Meteorology Chapter 3

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 temperatures 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 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 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 consists 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.