Chapter 5: Weather Only Section 1: What is Weather? Find the definitions of: Meteorology, meteorologist, weather, climate Not in book? Use the dictionaries
**Meteorology - Meteorology is the study of the atmosphere and its effects on our weather **Meteorologist - A meteorologist explains the earth's atmospheric phenomena and how the atmosphere affects the planet.
Weather is the state of the atmosphere at a specific time and place. Ex: today is raining Climate average weather pattern in an area over a long period of time. Ex: Washington is humid during summer
RADIATION FROM THE SUN IS THE DRIVING FORCE OF WEATHER AND CLIMATE Sun warms up the Earth, creating areas with different temperatures, different densities and different air pressures, Differences in Temp, Density and Air Pressure will be responsible for the movement of air and water, that affects climate and weather.
ATMOSPHERIC PRESSURE is the force exerted on any object on Earth, by the weight of the air molecules in the atmosphere above us.
WEATHER FACTORS: THE WEATHER FACTORS DESCRIBE THE WEATHER Wind Temperature Humidity Relative Humidity As a group, make a graphic organizer that includes all 4 weather factors and their definitions. To turn in at the end of class
WEATHER FACTORS: Wind air movement Temperature - It is the measure of the average amount of motion of molecules (how hot or cold an object is) Humidity - It is the amount of water vapor present in the air Relative Humidity - is the amount of water vapor present in the air compared to the amount of water vapor the air could hold at a specific temperature.
READ PAGES 120 AND 121 AND ANSWER: 1) what are the instruments used to measure wind? 2) What causes humidity? 3) How cam temperature affect humidity? 4) Explain the meaning of: The air is saturated 5) What is dew point?
What is wind and how can wind be measured? WIND IS AIR MOVEMENT Air will move from an area of high pressure ( colder air ) to an area of low pressure (warmer air) generating wind Wind can be measured: Anemometer Wind Vane and wind sock
**Devices to measure wind Anemometer measures wind speed Wind vane and wind sock will show the direction the wind blows
**TEMPERATURE It is the measure of the average amount of motion of molecules. OR ***Is the measure of how hot or how cold a substance is. It is measured with thermometers.
Humidity It is the amount of water vapor present in the air *** Humidity is caused by the Sun s heat that evaporates the water from the earth s surface
**Humidity depends on the Temperature *Higher Temperatures will bring higher humidity more evaporation *Lower Temp. less humidity less evaporation Evaporation- water turns into water vapor
Humidity **Air Saturation occurs when the air can t hold anymore water vapor, so the water vapor condenses, turning back into water When the air is saturated and condensation occurs, we have dew and frost
**Humidity *In higher temperatures air can hold more water. *At higher temperature, more water molecules are needed to saturate the air. (because the molecules expand)
Relative Humidity Relative humidity is the amount of water vapor present in the air compared to the amount of water vapor the air could hold at a specific temperature. **If the Air is saturated: *It can t hold any more water. *The amount of water vapor needed for saturation is reached. *The Relative humidity is 100%
What does it mean that the Relative Humidity is 50%????
Relative Humidity **If you hear a weather forecaster say that the relative humidity is 50 %, it means that the air contains 50% of the water needed for the air to be saturated. **Remember: when the air is saturated, the Relative humidity is 100%
*** TO MEASURE RELATIVE HUMIDITY WE USE HYGROMETERS
What is Dew Point?
**Dew Point The dew point is defined as the temperature at which air is saturated and water vapor begins to condense. **Water vapor will condense because the air is saturated and can t hold anymore water vapor. So the water vapor turns into water.
**Notes: Why do we have Dew or Frost in the morning, temperature drops the amount of humidity that the air can hold decreases ( warmer air can hold more water vapor) so the extra moisture will condense forming dew or frost
***Dew, Frost and Fog **Dew - When surface temperature drops, eventually reaching the dew point, atmospheric water vapor condenses to form small droplets on the surfaces. ** Frost - When temperatures are near 0 C, dew takes the form of ice and is called frost. ** Fog Is a cloud very low, near the ground
PRECIPITATION Read page 123 and 124 and answer: What is precipitation? What is necessary to happen for precipitation to occur? What determines what type of precipitation will be formed? Explain why sometimes we have precipitation in form of rain (liquid) or in solid or semi-solid form.
