1. Weather
MYP 1

2. What is Weather?
The atmospheric conditions, along with the short-term changes, of a certain place at a certain time.
Can change very rapidly.
Climate is the temperature and weather that are present in an area over a long period of time.

3. Weather Variables
Variables are used by meteorologists to describe a variety of atmospheric conditions:
Air temperature:: measure of the average kinetic energy of molecules in the air
Air pressure: the pressure that a column of air exerts on the air or a surface below it
Decreases as altitude increases
Wind is created when air moves from an area of high pressure to an area of low pressure.
Humidity: amount of water vapor in the air
High humidity = High water vapor= sticky feeling because sweat doesn’t evaporate well
Relative Humidity: The amount of water vapor present in the air compared to the maximum amount of water vapor the air could contain at that temperature.
Dew Point: The temperature at which air is fully saturated because of decreasing temperatures while holding the amount of moisture constant.

5. Pressure Systems Weather is often associated with pressures systems.
Cool air molecules are closer together so they have higher pressure than warm air.
A high-pressure system is a large body of circulating air with high pressure at its center and lower pressure outside the system. They bring sunny skies and fair weather
A low-pressure system is a large body of circulating air with low pressure at its center and higher pressure outside the system. This brings cloudy days with precipitation

8. Air Masses
Large bodies of are that have uniform temperature, humidity, and pressure.
Forms when a large high pressure system lingers over an area for several days.
As a high pressure system comes in contact with earth, the air in the system takes on the temperature and moisture characteristics of the surface below it.

9. Air Masses
Artic Air Masses: Form over Siberia and the artic. Have bitterly cold, dry air. Temperatures can drop to - 40 degrees Fahrenheit
Continental polar air masses: fast moving and bring cold temperatures in winter and cool weather in summer. Located over Canada.
Maritime Polar Air Masses: Forms over the Northern Atlantic and Pacific oceans. They are cold and humid. Often bring Cloudy Rainy Weather.
Continental Tropical Air Masses: Form over the tropics. They are hot and dry. Bring Clear skies and high temperatures. Usually form during the summer.
Maritime tropical Air Masses: Form over Western Atlantic Ocean, Gulf of MEXICO, AND THE Eastern Pacific Ocean. Brings hot humid air to florida and se united states during summer. Winter they bring heavy snowfall.

11. Fronts A weather front is a boundary between two air masses
A cold Front is when a cold air mass meets up with a warm air mass. The warm air rises over and the water vapor cools.
Showers and thunderstorms often form along cold fronts
Often give rise to severe thunderstorms
Warm fronts form when warm air masses meet cold air. Warm air rises as it glides over and creates a wide blanket of clouds
Often bring steady rain or snow for several hours
Causes the wind to shift directions

12. Fronts
Stationary Fronts are when the two different air masses stall. Cloudy skies and light rain are found along stationary fronts.
Cold Fronts move Faster than warm fronts. When a fast-moving cold front catches up to a slow-moving warm front, an occluded front forms. These usually bring precipitation.