Weather and Climate Notes

What is Weather vs. Climate Weather is: the current atmospheric conditions, which includes , , , etc.

• The average weather in a given area is the climate for that area. • Example: The weather in Lake Dallas, TX on June 5th is 95° F and warm, but the climate for the area during summer is hot and dry.

Latitude and Longitude • What is ? Longitude? • Latitude = lines that measure North to South - go from the poles at 90° to the equator at 0°

• Longitude =is measured from the Prime Meridian with positive values going east and negative values going west.

• You can determine climate based on the latitude and longitude. – For example: at the equator what is the climate like? What about at the north and south poles?

What affects an area’s climate. • Cycling of in and out of the plays an important role in determining weather and climate patterns. • What is the cycling of water in the atmosphere called? The

• Terms to know: , , , Transpiration, Run-off, Groundwater, Surface water

• CONVECTION CURRENTS – Uneven heating of the 's surface that produces weather systems

• Where hot air rises (less dense) and cooler air sinks (more dense)

Draw in picture on slide Shows the convection current cells around the globe

Sun’s role in convection currents

• You know that it is warmer at the equator than at the poles because the earth is tilted.

• Direct rays of the at the equator and indirect rays at the poles.

• The warmer, lighter air at the Equator moves toward the cooler air at the poles. The cold heavy air at the poles moves toward the Equator. • This causes a constant movement of air called convection currents.

Convection Currents

• Convection currents- drive wind patterns that affect climate.

Air Masses

• Air masses are moved by convection currents. • There are two types of air masses; cold and warm. – Cold = dry and dense

– Warm = moist and less dense

• Cold air masses come from higher to lower latitudes. Warm air masses do the opposite.

When they meet in the middle some interesting weather happens!

Cold Meets The Warm

• Why is the warm air rising and going on top of the cold air mass? Because warm air is less dense!

Air Masses • Air masses are classified by two letters. • The first letter shows what the air mass forms over: • Continental (c) - dry air masses that form over land

• Maritime (m) – moist air masses that form over water

Air Masses • Second Letter tells the latitude and the temperature. • Arctic (A) – cold dry air mass

• Polar (P) – cold dry air mass (not as cold as arctic)

• Equatorial (E) – warmest air mass

• Tropical (T) – warm air mass (not as warm as equatorial)

Air • This is how scientists measure air pressure. Air pressure –Air pressure is the amount of pressure exerted on a surface by the atmosphere above it.

– Barometers are used to measure this with units in millibars (mb).

What is this graph telling us? • As the increases what happened to the air pressure? It decreases

High Pressure System • The air molecules packed into the center of a high pressure system doesn’t make the right conditions for and precipitation development

• So weather is generally calm around a high pressure center.

Low Pressure System

• This is an area where air is rising and this fuels weather change. With rising air means rising water vapors which leads to and the rest of the water cycle.

• Hurricanes, and other storms are associated with associated with low pressure.

Fronts • Fronts- boundaries between two air masses

• They are created when a high pressure systems moves in around a low pressure system.

• They bring WEATHER CHANGES

What Are Main Types of Fronts? • A cold front forms when a fast cold air mass runs into a slow warm air mass. • A cold front brings heavy or .

• After the front passes- cold dry air moves in, skies clear, shift, and drop

. What Are Main Types of Fronts? • A warm front forms when a fast-moving warm air mass overtakes a slower-moving cold air mass. • After the front passes, weather tends to be warm and more humid.

What Are Main Types of Fronts? • An occluded front forms when a warm air mass is caught between two cooler air masses. • Occluded fronts cause weather to turn cloudy and rain or snow may fall. What Are Main Types of Fronts? • A Stationary Front forms when air masses meet, but neither can move the other. • Stationary fronts often bring many days of clouds and precipitation.

Isobars and Symbols • Isobars are lines that show areas with equal air pressure.

• Cold front –

• Warm front –

• Stationary Front –

• Occluded Front –

Weather Maps A weather map can be used to predict temperature and precipitation for several days in a given area

Station Symbols • You will see symbols from weather stations.

• They tell information about cloud cover, barometric pressure, dew point, temperature, current precipitation, etc.

Winds • Winds move excess around the Earth.

• They are caused by air flowing from high to low pressures!

• When air moves downward you have high pressure develop. • When air rises you have low pressure develop.

• Winds do not all blow the same direction though they are affected by two main things:

• Coriolis Effect – Winds are forced to the right in the and to the left in the

• Convection cells – Heat from the sun powers these.

Draw the picture of wind directions and names

Ocean Currents currents affect local and global weather conditions. • They have a much slower, long lasting effect on climate than winds. • They move slowly and retain more heat than the atmosphere. • They are driven by the Sun and the rotation of the Earth (Coriolis Effect).

Types of Ocean Currents Surface Currents – driven by winds. Only 10% of water in the ocean - only the top layer. – a surface current that travels along eastern part of the US – causes warmer climates in Europe.

Deep Water Currents – these are colder (denser) layers that make up 90% of the ocean currents. They are caused by the change in causes these currents

El Niño • El Niño is a mass of warm water that moves eastward as relax. • Originates in the PACIFIC OCEAN. • The warm water brings torrential to parts of the world that are not prepared for such weather. • For reasons that scientists still do not completely comprehend, every few years the trade winds blow less or stop blowing at all. They can also change direction. • It causes a build-up of warm water off the coast of South America and Africa and causes weather changes all over the globe.

Hurricanes and Cyclones • A - is a huge revolving storm that is caused by winds blowing around a low pressure area. • Tornados are also a type of cyclone with a tighter, faster spinning vortex of wind. • Cyclones develop over the over the near the equator • . A cyclone will not develop unless the surface water temperature is at least 26° C (80° F). Warm air rises and creates area of low pressure.

Hurricanes and Cyclones • A hurricane - is a huge storm that forms over warm ocean water • The main purpose of a hurricane is to move heat away from the tropics. So the sun is the main energy source for hurricanes. • Types of damage caused by hurricanes reaching land are strong winds, flooding, storm surge, and tornadoes