweat enough to lower body temperature. Take a look at the chart below to see what the Heat Index needs to be for you to get heat stroke. 7

8 WIND What is wind? Wind is air in motion. It is produced by the uneven heating of the earth s surface by the sun. Since the earth s surface is made of various land and water formations, it absorbs the sun s radiation unevenly. Two factors are necessary to specify wind: speed and direction. What causes the wind to blow? As the sun warms the Earth's surface, the atmosphere warms too. Some parts of the Earth receive direct rays from the sun all year and are always warm. Other places receive indirect rays, so the climate is colder. Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow. What is a windstorm? A windstorm is just a storm with high winds or violent gusts but little or no rain. 8

9 Climate graphs are used to illustrate the average temperature and rainfall experienced at a particular place over the course of a year. Climate graphs are a combination of a bar graph and a line graph. Temperature is shown on a line graph, with the figures being shown on the right side of the graph. Rainfall is shown by a bar graph, with the figures being shown down the left side of the graph. 9

10 Interpreting climate graphs In the exam you may be asked to look at the information in a graph and describe the area's climate. 1. Look for patterns in the temperature data Is the temperature the same all year round? If it is different, how many seasons does the location experience? Which season is the warmest? Is it warm (10 to 20 C), hot (20 to 30 C) or very hot (above 30 C)? Which season is the coolest? Is it mild (0 to 10 C), cold (-10 to 0 C) or very cold (below -10 C)? What is the range of temperature? (Subtract the minimum temperature from the maximum temperature). 2. Look for patterns in the rainfall data Does the rainfall occur all year round? What is the pattern of the rainfall? Check which season is drier or wetter than others. What is the total annual rainfall? Add each month's total together to get the annual total. Then put the rainfall and temperature information together - what does it tell you about this area? 3. Describe the patterns in temperature and rainfall, including how they relate to each other. You now have a description of the climate. Now look again at the climate graph above. What can you deduce about the climate? 10

11 Climate What is climate? Climate is the average weather usually taken over a 30-year time period for a particular region and time period. Climate is not the same as weather, but rather, it is the average pattern of weather for a particular region. Weather describes the short-term state of the atmosphere. What is our climate system? Atmosphere The atmosphere covers the Earth. It is a thin layer of mixed gases which make up the air we breathe. This thin layer also helps the Earth from becoming too hot or too cold Oceans Oceans cover about 70 percent of Earth's surface. Their large size and thermal properties allow them to store a lot of heat Land Land covers 27 percent of Earth's surface and land topography influences weather patterns. Ice Ice is the world's largest supply of freshwater. It covers the remaining 3 percent of Earth's surface including most of Antarctica and Greenland. Ice plays an important role in regulating climate, because it is highly reflective. Biosphere The biosphere is the part of Earth's atmosphere, land, and oceans that supports any living plant, animal, or organism. It is the place 11

12 CLIMATIC ZONES OF THE WORLD Polar - very cold and dry all year Temperate - cold winters and mild summers Arid - dry, hot all year Tropical - hot and wet all year Mediterranean - mild winters, dry hot summers Mountains (tundra) very cold all year 12

13 MAKE A THERMOMETER MATERIALS: clear, plastic bottle (11oz. water bottle works) water rubbing alcohol clear plastic drinking straw modelling clay food colouring PROCESS: Fill about 1/4 of the bottle full with equal parts of water and rubbing alcohol. Add a few drops of food colouring. Put the straw in the bottle, but don't let it touch the bottom. Use the modelling clay to seal the neck of the bottle, so the straw stays in place. (Make sure the straw does not touch the bottom of the bottle.) Hold your hands on the bottom of the bottle and watch the mixture move up through the straw. EXPLANATION : Why does this happen? Just like any thermometer, the mixture expanded when it was warmed. This made the mixture no longer fit in the bottom of the bottle. As the alcohol expanded the coloured mixture moved up through the straw. If the bottle were to get extremely hot, the mixture would have come up the top of the straw. 13

14 MAKE A RAIN GAUGE MATERIALS: clear jar Ruler PROCESS: Put a jar outside in an open area before it starts raining. After it stops raining, measure how many inches of rain are in the jar with your ruler. *You can also use a jar to see how much water is in snow. Put an inch of snow in a jar, then bring it inside and let it melt. Heavy wet snow will have a lot more water in it than dry fluffy snow. EXPLANATION: You ve just created your own rain gauge and can measure how much you received from the storm. 14

15 MAKE AN ANEMOMETER MATERIALS: 5 three ounce paper Dixie Cups 2 soda straws pin paper punch scissors stapler sharp pencil with an eraser PROCESS: Take four of the Dixie Cups and use the paper punch to punch one hole in each, about a half inch below the rim. Take the fifth cup and punch four equally spaced holes about quarter inch below the rim. Then punch a hole in the centre of the bottom of the cup. Take one of the four cups and push a soda straw through the hole. Fold the end of the straw and staple it to the side of the cup across from the hole. Repeat this procedure for another one-hole cup and the second straw. Slide one cup and straw assembly through two opposite holes in the cup with four holes. Push another one-hole cup onto the end of the straw just pushed through the four-hole cup. Bend the straw and staple it to the one-hole cup, making certain that the cup faces the opposite direction from the first cup. Repeat this procedure using the other cup and straw assembly and the remaining one-hole cup. Align the four cups so that their open ends face in the same direction either clockwise or counter-clockwise around the centre cup. Push the straight pin through the two straws where they intersect. Push the eraser end of the pencil through the bottom hole in centre cup. Push the pin into the end of the pencil eraser as far as it will go. Now your anemometer is ready for use! 15

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