Meteorology

What is Meteorology? Meteorology is the study of atmospheric phenomena Anything that’s high in the sky: raindrops, rainbows, dust, snowflakes, fog and lightning All of these are examples of meteors?

What is Meteorology? Atmospheric phenomena are classified as types of meteors Cloud droplets (rain, sleet, snow) are types of hydrometeors. Smoke, haze, dust – any particles suspended in the atmosphere are lithometeors.

What is Meteorology? Short term variations in atmosphere phenomena that affect the environment and life on Earth is weather. These variations can be minutes, hours, days, weeks up to years long. Climate is the long term average in weather for a particular area

Heating Earth’s Surface Sunlight is always heating some part of Earth Over time the amount of thermal energy Earth gets is the same amount that Earth radiates back to space. How is this solar radiation distributed around Earth?

Imbalanced Heating In January, which is warmer? Miami or New York City? One reason is that Earth is tilted. Miami gets more solar radiation in January. Another is that Earth is a sphere and different places are at different angles to the sun.

Thermal Energy Redistribution Places on Earth maintain about the same average temperatures over time due to the movement of air and water between land, water and atmosphere.

Air Masses An air mass is a large volume of air with the same humidity and temperature as its source region. A source region is the area where an air mass forms. Most form over tropical waters or polar regions.

Types of Air Masses Tropical air masses form in tropical bodies of water and are responsible for our hot, humid summers Polar air masses form over the cold waters of the North Atlantic and North Pacific. These bring our really cold air in winter. The flip side?

Learning Targets Compare and contrast weather vs climate Analyze how imbalances in the heating of Earth’s surface create weather Identify five types of air masses and explain how air masses form

Global Wind Systems If the Earth didn’t rotate, two large convection currents would cover the Earth. Colder air would sink to the tropics where it would force warm air to rise. This air would cool as it got higher and on and on

Global Wind Systems Earth rotating from west to east prevents this from happening. The directions of our winds are influenced by the Earth’s rotation. Its called the Coriolis effect.

Coriolis Effect Causes fluids and objects to move in a curved path. Moving air curves to the right in the northern hemisphere Moving air curves to the left in the southern hemisphere http://www.youtube.com/watch?v=mcPs_OdQOYU

Global Wind Systems The Coriolis effect and the heat imbalance on Earth create distinct global wind systems. There are three main zones or wind systems: polar easterlies, prevailing westerlies and trade winds.

Global Wind Systems Polar easterlies Between 60o N latitude and the north pole and 60o S latitude and the south pole Begin as dense polar air that sinks As the Earth spins, this cold air is deflected in an easterly direction: usually weak and sporadic

Global Wind Systems Prevailing westerlies Found between 30oN and 60oN and 30oS and 60oS Surface winds move toward the poles in a westerly direction (again due to the Earth’s rotation) These move much of the weather across the US

Global Wind Systems Between the polar easterlies and the prevailing westerlies lie an area called the polar front. This can bring stormy weather to us.

Global Wind Systems Trade winds are between 30oN and 30oS These circulation belts move toward the equator in an eastern path

Jet Streams Atmospheric conditions and events that happen at the boundaries between wind zones strongly influence our weather. On either side of the boundaries, surface air and upper level air differ in temperature and pressure.

Jet Streams The difference in air pressure at the boundaries causes wind. Wind is the movement of air from an area of high pressure to an area of low pressure.

Jet Streams A large temperature gradient in upper level air combined with the Coriolis effect gives us strong westerly winds called jet streams. Jet streams are narrow bands of fast moving winds. Its speed varies with the temperature differences..

