2 13 03 lecture

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Cycles of Air Temperature Outline for Lesson 6 Temperature Measurements 2/13/03 World Distributions of Temperature


World Temperature Distributions World mean sea level temperature in January in °C. Isotherms trend east to west Q. Why ? A. Heating of the Earth’s surface and atmosphere is in large part a function of latitude. North South (Temperature)


World Temperature Distributions World mean sea level temperature in January in °C. Decreasing temperature toward the Poles Q. Why ? A. Heating of the Earth’s surface and atmosphere is in large part a function of latitude. (Temperature) North South Hot Cold Cold


World Temperature Distributions World mean sea level temperature in January in °C. World mean sea level temperature in July in °C. Hot and Cool “spots” continuously migrate south from June 21-22 until Dec 22-23 them migrate north from Dec 22-23 until June 21-22. Q. Why ?


The “hot spots”on the temperature plot migrate with latitude, as does the position where the Sun’s rays are 90° overhead. Equator 23.5° N 23.5° S Migration of position where sun’s rays are 90° overhead Tropic of Cancer Tropic of Capricorn


The higher the angle of the sun the more solar radiation to heat the Earth and atmosphere.


The hottest and coldest places are over land. Warm ocean currents moving to the Poles warm the air. Equatorial bound currents Help cool the air. World Temperature Distributions


World mean sea level temperature in January in °C. World mean sea level temperature in July in °C.


Comparison of solar noon sun angles for for the summer and winter solstice. Another way to think about the effect of latitude on temperature data


Cycles of Air temperatures “Its hot in the day and cold in the night!!….” –Public Enemy The daily cycle of incoming solar radiation, earth’s radiation And the resulting temperature cycle. Midday, Equinox. Rate of outgoing exceeds the rate Of incoming. Rate of incoming exceeds the rate of outgoing.


Annual Temperature Variations The months of the year with the highest and lowest temperatures do not coincide with the months receiving the most or lowest radiation. The other processes which also control temperature (i.e. winds and surface ocean currents do not happen instantaneously. There is a “lag time”.


Urban heat islands have been created over time here in the United States and around the world. In Baltimore, Phoenix, Tucson, Washington, Shanghai, and Tokyo, for example, scientific data show that July's maximum temperatures during the last 30 to 80 years have been steadily increasing at a rate of one-half to one degree Fahrenheit every ten years. In these cities, the temperature on the hottest summer day is rising by up to 1°F each decade.


The Heat Island Effect (Washington DC) Changes in the earth’s surface when vegetated areas are transformed to asphalt . Tall buildings and Concrete have a higher specific heat than vegetation and soil Rapid runoff of rainwater reduces the amount of energy consumed by evaporative cooling. Heat that would have gone to convert liquid water to water vapor is goes toward increasing the surface temperature. Average Minimum Temperatures (Dec-Feb)


Data from table 3-D on page 74


Higher temperatures in urban heat islands results in increased energy use, mostly due to a greater demand for air conditioning. As power plants burn more fossil fuels, they increase both the pollution level and energy costs.


As temperature rises, so does the likelihood that ozone (and smog) will exceed the national standard.


Bimetal strips are often used to construct thermographs. A type of thermometer with two metal strips connected together. The two metals expand at drastically different rates when heated which causes the stripe to bend. The bending moves the pen up and down the roll of graph paper


Thermograph plot of temperatures for Peoria Illinois, during a seven-day span in May 1992. Temperature typically reaches a maximum in the afternoon, however, a weather event results in a cooling trend that results in the maximum being observed near midnight. - Maximum temperatures observed. Maximum Temperature in the afternoon - Minimum temperatures observed. Cooling trend.. Perhaps a “cold front”


Temperature Measurements Mechanical Thermometers Temperature rises, molecules in the fluid grow more expansive and rise in the column. Have to account for optical distortions created by the meniscus….calibrate it with a known standard


Special thermometers have been developed to record the maximum and minimum temperatures.


Electrical Thermometers -thermistor (thermal resistor) is a stripe of metal which varies its resistance to a current flow with temperature. As temperature goes down the resistance decreases temperature goes up and the resistance increases. various thermistors


Temperature Scales Fahrenheit Celsius Kelvin All temperature scales need reference points. The freezing and boiling point of water are convenient.


How to convert between the different scales. °F = (1.8 x °C) + 32 or °C = (°F-32)/1.8 The interval between the boiling and freezing point is 100 degrees on the Celsius scale and 180 between on Fahrenheit scale. 180/100 = 1.8 F to C: C to F:


Kelvin Scale Degrees Kelvin are called Kelvins. The divisions are exactly the same as Celsius. The reference points are different however, 373 K is the boiling point and 273 is the freezing point. The unique reference point for Kelvin is point at which all molecular motion is presumed to stop.


Chapter 4 Moisture and Atmospheric Stability Movement of Water through the Atmosphere Waters Changes of State


Movement of Water through the Atmosphere


It is the Atmosphere which links the Oceans to the Land. Even though the amount of water in the atmosphere at any time is only a fraction if the total Earth’s total hydrosphere, it is the rapid exchange taking place that creates what we call weather. How fast is the exchange? It is estimated that over North America, almost six times as much water is carried within the atmospheric currents than is transported in all the rivers in the continent.


Energy is absorbed or released from the atmosphere during the exchange. The energy that is liberated helps to drive the “weather machine”

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