Unit 7 Meteorology 2014… Mrs. Knowlton

Weather describes the conditions in the atmosphere (mostly the troposphere the lowest layer of the atmosphere) at a given place for a short period of time is caused by the uneven heating of the earth by the Sun’s rays

Weather Variables Air Temperature- the amount of heat energy in the atmosphere at a place Air Pressure- is the amount of force exerted by the air hitting a given surface area Humidity- the amount of water vapor in the air Wind Speed- the rate of moving air Wind Direction- the direction that the wind blows FROM Precipitation- failing moisture from clouds (Rain, Snow, Sleet, and Hail)

Weather map symbols

Instruments Sling Psychrometer demo

Convert Air Pressure

Wind Wind- horizontal movement of air which is caused by differences in air pressure. Air moves from HIGH PRESSURE to LOW PRESSURE! The differences in pressure are caused by uneven heating of the earth! HOT AIR RISES=LOW PRESSURE COLD AIR SINKS= HIGH PRESSURE

Wind Direction Wind direction- the direction that the wind is coming from – Example: the wind is coming from the west so the wind direction is WEST – Example 3: the wind is blowing to the east so the wind direction is WEST

Due to Earth’s Rotation on its Axis

Wind Speed Wind Speed- the rate at which wind moves in knots or mph Large difference in air pressure= strong winds Small difference in air pressure = weak winds Example: Sea Breeze on a sunny summer day!

Clouds, Precipitation and Dew Point Q. How do clouds form? A. Clouds form when air is cooled to the dew point and water condenses into tiny water droplets or ice crystals. In-order for water vapor to condense it must have a surface to condense on. These surfaces are known as condensation nuclei. Some examples of this are dust or ice.

Clouds, Precipitation and Dew Point Q. How does precipitation occur? A. Once the water droplets or ice crystals are too large they fall to the ground as precipitation. They type of precipitation depends on the atmospheric conditions in the clouds and on the ground! Example: Rain falls when the temperatures are above freezing while snow falls when the temperatures are below freezing!

Clouds, Precipitation and Dew Point Dew Point- the temperature at which water vapor condenses out of the air because the air is saturated Different types of clouds form depending on the altitude and conditions Dark= Precipitation

Examples of Clouds Cirrus- High wispy clouds Cumulus- low puffy clouds Cumulonimbus- tall dark thunderstorm clouds Stratus-flat low clouds (gloomy)

Field Maps and Isolines Field Map- a region of space that has a measurable quantity or value at every point The meteorologists then connect points with the same values… These lines with the same field value are known as isolines.

Isobars Isobars- lines of equal air pressure

Isotherm Isotherm: lines of equal temperature GENERAL RULE: As latitude increases temperature decreases

Air Masses and Fronts Air Mass- air with generally uniform characteristics Source Region- the surface over which an air mass forms Front- The boundary (on the ground) between two air masses

Air masses are classified based on their and amount of

Air masses get their characteristics based on

The abbreviations used to classify air masses use the following letters: c, m, T, P, and A. For each letter, describe its property: WordMeans c m maritime T P A continentdry moist Tropicalwarm Polarcold Arcticvery cold

Label

mT- Low Pressure cP- High Pressure

Air Masses and Fronts Air masses typically move from WEST to EAST across the United States. –The weather that occurred in Chicago today will be in New York tomorrow! Front- the line on the ground marking the boundary between two air masses

Cold Fronts Cold Front- the ground location where a cold air mass advances against a warmer air mass. The cold air mass is denser so it forces the warm up rapidly. –This causes the warm air rise, expand and cool. –This rapid condensation leads to heavy rain and/or thunderstorms. –The temperature drops rapidly as a cold front passes!

Explain what is happening below:

Warm Fronts Warm front- where a warm air mass pushed up and over a cold air mass. –The warm air goes over the cold air gradually because it is less dense than the cold air. –As the warm air rises it expands, and cools. –This causes condensation to occur over a wide gently sloping boundary. –This results in thick clouds and widespread precipitation.

Explain what is happening below:

Extreme Weather (Storms) Cyclone- any inward and counterclockwise air circulation around a low pressure center

Hurricane: Are huge cyclonic storms (Low Pressure systems) that form in the summer over warm ocean water. Energy comes from the sun as it evaporates water to fuel the hurricane! The wind blows counterclockwise around the center!