Weather and climate chapter 3
isotherm
a line connecting points of equal air temperature
growing degree-days
a practical application of temperature data for determining the approximate date when crops will be ready for harvest.
liquid-in-glass thermometer
a simple instrument that provides relatively accurate readings over a wide temperature range.
Celsius scale
a temperature scale devised by Anders Celsius in 1742 and used where the metric system is in use. For water at sea level, 0 degrees is designated the ice point and 100 degrees the steam point.
Fahrenheit scale
a temperature scale devised by Gabriel Daniel Farenheit in 1714 and used in the English system. For water at sea level, 32 degrees is designated the ice point and 212 degrees the steam point.
Kelvin or absolute scale
a temperature scale used primarily for scientific purposes and having intervals equivalent to those on the Celsius scale but beginning at absolute zero.
bimetal strip
a thermometer consisting of two thin strips of metal welded together, which have widely different coefficients of thermal expansion. When temperature changes, the two metals expand or contract unequally and cause changes in the curvature of the element.
maximum thermometer
a thermometer that measures the maximum temperature for a given period in time, usually 24 hours. A constriction in the base of the glass tube allows mercury to rise but prevents it from returning to the bulb until the thermometer is shaken or whirled.
minimum thermometer
a thermometer that measures the minimum temperature for a given period of time, usually 24 hours. By checking the small dumbbell-shaped index, the minimum temperature can be read.
annual mean temperature
an average of the 12 monthly means.
thermistor
an electric thermometer consisting of a conductor whose residence to the flow of current is temperature dependent; commonly used in radiosondes.
thermometers
an instrument for measuring temperature; in meteorology, generally used to measure the temperature of the air.
thermograph
an instrument that continuously records temperature.
cooling degree-day
each degree of temperature of the daily mean above 65 degrees F is counted as one cooling degree-day. The amount of energy required to maintain a certain temperature in a building is proportional to the cooling degree-days total.
heating degree-days
each degree of temperature of the daily mean below 65 degrees F is counted as one heating degree-day. The amount of heat required to maintain a certain temperature in a building is proportional to the heating degree-days total.
controls of temperature
factors that cause temperature to vary from place to place and from time to time.
fixed points
reference points, such as the steam point and the ice point, used in the construction of temperature scales.
specific heat
the amount of heat needed to raise the temperature of 1 gram of a substance 1 degrees Celsius
temperature gradiant
the amount of temperature change per unit of distance.
daily temperature range
the difference between the maximum and minimum temperatures for a day.
annual temperature range
the difference between the warmest and coldest monthly means.
daily mean temperature
the mean temperature for a day that is determined by averaging the hourly readings or, more commonly, by averaging the maximum and minimum temperatures for a day.
monthly mean temperature
the mean temperature for a month that is calculated by averaging the daily means.
ice point
the temperature at which ice melts
steam point
the temperature at which water boils
absolute zero
the zero point on the Kelvin temperature scale, representing the temperature at which all molecular motion is presumed to cease.