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Meteorology – the study of atmospheric phenomena. “Meteor” means high in the air Primary types Hydrometeors Cloud droplets Forms of precipitation Lithometeors Smoke, haze, and dust Electrometeors lightning. Weather vs. Climate. Weather - The current state of the atmosphere.
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“Meteor” means high in the air • Primary types • Hydrometeors • Cloud droplets • Forms of precipitation • Lithometeors • Smoke, haze, and dust • Electrometeors • lightning
Weather vs. Climate • Weather- The current state of the atmosphere. • Short term variations • Climate- Long term variations in the atmosphere. • Averaged over 30 years or more.
Words the Weatherman Uses • What words does the weatherman use to describe the weather?
Temperature • Temperature – measurement of how rapidly or slowly molecules move around. • The faster they are moving, the higher the temperature
What to Wear? • If you heard on the news in the morning, “Today the high will be 30 degrees” how would you dress?
It depends! • If you the temperature were in Fahrenheit, you would want to be this young lady • However, if the temperature were in Celsius, you would want to actually be this guy! (30°C = 86°F!) • And, if the temperature were in Kelvin…you would not be alive! (30 K = -458°F) • Moral of this story…always report in lab what temperature scale you are using!
Temperature versus Heat • Temperature and heat are different • Heat -The rate of transfer of energy that occurs because of a difference in temperature between two substances • Heat (or energy) flows from the object with the higher temperature to the object with the lower temperature. • How are heat and temperature different?
SOLAR FUNDAMENTALS • The sun is the source of all energy in the atmosphere. • This energy is transferred to Earth and throughout the atmosphere in three ways: • Radiation • Conduction • Convection
What is Radiation? • Radiation is the transfer of energy through space by visible light, ultraviolet radiation, or other forms of electromagnetic waves. • Radiation is named by the length of its wavelength. We only see a very small part of the spectrum. The part we experience as “heat” is the infra-red portion of the spectrum.
Which of these pictures is of our sun? X-Rays Ultraviolet Ultraviolet Radio and Microwaves Infrared Visible
RADIATION • Earth is continuously absorbing radiation, but it is also continuously sending it back into space. • 35% is reflecting back into space; 15% is absorbed by the atmosphere; only 50% is absorbed by the earth. • Absorption depends on the physical characteristics of the area and also the amount of solar radiation it receives. • For example: • Water vs. Land • Darker Objects vs. Light Objects
CONDUCTION AND CONVECTION • Solar radiation does not heat the air directly. • Solar energy that passes through our atmosphere is in the form of short waves (mostly light waves). • Energy that is radiated from the Earth is infra-red radiation. • These long waves can not pass through the Earth’s atmosphere because they are absorbed. • This energy is absorbed by the atmosphere and warms the air through the processes of conduction and convection.
CONDUCTION • Conduction is a type of energy transfer that occurs when molecules collide. • It only occurs when molecules are in contact with each other.
CONVECTION • Convection is the transfer of energy by the flow of a heated substance. • In the atmosphere, warm air becomes less dense and rises, it then cools and sinks, and the process begins again. • These air movements are called convection currents, which are ultimately responsible for weather.
Measuring Temperature • Temperature is measured in three different scales: • Fahrenheit (F) • 32 degrees is freezing, 212 degrees is boiling, -523 is absolute zero • Celsius (C) • 0 degree is freezing, 100 degrees is boiling, -273 is absolute zero • Kelvin (K) • 273 K is freezing, 373 is boiling, 0 is absolute zero **Absolute zero is the temperature that the molecules stop moving**
Moisture in the Atmosphere • How much water is in this room? • Meteorologists use 2 ways to describe moisture: • Dew Point • Relative Humidity
Relative Humidity • Humidity – the amount of water vapor in the air • Relative humidity – the amount of water vapor relative (or compared to) the total amount that the air can “hold” • Air with a higher temperature can “hold” more water vapor. • Relative humidity ranges from 0 to 100 percent. (100 percent = saturated = air has reached the dew point)
Dew Point • Dew Point – the temperature to which air must be cool at constant pressure to reach saturation or the maximum amount of water vapor there can be • The absolute way of measuring how much water vapor there is in the atmosphere is by using the dew point. (A dew point of 70 degrees Fahrenheit has more water vapor than a dew point of 50 degrees Fahrenheit) • Condensation occurs at this temperature – the water vapor changes into liquid water droplets
Which way of measuring humidity do you think is more helpful?
Air Pressure and Density • Air pressure = force exerted by air molecules • Pressure is measured in millibars (mb) • Pressure decreases as you move up through the atmosphere because there are less and less gas particles exerting pressure
Wind • Wind is the movement of air • Air moves from areas of high density to areas of low density to correct the imbalance. • Unequal heating of different surfaces causes wind during the day. • Wind has a speed and a direction. • Speed is in mph or knots • Direction is where is comes from.
Reading a Station Model • All your weather information in one place!
Pressure, Temperature and Density are Related! • T = Temperature , P = Pressure, D = Density • T , P , D • T , P , D • Table 11-2 on page 280 in your textbook shows a great summary of this information.