Precipitation water falling from clouds occurs when cloud droplets combine and grow large and heavy enough to fall to Earth.
The type of Precipitation depends on the air temperature. 1) If the temperatures are above freezing - rain. 2) If the temperatures at the freezing point or below solid precipitations Sleet, hail and snow
BIGGEST PIECE OF HAIL EVER RECORDED IN THE USA SOUTH DAKOTA 2010 Diameter - 8 inches Circumference - 18.62 inches Weight - 1 pound and 15 ounces
Youtube video: Calculating Dew Point and Relative Humidity https://www.youtube.com/watch?v=ozh9ksay9kc Worksheet Lab
CLOUDS ***Definition: A cloud is a large collection of very tiny droplets of water or ice that floats in the air.
**How do clouds form? Clouds form as warm air is forced upward, expands and cools. If the relative humidity reaches 100%, the air is saturated and will condense forming tiny droplets. The droplets are suspended in the air forming the clouds
THERE ARE DIFFERENT TYPES OF CLOUDS. CLOUDS ARE CLASSIFIED ACCORDING TO THE SHAPE AND THE POSITION IN THE ATMOSPHERE (HEIGHT)
Chapter 5 Section 2 : Weather Patterns
AIR MASS Large body of air. Its properties will change depending on where it develops. It will be: Warm if it forms over warm land More humid if it forms over water **** Movement of air masses are responsible for weather changes
AIR MASSES THAT AFFECT THE USA See Fig 9 on page 126
**HOW ATMOSPHERIC PRESSURE AFFECTS WEATHER: Low pressure areas are usually cloudy areas air rises and cools water vapor condenses forming clouds, possibility of precipitation. High pressure areas have sinking air masses, the air can t rise, there will be no cloud formation, which means good weather.
Fronts - A transition zone between two air masses of different density, moisture, or temperature. Cloudiness, precipitation, and storms sometimes occur in these areas. Four types of fronts: cold, warm, occluded, and stationary and how they are represented in weather maps.
COLD FRONT COLD AIR SLIDES UNDER THE WARM AIR WARM AIR RISES CAUSING PRECIPITATION
WARM FRONT: WARM AIR SLIDES ON TOP OF COLD AIR, FORMS A SLOPE ON TOP OF COLD AIR CAUSING PRECIPITATION
OCCLUDED WARM AIR TRAPPED IN BETWEEN BOTH FRONTS - CAUSING PRECIPITATION
STATIONARY: FRONTS MOVE IN OPPOSITE DIRECTION UNTIL THEY MEET AND CAN T ADVANCE FOR A WHILE RAIN FOR SEVERAL DAYS
Table of Contents Chapter: Weather Section 3: Weather Forecasts
Weather Observations A meteorologist is a person who studies the weather A meteorologist gathers information and predicts weather Keep in mind conditions can change very quickly mistakes in weather prediction are not uncommon
Measurements of: temperature, air pressure, winds, humidity, and amount of precipitation. Devices needed to predict weather Devices used to predict weather: Computers, weather satellites, radars, and instruments attached to balloons are used to gather data.
WEATHER BALLOONS CARRY WEATHER INSTRUMENTS THAT MEASURE TEMPERATURE, PRESSURE, HUMIDITY, AND WINDS IN THE ATMOSPHERE.
Radar is an object with a detection system that uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.
Station Model is a illustration that shows the weather occurring at a certain area.
To build Station Models and Weather Maps, meteorologists use symbols accepted internationally to represent: air pressure temperature wind Station Models and Weather Maps cloud cover Precipitation Textbook page 794
Station Model:
On Weather maps there are more than one station model and also: Isotherms Isobars Areas with high or low pressure
Isotherms Weather maps have lines called isotherms that connect locations of equal temperature Iso means same therm means temperature.
Isobar is a line drawn to connect points of equal atmospheric pressure. air pressure is often given in millibars Barometer is used to measure air pressure.
Weather Maps On a weather map, pressure areas are drawn as circles with the letters H or L or the words High or Low in the middle of the circle.
HIGH X LOW PRESSURE