Jet Streams The position of the jet stream varies with the season. Its usually found in the region of strongest temperature differences on a line from the equator to a pole. It is the strongest core of winds. http://www.youtube.com/watch?v=CgMWwx7Cll4

Types of Jet Streams Polar jet streams separate the polar easterlies from prevailing westerlies; the major jet stream Weaker jet streams are subtropical jet streams; found where trade winds meet prevailing westerlies Most storms form along jet streams and bring large scale weather systems

Fronts A collision of two air masses is a front; a narrow region between two air masses of different densities Fronts can cover thousands of square miles

Cold Fronts Cold front: cold, dense air displaces warm air Less dense warm air rises, cools and condenses: intense precipitation occurs A blue line with evenly spaced blue triangles is a cold front on a weather map

Warm Front Advancing warm air displaces cold air Can cause widespread light precipitation A red line with evenly spaced red semicircles

Stationary Front Two air masses meet but neither advances; the boundary between them stalls A line of evenly spaced, alternating cold and warm symbols pointing in opposite directions

Pressure Systems Low Pressure Air from outside replaces rising air, this air spirals inward to the center and then up in a counter clockwise direction Rising air cools and condenses into clouds and precipitation

Pressure Systems High pressure systems Sinking air moves away from the system’s center Coriolis effect causes sinking air to move to the right, making air circulate in a clockwise direction in our hemisphere Fair weather

Learning Targets Compare and contrast the three major wind systems Identify four types of fronts and differentiate between each

Gathering Weather Data Meteorologists measure atmospheric conditions such as Temperature Air pressure Wind speed Relative humidity Two important factors in weather forecasting are the accuracy of the data and the amount of data available

Tools for measuring atmospheric conditions A thermometer measures temperature in F or C. A barometer measures air pressure. An anemometer measures wind speed. A hygrometer measures humidity.

Thermometers Usually some type of glass tube containing a liquid. When heated the liquid expands when causing the column of liquid to rise. When the liquid cools, the column drops.

Barometer Some have a column of mercury in a glass tube. Changes in air pressure change the height of the mercury.

Anemometer The simplest has four cupped arms positioned at right angles from each other. The arms rotate when the wind blows. The wind’s speed is calculated by the number of revolutions of the cups over a specific period of time

Hygrometer Some have a wet bulb and a dry bulb thermometer and requires a conversion table to calculate. The National Weather Service uses an automated surface observing system to gather data 24 hours a day

Data From the Upper Atmosphere Weather is largely the result of conditions in the upper atmosphere. An instrument that measures those conditions is a radiosonde. Contains a package of sensors suspended in a balloon that enters the upper atmosphere that collect data

Weather Radar Radar stands for radio detection and ranging It generates radio waves and transmits them through an antenna at the speed of light. The waves reflect when they hit particles (rain)

Doppler Radar Doppler effect is the change in pitch or frequency that occurs due to the relative motion of a waves. Doppler radars measure the speed of precipitation as it moves toward and away from the radar.

Weather Satellites Some satellites move high above the earth using infrared imagery to make observations at night. The imagery can detect differences in frequencies to map cloud cover or surface temperatures.

Weather Satellites Other satellites use visible light to photograph Earth. These photos are sent back to weather stations to analyze cloud cover.

Learning Targets Discuss the importance of accurate weather data Summarize the instruments used to collect weather data from Earth’s surface Analyze the strengths and weaknesses of weather radar and weather satellites

Surface Weather Analysis Weather reports are generated from the data received from radars and satellites. Station models A record of weather data for a specific spot at a particular time Symbols are used to represent the weather data The symbols allow for the reporting to be uniform

Surface Weather Analysis Plotting station model data To plot data nationally meteorologists use lines to connect points of equal or constant values Lines of equal pressure are called isobars Lines of equal temperature are called isotherms

Interpreting Station Model Data Using isobars, isotherms, and station model data, meteorologists can analyze current weather conditions.

Types of Forecasts Digital forecasts Analog forecasts Created by applying physical properties and math to atmospheric variables and then making a prediction Analog forecasts Based on comparing current weather patterns with weather patterns of the past

Short Term Forecasts The most accurate of all forecasts because weather conditions are fluid and change over time

Long Term Forecasts Forecasts for months or seasons are based on weather cycles or patterns. Forecasts of 5 to 7 days are made using upper level atmospheric measurements and patterns.

Learning Targets Analyze a basic surface weather chart Distinguish between digital and analog forecasting Describe problems with long term forecasts