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Course: Middle school Earth and space science - NGSS > Unit 3
Lesson 2: WeatherWeather
Weather is the state of the atmosphere at a given place or time. Changes in weather are causes by air masses interacting to form weather fronts, such as cold or warm fronts. Because weather is so complex, weather predictions are only probabilities and not definite outcomes. Created by Khan Academy.
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- what is the most powerful/destructive form of weather(7 votes)
- how deep can the global winds reach into the oceans.(6 votes)
- jet streams push the weather system. Global winds or jet streams are always(or most of the time i could be wrong) in the atmosphere.(1 vote)
- can hale come in different sizes?(4 votes)
- Hail can come in many different sizes, from as small as a pebble, to as large as a base ball, and sometimes larger. Hail can also start small and melt before it hits the earth.(4 votes)
- Why does she say National Aeronautics and Space Administration, instead of just NASA?(3 votes)
- Some people might not know what NASA is.(5 votes)
- what does preciption mean(4 votes)
- Precipitation is rain, snow, hale and sleet.(4 votes)
- how deep can the global winds reach into the oceans(3 votes)
- queva apasar si el sol no ay(3 votes)
- Todos moriríamos de frío por la falta de calor. Primero moriríamos de hipotermia. Entonces, si algo todavía estuviera vivo, moriría por falta de oxígeno, porque las plantas necesitan luz solar para realizar la fotosíntesis y producir oxígeno. Pero, de nuevo, si algo lograra eliminar el sol, sería probable que también eliminara la tierra.
Also can you please speak english.(2 votes)
- wet is hepling hi(3 votes)
- why do seasons matter to us(2 votes)
- They can affect temperatures and crops.(3 votes)
- does water fall from above the atmosphere(2 votes)
- Yes, in the form of rain and snow, and other forms. The word is precipitaion.(2 votes)
Video transcript
- [Narrator] Have you ever
gotten up in a good mood, put on your absolute favorite outfit, went outside to have a fun day in the sun, and then ended up soaking wet, caught in a sudden rainstorm? Yeah, same. Unfortunately, we can't
control the weather. Weather changes from day to day and from place to place, so scientists have to consider
a lot of different factors to understand it. Weather can refer to humidity, or amount of water vapor in the air, temperature, air pressure, wind, and, of course, precipitation
like rain or snow. When heat from the sun enters
Earth's lower atmosphere, it affects the temperature
and humidity of the air. As this National Aeronautics and Space Administration map shows, air masses with certain characteristics tend to form in similar places. There's many ways to
classify these air masses, but to keep it simple, these blue blobs represent
colder air masses, which tend to be closer to the poles, and the red blobs
represent warm air masses, which are often found near the equator, where the sun's energy is strongest. The qualities of an air mass may also depend on where it forms. Air masses that form over land
tend to have less humidity than those that form over an ocean. Air masses can even change
characteristics as they move. For example, when a very
cold and dry air mass moves over the ocean, it will likely pick up
warmth and moisture, transforming it into a slightly warmer and more humid air mass. Weather results from these air masses moving from areas with high air pressure to areas with low air pressure. When this happens, a high- or low-pressure system can form. A high-pressure system has
higher pressure at its center than the areas around it, so air moves out from the center. High-pressure systems
typically bring clear skies. A low-pressure system has
lower pressure at its center than the areas around it, so air is sucked into
the center of the system. Low-pressure systems typically
bring more intense weather. Why is this? Well, low-pressure systems are often associated
with what we call fronts. A front is a boundary that forms when air masses of different
temperatures collide near Earth's surface. Different types of fronts can then form depending on how those air masses meet. A warm front occurs when a warm air mass moves in
to a replace a cold air mass. Since warm air is less
dense than cold air, it rises above the colder air, causing a lot of overcast
skies, moderate rain or snow, and warm temperatures. A cold front occurs when
a cold air mass moves in to replace a warm air mass. The dense cold air pushes
the warmer air mass upward, causing larger clouds to build overhead and bringing heavy rain or thunderstorms, strong winds, and cool
temperatures with them. Weather is so complex that it can be difficult to
predict what will happen next. Luckily, scientists have
developed technologies that help model weather patterns so we can all make more informed choices about what to expect when we go outside. To do that, they set up tools like satellites and Doppler radar to observe atmospheric conditions such as wind speed,
temperature, air pressure, and nearby geographic features. They can input the data they
record into computer models, which can use that information
to predict future weather. Have you ever seen a map like this used in a weather forecast? This National Oceanic and
Atmospheric Administration map uses data from a Doppler radar station that measured the
progression of a severe storm over the Northeastern United States. The most intense central
parts of the storm are shown in red, with colors down the rainbow representing progressively less
intense parts of the storm. As technology has advanced, these weather reports
have gotten more accurate, but with so many factors to consider weather is still only
somewhat predictable. That's why you'll always hear probabilistic weather predictions, providing a percentage that refers to how confident the model is that the prediction will happen. If your local weather forecast says there's a 30% chance of rain, it's less likely, but still possible that you're going to get rain. If it says there's a 90%
chance of snow on another day, you're most likely going to get snow. Even if weather
predictions aren't perfect, it's amazing that scientists
figured out how to understand such a complicated phenomenon. Without modern tools and models, it would be much more
difficult for us to plan ahead and be prepared for
possible weather hazards. Next time you have a
fancy day out planned, be sure to check the weather
forecast before you go. If it says there's a
decent chance of rain, don't forget your umbrella.