Chapter 3 Study Guide

Key Terms

radiational cooling: The process by which Earth’s surface and adjacent air cool by emitting infrared radiation.

radiation inversion: An increase in temperature with height due to radiational cooling of Earth’s surface. Also called a nocturnal inversion

Freeze: A condition occurring over a widespread area when the surface air temperature remains below freezing for a sufficient time to damage certain agricultural crops. A freeze most often occurs as cold air is advected into a region, causing freezing conditions to exist in a deep layer of surface air. Also called advection frost.

thermal belt: Horizontal zones of vegetation found along hillsides that are primarily the result of vertical temperature variations.

orchard heater: Oil heaters placed in orchards that generate heat and promote convective circulations to protect fruit trees from damaging low temperatures. Also called smudge pots.

wind machine: Fans placed in orchards for the purpose of mixing cold surface air with warmer air above.

daily (diurnal) range of temperature: The difference between the maximum and minimum temperatures for any given day.

mean (average) daily temperature: The average of the highest and lowest temperature for a 24-hour period.

controls of temperature: The main factors that cause variations in temperature from one place to another.

Isotherm: A line connecting points of equal temperature.

annual range of temperature: The difference between the warmest and coldest months at any given location.

mean (average) annual temperature: The average temperature at any given location for the entire year.

heating degree day: A form of the degree day used as an index for fuel consumption.

cooling degree day: A form of degree day used in estimating the amount of energy necessary to reduce the effective temperature of warm air. A cooling degree-day is a day on which the average temperature is one degree above a desired base temperature.

growing degree day: A form of the degree day used as a guide for crop planting and for estimating crop maturity dates.

sensible temperature: The sensation of temperature that the human body feels in contrast to the actual temperature of the environment as measured with a thermometer.

wind-chill index: The cooling effect of any combination of temperature and wind, expressed as the loss of body heat. Also called wind-chill factor.

Frostbite: The partial freezing of exposed parts of the body, causing injury to the skin and sometimes to deeper tissues.

Hypothermia: The deterioration in one’s mental and physical condition brought on by a rapid lowering of human body temperature

liquid-in-glass thermometer: An instrument for measuring temperature. The most common is liquid-in-glass, which has a sealed glass tube attached to a glass bulb filled with liquid

maximum thermometer: A thermometer with a small constriction just above the bulb. It is designed to measure the maximum air temperature.

minimum thermometer: A thermometer designed to measure the minimum air temperature during a desired time period.

electrical thermometer: Thermometers that use elements that convert energy from one form to another (transducers). Common electrical thermometers include the electrical resistance thermometer, thermocouple, and thermistor

Radiometer: An instrument designed to measure the intensity of infrared radiation emitted by an object. Also called infrared sensor.

bimetallic thermometer: A temperature-measuring device usually consisting of two dissimilar metals that expand and contract differentially as the temperature changes.

Thermograph: An instrument that measures and records air temperature.

instrument shelter: A boxlike (often wooden) structure designed to protect weather instruments from direct sunshine and precipitation.

Chapter 3 Study Guide Questions

1. When is Earth closest and farthest from the sun? Names for this.

     Earth is closest to to the sun during a point called perihelion, which occurs around January 3rd each year. Conversely, Earth is farthest from the sun at aphelion, occurring around July 4th.

2. Why do we have seasons? 

   1. The tilt of Earth's axis and its orbit around the sun cause the variation in sunlight received at different times of the year, resulting in the changing seasons.

3. What is the difference between a solstice and an equinox?

   • Seasons occur due to the tilt of Earth's axis as it orbits the sun.

   • A solstice marks the longest and shortest days of the year, while an equinox signifies the days when day and night are approximately equal in length.

4. Understand the diurnal temperature pattern on Earth and why the maximum daytime temperature occurs well after noon on most days

   This phenomenon is due to the time it takes for the Earth's surface to absorb heat and subsequently release it, resulting in a lag between peak solar radiation and the highest temperature recorded. This lag is influenced by various factors, including the specific heat capacity of the materials on the Earth's surface and atmospheric conditions.

5. What is a temperature inversion?  Where do we most commonly see them?

   A temperature inversion occurs when a layer of warm air traps cooler air near the Earth's surface, preventing it from rising. This phenomenon is most commonly observed in valleys and urban areas, particularly during the night or early morning when the ground cools rapidly.

6. Understand the basics about the main controllers of surface temperature: Latitude, Proximity to Water, Ocean Currents, Elevation.

   These factors play crucial roles in determining climate patterns and local weather conditions.

   • Latitude: Affects the angle of sunlight received, influencing temperature and seasonal variations.

   • Proximity to Water: Coastal areas tend to have milder temperatures due to the moderating influence of large bodies of water.

   • Ocean Currents: Warm and cold currents can significantly affect coastal climates, redistributing heat across the planet.

   • Elevation: Higher altitudes generally experience cooler temperatures, leading to variations in climate even over short distances.

7. What are the heat index and wind chill?

   1. The heat index is a measure that combines air temperature and humidity to determine the apparent temperature, or how hot it feels to the human body, while wind chill refers to the perceived decrease in temperature felt by the skin due to the flow of air, which can make cold temperatures feel even colder. Understanding these concepts is crucial for interpreting weather forecasts and preparing for temperature fluctuations.

8. How does a thermometer work? Alcohol vs. Mercury

   1. Alcohol thermometers use colored alcohol that expands and rises in a glass tube as the temperature increases, providing a visual indication of the temperature.

   2. Mercury thermometers contain mercury, which also expands with heat but is less safe due to the toxicity of mercury. Both types of thermometers are calibrated to provide accurate temperature readings in various settings.